Managing damp problems in old buildings

Home Damp and Condensation Managing Damp in Old Buildings

Managing Damp in Old Buildings

It's inevitable that you will find dampness somewhere in an old house. Nothing lasts forever, but despite English weather, our old buildings stand the test of time better than any modern house. The worst enemy of old houses is we humans - it's what we do to them, or fail to understand about them, that causes problems and makes you think you have to 'Damp Proof'. Almost 100% of damp issues in buildings are caused by condensation, and lack of adequate ventilation.

If the only thing I can teach you on this website is to understand the difference between water as a gas, and water as a liquid, and how temperature drives this difference, then I've done my job. So: Read through this introduction, and start to get your head around the building blocks of damp problems and their solutions. None of it is rocket science - but as you explore the internet, you will find that vast amounts of complete rubbish and scientific nonsense has been written, and continues to be written - most of it in an attempt to sell either chemicals or widgets. This website is dedicated to blowing that rubbish out of the water, and giving you a sound basis on which to learn about your home, how it works, where damp comes from, why it is there, and how to deal with it.

The Best Selling book we've written, The Warm Dry Home is the complete guide to understanding and solving problems with Dampness and Mould.

Let's look at some basic blocks then:

What is an old building?
What is 'damp'?
What actually is water?
How does temperature come into the picture?
Armed with this knowledge, how do we end up with a warm dry house?

What is an 'old building'?

The Official Definition of an Old Building used to be "Built before 1919". That didn't really help anyone understand what made them different. It's now defined as:

"A solid walled structure, built using breathable materials, which needs to breathe"

This definition very deliberately talks about breathability. It is the cornerstone of the whole concept of old buildings and architecture. It may sound a bit daft, but until the last War, most materials used in buildings are fairly simple - timber, stone, brick, lime based mortars and plasters, and stone or slate tiles. All of these materials had one thing in common - breathability. It is since the war that there has been an exponential explosion in building materials, there are now thousands of them, and most are artificial compounds - gypsum plaster, cement, plastic sheets and membranes, silicones, epoxy resins, polyurethane insulation sheets, fibreglass, plastic coatings and paints.. the common thread to all of these is that they are NOT breathable. Use them on an old building, and it will get wet.

What is 'damp'?

Damp as most people know it, when applied to old buildings, is a collection of symptoms. Elsewhere in the site we go into depth about these, but essentially: hollow plaster, stains on walls, flaky paint, rotting skirtings, salty fluff on walls, dark patches on walls, plaster falling off, damp smells, mould and mildew, and no.. damp doesn't Rise, and no, there is no such thing as Rising Damp. These are SYMPTOMS - they are just evidence of something happening which in 99% of cases, YOU can easily do something about. ~They are ALL to do with water in the air, and the temperature of both the air, and the wall that shows the symptoms.

What actually is Water?

You think of water as something in a glass, pouring out of a tap, as rain, or a river. But you are constantly immersed in water - as a gas. You just don't know it. You can't see it. And it's everywhere. Water as a gas is a tiny molecule - its like a naughty child - small, fast moving, high energy, gets everywhere, but doesn't actually do much damage! When you cool it down, it loses energy, slows down and becomes a liquid - initially as minute droplets, and if there's enough of them, they clump together to form a liquid. The problem now is that the liquid molecules are very big, and they can't get out of non-breathable materials like cement, gypsum plaster and plastic paints. This is where our problems stem from: Gaseous water moves easily through stone, brick, concrete, gypsum, wood, many plastics - but if you cool those down, water as gas turns into a liquid and your wall gets wet - inside. THAT is what they call 'rising damp' and THAT is what causes all the flaky plaster and paint.

How does Temperature come into the picture?

There is a bit of science involved here. If you cool air that contains water as a gas (in air spaces within your walls for example) it condenses when it reaches the 'Dew Point'. The scientific bit is predicting the dew point temperature. This is governed by the Saturation of the air at a given temperature (Relative Humidity) but most importantly, the actual amount of water dissolved in the air at that temperature (The Absolute - measured in Grams per Cubic Metre of air). In short, the warmer the air, the more saturated it is, the higher the Dew Point, and the more likely your walls are going to be wet inside.

Armed with this knowledge, how do we end up with a warm dry house?

