It's almost inevitable that you will find damp in an old house. Nothing lasts forever, but despite the English weather, our old buildings can, and will stand the test of time. The worst enemy of old houses is we humans - it's generally what we do to them, or fail to understand about them, that causes most of the problems and make you think you have to Damp Proof it.

In recent years, so called 'Rising Damp specialists, and building surveyors recommending damp treatment have caused massive, and in many cases, irreparable damage to old buildings through their incompetence. Don't use them.

Don't stop walls breathing!

When a wall warms up after a cool night, the air contained within its pores expands as it warms and a small proportion moves out of the wall via the connected pores. As the wall cools down again the air within contracts and air moves back into the wall from the atmosphere. And so masonry walls ‘breathe’ – out as they warm and in as they cool. Breathing occurs on a daily basis, or more frequently in periods of variable weather; breathing is shallow when there is little temperature variation and deepest when the daily range is greatest. Of course, walls don’t actually breathe in the human sense: they just sit there while changes in temperature (and air pressure) do the work, but the ‘breathing’ analogy is a convenient way of understanding frequent exchanges of air from masonry to atmosphere and back again. If the air drawn into a wall is humid and if the wall material cools below the dew point then some of the water vapour in the humid air will condense as water droplets within the pores of the masonry, though the wall will still be ‘dry’. During warmer and drier times some of this water will evaporate and leave the wall as it breathes out. And so apparently dry walls commonly 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 then the amount of water drawn into (and retained in) the wall can be sufficient to make the wall visibly damp, even in dry weather.

Anything that prevents a masonry wall from breathing will reduce its life expectancy. Coatings that are designed to seal the surface of masonry walls (and so ‘protect’ them) will 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, the damage caused by the inappropriate use of coatings can be dramatic . The coatings themselves - cement renders, gypsum plasters, plastic emulsion paints - will eventually be forced off the wall.

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. 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.

• Rising Damp is almost non-existent - it rarely occurs naturally , and it CERTAINLY doesnt move a metre up the walls as 'damp proofing' so called 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, and water which is wicked up the brick reaches the first mortar joint and evaporates. It NEVER goes beyond the first joint unless it is bridged - for example, by removing the lime mortar and replacing it with cement. It certainly doesnt go the magical metre high that every rising damp salesman will claim.
• 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
• 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 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!!

This sopping wet wall was found in Norfolk last week - 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.

.. 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?!!

Building conservation and restoration is all about understanding the built environment, and how it affects the materials which make up your home. By understanding this, it becomes a relatively simple task to sort out problems causing damp, and manage them for the long term. We can ALWAYS find the cause of damp, whatever form it may take, and I have to say that in our collective experience, we have NEVER had to drill hundreds of holes into the lower courses of brickwork, thereby destroying them. 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!)

Rising damp is a wonderful marketing tool used to sell millions of pounds worth of worthless chemicals and labour to an unsuspecting public, irreparably damaging structural brickwork in the process, and don't forget that they always want to re-plaster the walls with impermeable plaster - this just makes the problem come back in ten years or so..! Great for business if you're flogging rising damp treatments....

We have often surveyed damp houses which have had more than one set of holes drilled - some - the worst we've seen, have had three or four sets of injection damp proofing holes and chemicals injected, and they are still sopping wet. When will people, surveyors, and the mortgage companies, wake up?

Please.... DON'T be fooled into using injection damp proofing - it's a waste of money. Take note that they nearly always make you hack off the plaster to the obligatory metre high - as in the photos below, and give it a 15 year guarantee - then in 16 years, when all the plaster falls off again, its magically out of guarantee, or the company vanished into thin air..

Every damp problem has a specific cause, and it is usually easy to fix that cause - for example, faulty guttering, external ground levels too high, concrete / cement render trapping moisture on outside walls, and so on. Our survey will outline any problems, and suggest solutions, which never include injection damp proofing!

The Fraud of Rising Damp

Do some research on the huge 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?

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

Do you believe in Father Christmas ??

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?

Did they talk about 'bridging' the damp course? You Bet!

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....!!!

This is an interesting one - an old farm building with gypsum plasterboard 'dabbed' onto bare brick with gypsum cement. The dab cement has soaked up moisture in the air and is holding it - hence the lovely dabs all over the wall which are sopping wet.

Reminder - never put anything impervious like gypsum plaster against a solid old brick 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 the mortar, brick or stonework, or from outside sources, such as groundwater penetration or pollution (soot in chimneys is a great example). 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 - 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 in the 75% range. A dry house is usually around 45 to 50% range. 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 in the exhaust hitting a wet wall, and forming sulphuric 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.

Great one this... Look at the TWO sets of holes drilled above each other and shattering the brickwork. This house was sopping wet inside, all caused by condensation. I've chopped the cement render off to expose the bricks underneath. The mortar was like gooey clay, but hardened up when able to dry. The injection damp course was about as useless as a square wheel.

You can probably see that the bricks below the course are quite dry - and the wall gets wetter between the holes and above them. All that was needed here, was to take the render off! The wall is lovely and dry now we've removed all the cement render that was trapping condensation into the wall.