By controlling the Dew Point, we can prevent condensation forming in the walls, and therefore create a dry house. To control the Dew Point, we have to monitor the total amount of water that's dissolved in the air - the Absolute. This is where it is vital to control moisture production in your home - cooking, showering, family life - all of these produce vast amounts of water - several gallons a day - and it is this water that ends up in your walls. All we have to do is control the sources of moisture, and introduce scientifically controlled ventilation to achieve a dry house - and dry walls don't transmit heat nearly as quickly as wet walls, so it's a warm house as well - win win!

Don't stop walls breathing!

Moisture diffuses through all building fabric (Walls, stone, mortar, plaster, paint, timber), regardless of temperature. This process of diffusion is known as 'Breathing' when applied to walls and other parts of the building fabric like the roof for example. It is shallow when there is little temperature variation and deepest when the daily range is greatest. Water always moves from where it is more concentrated to where it is less (humid to dry). If air within the wall is humid, and the wall cools below dew point then water vapour condenses as water droplets in the pores of the masonry (this is what Rising Damp actually is), though the wall may still appear ‘dry’. During warmer and drier times, some of this water will evaporate and leaves the wall. Even walls which seem dry will contain water, the amount varying with changes in the season and climate. If there are salts or other hygroscopic (moisture-attracting) materials in the masonry, the amount of water drawn into (and retained in) the wall can be sufficient to make the wall visibly damp, even in dry weather. This is the same as happens when you leave a pot of salt on the kitchen table - it gets wet.. Most of the time, the inside of a house will be 'wetter' than the air outside, because we humans produce a lot of water from living.

Anything that prevents a masonry wall from breathing will reduce its life expectancy. Coatings designed to seal the surface of masonry walls (and so ‘protect’ them) trap moisture behind the coating and cause a damp problem elsewhere, such as on the other side of the wall. If there are appreciable salts in the wall, damage caused by inappropriate use of coatings can be dramatic . Coatings themselves - cement renders, gypsum plasters, plastic emulsion paints - will eventually be forced off the wall. This is why we do NOT recommend products like Stormdry, Sandtex, Weathershield - all of which we have found to cause major problems of water entrapment on walls. More on 'Breathable Paints' here

Most problems of damp in pre-1920's buildings have been caused since the war, when cement and gypsum plaster became widely available - these two materials are responsible for over 90% of the damage that we see. They are impervious, they trap moisture and cause rot - they are death to an old house. Note that they all allow water to pass through them AS A GAS - but not as a liquid. Add silicone sealants to a timber frame, and you have instant rot of oak which is probably 400 years old. I have seen new timber frames start to rot in 2 or 3 years when incompetent framers seal the panels using mastic instead of oakum, which can breathe.

Homebuyer Surveys - not suitable for older buildings...

I am constantly inundated by people who are getting Homebuyer surveys, in which the 'Surveyor' recommends you get a 'specialist timber and damp survey from a PCA registered contractor'.

If a qualified surveyor - a Chartered member of RICS - tells you that an independent 'timber and damp' survey is required - I suggest you tell them you are not paying the bill. These people are incompetent. If they cannot diagnose the REAL reasons for damp in an old house - tell them to go survey a dolls house. Peter is Joint Author of the new RICS dampness diagnosis methodology, and anyone not knowing about this needs re-training!

As of 2020, the RICS Home Survey Standard is mandatory. This means that from now on, everything following on this page is illegal and out of the door for RICS surveyors - they NEED to show proper competence, and if they don't, they are in big trouble.

If they even MENTION Rising Damp - they are incompetent. Do NOT pay them.. Walk away from the survey, and get someone who knows about old buildings. Stephen Boniface, former chairman of the construction arm of the Royal Institution of Chartered Surveyors (RICS ), has told the institute’s 40,000 members that ‘true rising damp’ is a myth and chemically injected damp-proof courses (DPC) are ‘a complete waste of money’. Quite a number of my clients have sued surveyors - one emailed me to say the surveyor that told him he had rising damp has just settled out of court for £5000 in compensation. Another client in Wales told the very highly qualified surveyor where to shove his bill - the surveyor wrote a lengthy reply in which he explained that he has a lifetime of experience in diagnosing rising damp in houses all over the area - unfortunately we found out he'd previously surveyed this particular house, and was recommending the same treatment the second time around in as many years. You can imagine the response to his request for payment!

Do NOT let any building society or bank force you have any form of damp treatment before they approve a loan. If they do, contact us and we will stop this rubbish. Be aware that times are changing, and more and more people are questioning this ridiculous practise - it is only a matter of time before banks drop this expensive and unneccesary habit - but we all need to put pressure on them to stop it.

There are GOOD surveyors out there - RICS does train people - but there is such an entrenched belief in rising damp that entire industries are fed by it. A surveyor is required by RICS to state clearly whether they consider themselves capable of surveying an old house. You must ensure that if your house was built before around 1930, you ask that they clearly state this, and sign their survey that they consider themselves capable of surveying your type of house. RICS actually run a conservation course which helps equip their surveyors for the job - it is a great pity more people don't do the course! If they use a damp meter - throw them out. Aske them beforehand how they intend to measure dampness.

There is a MASSIVE problem of fraud, and incompetence in the Building Survey industry. If in doubt, do your research - you probably are... its why you are here...

This is the English Heritage Guidance document that covers almost all the points discussed here - hopefully, when you see the importance that EH gives the subject, you'll realise I am not just ranting on..!

English Heritage: Guidance concerning Energy Efficiency in Old Buildings

There's another good article here:

Building Conservation.com - Rising Damp

Rising Damp is almost non-existent - it rarely occurs naturally , and it CERTAINLY doesnt move a metre up the walls as 'damp proofing' 'specialists' would have you believe. We have built experimental walls with old, porous bricks, jointed with lime mortar. When the base of the wall is placed in water, the bottom row will get wet. Water is wicked up the brick, reaches the first mortar joint and evaporates. It rarely if ever goes beyond the first joint unless it is 'bridged' by having cement render slapped over the top of it. It certainly doesnt go the magical metre high that every rising damp salesman will claim. Do you know that it has NEVER been reproduced in a laboratory, despite many attempts to do so - even by the industry itself.

Injection Damp Proofing old houses is a WASTE of time and money - it doesnt work, and it causes irreparable damage to the fabric of your house
Damp Courses are almost NEVER broken, bridged or damaged, as damp proofing companies will always tell you
There is almost always a specific reason for damp, which is easily fixed
Do NOT be talked into hacking old plaster off and re-plastering with gypsum, or worse still, waterproofing compounds, or so called 'waterproofing or renovating plaster'!
Nearly every case of so called rising damp is just condensation - the bottom of the wall is coldest, so moisture condenses near the floor - it doesnt rise!
If you have a rotten timber frame, its because of all the modern materials used to plug the gaps and cover it - sill beams covered with cement, wattle and daub covered with cement, silicone sealant around the panels and filling holes in the wood..
NEVER use cement, tar, cement render, modern acrylic or silicone caulking on a timber frame - it will rot in front of your eyes
Never use modern acrylic or emulsion paints - they are death to old walls - they are plastic - they trap moisture and cause damp. Avoid Weathershield, Sandtex, Stormdry - any 'protective masonry coatings'.
Never use companies like Peter Cox, Timberwise, Rentokil, Kenwood unless they give you a full technical diagnosis of your problem using instruments OTHER than a damp meter, which they won't.

So called 'Rising Damp specialists', and RICS chartered building surveyors recommending damp treatment for 'Damp Walls' have caused massive, and irreparable damage to old buildings through their incompetence. Don't use them. Many of these idiots are churning out 'RICS Homebuyer Survey' reports with a standard clause in them that recommends 'Specialist Timber and Damp Survey', or 'damp survey from a member of the Property Care Association'. An entire industry has grown up on the back of it, and is thoroughly nasty and aggressive when its basis for existence is challenged. It is run by the Property Care Association - or PCA for short.

Did you know that in Holland, they don't even have damp courses? True... Even in new houses, damp proof courses are not required. They build their houses with their feet in the water, and they don't get damp walls. I teach Dutch architectural students at college, and they fall about laughing when we talk about what they call our 'Quaint English Custom' of damp courses and injection damp proofing. Sounds funny, but this is serious stuff - we are being defrauded to the tune of hundreds of millions a year, by chemical companies selling useless, fraudulent treatment.

In America they don't have a damp industry. Try walking the streets of New York. You won't see a single injection hole. When I describe what the damp industry does in this country, friends of mine in the States who are surveyors and conservation experts just howl with laughter.

Wet wall above injected damp proof course

This sopping wet wall was found in Norfolk - above a LOVELY, and completely useless injection damp course. Notice how the wall is dry beneath the injection holes, and wet above them... Best example I've ever seen of the 'Fraud Of Rising Damp'

... and the reason is.... all that lovely cement render at the bottom of a perfectly good lime plaster wall which is dry as a bone. The cement is trapping water into the wall.

The Ultimate Proof that Rising Damp Doesnt Happen!

Have a look at this photograph I took a while back. Water, running through a millrace - and the wall is dry!!

Dry brick wall with its feet in water of a millrace

.. and just to ram the point home - this is the millrace, at an hotel I stayed at. The wall above the water surface is bone dry - that's the restaurant wall you're looking at!. Damp proofing companies tell you water magically 'rises' a metre up the wall - why a metre I wonder? Anyway - this wall is sitting in water 24/7, and its bone dry - so, Mr Rising Damp man - how do you explain this?!!

Understanding your Built Environment

Restoring an old home is all about understanding the environment, and how it affects materials it's built with. By understanding this, it becomes a relatively simple task to sort out and manage problems causing damp.

Remember - it is all about 'Breathability' - such a simple ethos - allow moisture to enter and leave the building fabric without hindrance and it will never build up. Moisture is just water that has condensed - allow water to move around freely as a gas, and it will never cause a problem. Put somethng in it's way, and you will regret. Just like putting a plastic sheet on the lawn - in the morning it is wet underneath.

Temperature is a vital component. To avoid condensation, you MUST keep your home constantly heated at a gentle, low temperature. Aim to keep it at 15 degrees C. Run heating all the time, but at a low temp - radiators just warm, not blazing hot. Heating must not come on for 2 hours and go off again - it must be constantly on, but set VERY low. If you want more heat in a room, just use additional heat in that room - a wood burner, or fan heater for an hour or two. Constant heating ensures building fabric stays warm, and thus does not get cold enough for interstitial condensation to form within your walls (this is what the damp wallies call rising damp). Believe me, it doesnt cost any more to run heating like this - and many modern heating boilers are now designed to run this way.

We study the materials old houses are built with. We understand them. We work with clients to restore old homes to beautiful, warm and dry places. There is something very special about the look and feel of a lime plastered wall with clay paint - it is almost luminous in quality - very soft and welcoming. All the materials used in old homes are nice, friendly and green. By using them, not only will you FEEL good, but you will be DOING good - they are carbon friendly, and contain no toxic chemicals - lime mortars and plasters are carbon neutral, clay and linseed paints similarly - sheepswool and hemp fibre insulation are natural and nice (they are also just as good as chemical insulation), timber is a renewable resource...

We can ALWAYS find the cause of damp, whatever form it may take, and in our collective experience, we have NEVER had to drill hundreds of holes into brickwork, thereby destroying historic fabric. We NEVER inject chemicals which are supposed to stop water from 'rising' up the walls, which never did anyway.(and they are going to magically 'soak' into brick, stone, mortar and fill all the gaps... dream on!)

Avoid ANYTHING to do with the Property Care Association, or anyone claiming to be a 'Surveyor' who is using the CSRT and CSSW qualifications! They are a scam - they are not academic qualifications, and you will become another victim of the damp industry.

If a RICS Chartered Surveyor uses a 'damp meter' or 'protimeter' in a survey, refuse to accept the survey. The readings are worthless, the survey is meaningless. The surveyor does not understand the basic concepts of why moisture is present. He MUST survey to BS7913: 2013 - if he can't recite that standard, don't use him or her.

Old brick wall with existing injection damp course

Yet another classic - the surveyor recommended these people have an injection damp proof course installed. Idiot! Can you spot the existing one - rows of holes drilled into the bricks just above the tiles, plugged with cement - and the wall repointed with cement which is trapping moisture into the wall. This needs to be raked out and pointed in lime which will let the wall breathe.

A wall showing classic condensation symptoms

This is the same wall on the inside - the wallpaper is painted with a thick layer of impervious paint, and the timber skirting similarly, so nothing can release moisture. When the paper was peeled back, the wall behind was bone dry - all this is surface damage caused by condensation at the base of the wall - it does NOT need useless injection damp proof courses that dont work.

Common Examples of 'damp', and Rising Damp Solutions...

Old brick wall showing salt affected base where gypsum plaster has caused damage

View of the wall, showing the 'tide mark' where the plaster was hacked off to a metre, and replaced with impervious plaster. This then caused condensation build up, and the water caused salt damage - you can see the wall is white and fluffy towards the base...

Damp affected wall with lime plaster applied as a base coat

The same wall after the base coats of lime plaster, showing how wet the wall was - this was left for 3 months to dry out.

Damp affected wall plastered with lime, and now totally breathable

The same wall, with the lime topcoat - very little damp now showing as the wall has dried out beautifully

This is an extreme example of damp damage - in this case, the stonework of the building has been covered with cement render. This has sealed water into the structure - it has run down the face of the stone, and gone behind the render where it has built up to ridiculously high moisture levels. The only way it can escape is to evaporate out of the stone just above the render, and in so doing, it has destroyed the stone. Note that much of the stone is pointed with cement, which has exacerbated the problem. In the room inside, the walls are damp as well - moisture has penetrated through the wall and blown the plaster on the inside. All of this render needs to be removed and the stonework requires extensive repair as a result.

wet brickwork above a useless injection damp course - above engineering bricks!

The lower course of dark bricks here are Engineering Brick. They are impervious and damp cant get through them. A great Victorian damp course, properly installed. ABOVE them is an injected course, and the wall above is sopping wet. All these holes are doing is admitting water into the wall - a useless exercise

useless injected damp course above blue engineering bricks

A wet wall above injection holes, which is dry below them. A row of perfectly good blue engineering bricks acts as damp course - the injection is useless, and traps water in the wall

All about Condensation and how it relates to damp in old walls...

First - you need to understand there is no such thing as 'Rising Damp'

'Rising damp' usually shows itself as damp patches towards the bottom of a wall, in corners, at the bottom of chimneys, or as plaster falling off, or sounding hollow. Paintwork often goes flaky and powdery (damp??!) Building Surveyors or Timber and Damp Surveyors say its damp, because their silly little meter gives a high reading. This dampness reading is completely misleading - its NOT recording moisture. The reading can be high because of salts which have been drawn into the wall by the moisture. It only records conductivity, not dampness in whatever it is pushed onto - in most cases about a millimetre into the plaster on the surface of your wall. Salts are highly conductive, so even if the wall is dry, the meter will show a high reading. The surface of walls are often wet - covered in cold water that has condensed there. I can almost guarantee the wall underneath will be bone dry.

Rising Damp is a figment of building surveyors imagination - it doesn't exist!

The worst cases of seriously wet walls that we have to deal with are caused by the wall being encased in cement - external cement render, and internal 'damp proofing' plasters and renders underneath gypsum plaster. This combination is certain death to a stone or solid brick wall, and we have often removed internal plaster in cases like this to reveal crumbling brick and stone which you can poke a finger through. Left to dry out, with the offending render and plaster removed, the stone hardens and the wall dries out on its own.

Don't trust surveyors meter readings!

We often check surveyors meter readings by drilling a hole into the wall behind the plaster. We take a sample of the actual brickwork or stone - and not surprisingly when we do a proper test on the powder from the drillhole, its bone dry.

We also now have very sensitive and sophisticated equipment which we take on our surveys - this measures the relative humidity of the air in your house, the temperature, and 'dew point' - ie, the temperature at which condensation starts to take place. We measure the temperature of the walls themselves and relate this to the dew point, so you can see for yourself exactly where the problem starts, and why.

There are 3 standards which all state quite clearly that 'damp' meters can't be used to diagnose damp. If a surveyor uses a 'damp' or resistance meter and comes up with a diagnosis, or recommendation based on using one, you need to insist that they refer to these standards - BS5250 - code for the control of condensation, BS6576 - code for the installation of damp proofing and BS 7913 - conservation of historic buildings.

I find it hilarious that the Property Care Association have a 'code of practise' which is a direct crib of BS 6576, but it very conveniently omits paragraph 4 of the real code of practise, which states that damp meters cannot be used to diagnose damp - that chemical methods need to be used.

To read all about damp meters - check this out: Ping Prong meters - Guilty of Fraud

The 'Damp' is only surface deep - which makes sense. Humans breathe - when we do, moisture loads the air in the room, and condenses at the coldest spot - the bottom of the wall. That moisture is concentrated by things that retain it - plastic (acrylic paints, wallpaper, that lovely magnolia emulsion you just put on, ) or gypsum plaster, waterproof plasters, anything with cement in it... and the only way it can escape is to blow the plaster or bubble the paint.

Cement Render is Certain Death to an old house!

The same problem occurs with cement renders. There was a mistaken belief after the war (and there still is!) that damp houses were caused by water getting in through the outside walls - this rarely happens. That belief resulted in houses being covered with thick coats of cement render - which traps moisture in the fabric of the walls, and causes massive build up - which then blows out into the internal walls. The solution is to remove render and let the walls dry out. If brickwork is damaged and needs repair or replacement, it should be done with lime mortar. If it is proposed to re-render, you must always use lime render, which can breathe freely, and allows trapped moisture to escape.

Government grants to insulate - the most common cause of damp

Incredibly, one of the biggest causes of damp problems in homes nowadays is the push by the Government to insulate homes. I do dozens of surveys in which the complaint is mildew, mould, water running down walls and windows. When asked when the problem started, the answer is always the same - 'We had a grant to get insulation installed - it was after the insulation went in'. Insulation traps heat. Heat = warm air = more water held in the air as humidity. When all this humid air finds a cold wall (you insulated the roof, right? You didn't make the walls warmer... ) it condenses as mould, water, mildew on clothes and so on. Read the humidity pages to understand more about the problem... the solution - better ventilation and humidity extraction.

Common causes of damp...

Insulation
Heating on/off - must be constantly ON, but low temp = 15 degrees C
Avoid your house getting warm, then cold
Modern paints
Cement render
Gypsum plaster
Ground levels outside higher than inside
Broken guttering or missing downpipes
Vegetation growing near the wall
Trees creating shade and moist air near a wall
Lack of ventilation - double glazing, no vents
Blocked chimneys - fireplace blocked up, no vents
Furniture against walls creating cold, damp areas

Building Surveys... for the 'Timber and Damp' reports that the idiot surveyors always demand.

I need to make this section clear - if you have already had a 'building survey', and been told by the 'RICS Chartered Surveyor' that you need a timber and damp survey, the following information refers. If you are looking for a full Building Survey, please refer to the building survey pages directly..

We inspect and prepare a damp survey and report on an old building, together with recommendations and solutions to any problems found. We will NEVER suggest injection damp proofing. If you are considering buying a property, contact us to arrange a survey before you commit to buy - our report can estimate how much money you may need to spend to bring it up to scratch - and give you more confidence in your purchase.

We travel all over the country. We can examine the entire house and come up with suggestions or solutions for other related problems - we are experienced in all aspects of building conservation.

Remember: 99% of so called qualified building surveyors DO NOT understand the way old houses work. They are beautifully qualified to tell you how a modern house works, but haven't a clue what to do with the sort of problems you see on these pages. If in doubt - get the survey - but when they recommend injection damp proofing, shoot them, throw them out, report them to the Building Society - anything - but get rid of them!!! Their report isnt worth the paper it's written on.

Our costs are typically around £950 plus travelling costs for the survey. This includes a report which is usually sufficient for most purposes. We spend the day on site with you, examining a potential purchase, explaining any problems we find, and how to overcome them, with estimated costs. This gives a clear picture of what you need to budget for if you are buying a property. In some recent cases, it has meant that the property was not worth buying.

On the other hand, buyers have used our reports to negotiate a discount to the purchase price which will cover the cost of work to be done - this has exceeded £20,000.

Additional costs are charged at a day rate for report writing, depending on the detail required - we can draw up plans and Listed Building Consent applications. If you doubt the value of this approach - Contact your local Conservation Officer, who works for the Council.

More about those 'Damp Meters' ...

Your silly surveyors meter - with the two little prongs on it that's like a mini cattle prod - is what we call a resistive moisture meter. Its designed to measure moisture in wood - ok - get that.... Wood - Timber - Bits of Trees.... It was NOT designed to measure moisture in stone, or brick, or plaster...

There are 3 separate British Standards which state that 'damp' meters or resistance meters are unsuitable for measuring damp. If you get a survey from ANYONE - whether a RICS surveyor or a con artist from the PCA - if they use a 'damp' meter - you must immediately, and clearly state that these standards say a damp meter cannot be used, and how have they diagnosed damp:

BS 6576 - Code of practise for installation of damp courses - the PCA bible that they use to convince you a damp course is needed. It clearly states that you can't use a 'damp' meter to diagnose damp.

BS 5250 states the following, on page 19 of the standard:

B 8: Measurement of dampness:
Accurate measurements of the moisture content of brick or mortar cannot be obtained by the use of electrical moisture meters because the presence of salts increases the electrical conductance of the water, giving falsely high readings. Gravimetric methods carried out on samples taken from the fabric give the most reliable results. The use of chemical absorption type moisture meters will give a result in a short space of time and be almost as reliable.

Ping Prong meters - Guilty of Fraud

The moisture content of wood is very predictable - its similar in most varieties of wood, whereas stone and brick are incredibly variable in their water content and resistivity. Resistivity - electrical resistance. Its hard for electricity to travel through wood, even when its wet. Wood is a really good insulator. The meter is calibrated for this.

Stone is the opposite - wet stone carries electricity very well thanks, as does wet brickwork. Old lime plaster thats made with ash does as well - carbon is a very good conductor.. That foil backed plasterboard does pretty well when they stick the cattle prod into it - goes off the scale! Victorian paints are full of metal oxides. So... whenever your jolly Building Surveyor sticks his little prongs into the wall, its odds-on that the little red light will go off the scale. He'll gleefully announce you have rising damp, penetrating damp, and a host of other problems that can only be resolved with the application of a lot of money, and re-plastering by his recommended 'Damp Contractor' buddy, who will squirt chemicals, and generally make a mess.

There are other pieces of equipment that tell us more about moisture in walls. They include Carbide Meters, and the kit that we use - the Thermo-Hygrometer. You get much more accurate readings which tell you a lot more about the problem. There is still a lot to be said though, for personal knowledge. A wet wall can still be very little problem if the reason it is wet is properly diagnosed. Diagnosing Damp is the key. Once we know the root cause, we can sort out a solution. As you can see on these pages - the root cause is almost always NOT rising damp - its a host of other things which in a lot of cases, you yourself can control.

A word about qualifications...

Look at the letters after your 'Timber and Damp Specialists' report. Research the qualifications, (Try investigating what you have to do to get CSRT or CSSW after your name - its a joke!) and see what they mean.. Look at the syllabus - its freely available on the internet.. mostly about injection damp proofing chemicals and how to use them.. These aren't qualifications - they are about giving a veneer of respectability to people trained to commit fraud. Full academic qualifications take years to learn and acquire - these take a 2 day course with a tick box 'exam' which is mainly concerned with which chemical you inject and which you spray.. Tragic, when you don't need any chemicals in the first place. All Peter Cox damp reports have pages of 'qualifications' and 'guarantees' to try and justify their respectability. It's all a con.

More importantly, research the 'Organisation' that homebuyer surveys almost always recommend you use. The Property Care Association. Have a look at the members, the Directors - who they are, what they are - people making a very good living out of selling damp proofing chemicals, with no desire to find a solution that doesn't involve them selling you snake oil. Do some research into the Property Care Association. Look carefully - the deeper you dig, the more shocked you will be.

RICS Joint Dampness Methodology Statement

The Fraud of Rising Damp

Do some research on the array of services offered by damp proofing companies to stop 'rising damp'. Investigate their claims, and decide for yourself whether it makes sense! They'll probably recommend a water based chemical be injected - um... aren't we supposed to be getting rid of water? Ask to read the wording of their 'Insurance Backed Guarantees' sold by GPI (Guarantee Protection Insurance Ltd which is owned by the same people that own the PCA) - ask them whether they cover you for condensation damage in their guarantees - That'll send them screaming for the door... The only reason they offer these so called guarantees is that they make a lot of money selling them - notice that you have to pay extra for them... That's their commission... If you ever claim on one, they say "Yep - we cured the rising damp - and NO - this is now condensation, and its not covered"

Do you believe in Father Christmas?? When you get a survey from a 'Specialist timber and damp surveyor (who doesnt charge for the survey!!)', the surveyor is a commission salesman. Remember the old saying - you dont get owt for nowt. His sole purpose in life is to sell you timber treatment, for which he gets about 25% commission for a load of useless chemicals, and replastering, for which he gets about 20%, and injecting, for which he gets about 15%. Because so many people are brainwashed into believing this rubbish, he gets a steady income from his fraudulent sales, and the chemical companies make millions in profits every year..

Don't forget to consider the hundreds of holes they are going to drill into your wall - using a hammer drill which will smash the brickwork to pieces, fracturing both brick and stone irreparably, and weakening the base of the wall. Note how they never mention condensation, and often talk about tanking - why are they sealing more water into the structure?

You are going to take a supposedly wet wall, inject a water based chemical, and its going to dry out as a result....

Did they talk about 'bridging' the damp course? You Bet! The Dutch, who build their houses with their feet in the water DO NOT HAVE DAMP COURSES!! The Dutch say rising damp does not exist.!!!

Did they talk about damp Rising? You Bet!

Did they talk about sorting out the reason the water is there in the first place? OF COURSE NOT!!! - If they did that, they'd never work again....!!!

NEVER put anything impervious like gypsum plaster against a solid old brick or stone wall!!

Spalling (breaking up and splitting) of masonry and Efflorescence (those white fluffy bits you see on the wall)...

These are caused by soluble salts - which can either be from mortar, brick or stonework, or outside sources, such as groundwater penetration or pollution. Soot in chimneys is a great example. Burn coal: at first you get ammonia - nitrates.. Then as it burns, sulphur dioxide - which reacts with water in the air to form sulphuric acid - so now you have an unholy chemical cocktail of calcium and magnesium sulphates and nitrates. These settle in the chimney.. When temperature and humidity in the environment around the wall change, salts will either be drawn out of the wall, or when they are present in concentration, they can attract water (this is called deliquescence, or hygroscopicity - like when the salt in your salt shaker gets wet). Once this starts, you don't even need any more water - the salts attack the brick or stone and start to break it up - especially if the humidity is over 10 grams per cubic metre. A dry house is usually around 7 g/m3. You often see spalling on outside walls near streets, where acid fumes from cars attack the masonry around the height of the exhaust - this is the sulphur dioxide and nitrogen oxides in the exhaust hitting a wet wall, and forming sulphuric and nitric acid, which reacts with the material of the wall and forms salts...Once spalling starts, it is often made worse by the action of rain and frost.

Drying out wet or damp walls in an old house

Once a wall is wet, it can take a long time to dry out. There is plenty of research out there which tells us how long it will take - the process depends on how warm the air around the wall is, how dry that air is and so on - but as a rule, if your wall is a metre thick (common in old stone built houses) it can take a year for each inch to dry out properly - so working from both sides - you'll dry two inches of wall a year. This all assumes you have taken EVERYTHING off the wall - like plaster, cement render, wallpaper, paint and so on. The wall will not dry out if these things are present. Of course, the first year you'll dry more of the wall than the second year, and so on - the rate of loss of water reduces with time. If you buy an old house with a damaged roof for example and want to restore it, remember that any walls that have had water running down them from roof leaks may take over a year or more to start to dry - so you can't plaster them for a long time. If you try to plaster a damp wall, the plaster will soon fail and flake off.

And to measure the humidity in your home....

... You need one of these magic gadgets. Keep it handy, move from room to room. If you see humidity over 55%, you know you have a possible problem - not Rising Damp as the damp industry or your local PCA 'surveyor' will tell you - but condensation. Press the button, and it displays Dew Point - the temperature that building fabric needs to be for condensation to start. Armed with this, you will start to inform yourself about where and why damp may be occurring. If you have questions for us about damp problems, we need to know what levels of moisture are in the house - this is what you need.

This particular model is new - it records temp, rh, and more importantly dew point:

There is a cheaper version that will sit on your table - but it doesnt calculate dew point, which is that magic temperature we need to know about to see where condensation might be starting within your walls:

If you have one of these, we still need to download a little humidity calculator online, to convert temp/rh into absolute, and dew point. They're really good little bits of kit though, and make you aware of whether the air in your house is too damp.

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About Us

The Heritage House brand is Petes brainchild. He lives in a beautiful old farmhouse in Shropshire He's worked all over the world on old buildings, and has a strong background in geochemistry. He is passionate about ensuring the 'Rising Damp' myth is firmly buried. Pete has an all consuming project to re-open a Victorian lead mine in the Northern Pennines - digging out and exploring miles of abandoned tunnels in the search for crystal lined cavities...

This website is for information only. If you want or need a building survey, a damp survey or advice, you need to follow the links to our sister company Heritage House Surveys.