Sandstone wall letting in damp!

[vinyldude1210]

Our house was built circa 1774 and we've a gable wall constructed of sandstone. We've noticed the inside wall is damp, even wet from the ground up, to a couple of feet! We've bought a £100 Delonghi dehumidifier to help with the problem. We've had someone round from a damp and timber company (that had done previous DPC work on the building in 1992 and re-injection in February 2007). He said the wall would need rendering to prevent the ingress of moisture and that this would solve the problem, but we'd have to wait until next May/June for the wall to "dry" out before this could be carried out. Is this right? We're thinking of getting a second opinion. Who would you advise? Any other questions/help would be very much appreciated.

 

[Tom]

Hi and welcome to the forum!

First of all, have a look around the site. There's an enormous amount of information regarding your particular query. The work done previously by this company will not be helping your property but, to give you a more thorough answer, can you tell us the following;

Construction of the wall
Thickness of the wall
Is the wall plastered / rendered? If so, with what?
Ventilation in the room/s affected
Heating in the room/s
Is the house lived in? If not, how long has it been empty?
Internal floor construction
Level of external ground
Exactly what work was done by the company

There are other things that will be useful and someone with more experience than me will be along soon but the above will give them something to go on.

Jaqy

 

[MdB]

Have a read of the damp FAQ as well.

 

[vinyldude1210]

Hi and welcome to the forum!

First of all, have a look around the site. There's an enormous amount of information regarding your particular query. The work done previously by this company will not be helping your property but, to give you a more thorough answer, can you tell us the following;

Construction of the wall
Thickness of the wall
Is the wall plastered / rendered? If so, with what?
Ventilation in the room/s affected
Heating in the room/s
Is the house lived in? If not, how long has it been empty?
Internal floor construction
Level of external ground
Exactly what work was done by the company

There are other things that will be useful and someone with more experience than me will be along soon but the above will give them something to go on.

Jaqy

Hi there, thanks for the answer. not sure I can answer all the questions totally as I'm new to all this but I'll give it a go!

As i said the gable wall is made of sandstone which is 500mm thick. Not sure on the correct terminology but the wall has had some work done fairly recently in that they've re-done the mortar between each stone. the guy who was round the other day said it looked like it hadn't been done properly in that they hadn't removed the old mortar properly before re-applying it. At the top 3/4 of the wall, the stones and mortar are all intact but the further down the wall you get, the more the sandstone and mortar between the stones have eroded. there are salt deposits on the lower portion of the wall also.

that gable wall faces directly onto the road and has no protection from prevailing winds, rain etc. it's east facing. It meets the pavement directly, i.e. as people walk past on the pavement, they can touch our outside gable wall. The road also slopes down towards our house so any surface water etc will probably get splashed up on our wall if its' very wet. it is a very busy road also.

The floor inside the house at that side is slightly higher than the pavement. The area where the damp inside is worst is at the bottom of the stairs where there's no heating. This area is also next to the kitchen and we were told to shut the kitchen door when we're cooking. We're going to get an extractor fan in the kitchen soon when our handyman comes back from his holiday. The house is inhabited permanently. We have central heating which we just tend to have on in the evenings. We also have a proper fire in the lounge whose inside wall also corresponds to the problematic gable wall. Obviously the damp's not as bad in here though as it's warmer.

I think the house is reasonably well ventilated in that it's very bloody draughty (!!) but obviously we don't tend to have windows open at this time of year. our dehumidifier is soaking up about 2l of water a day at the moment!

I have no idea about internal floor construction to be completely honest. Erm, floorboards?!! Carpets in most of house, stripped floorboards in kitchen with a bit of a draught coming up from underneath.

The previous company injected a chemical damp proof course in 1992 and re-injected in Feb 2007.

The man from the company offered to re-inject again under the guarantee but said it wouldn't help. he said the entire gable wall need to be re-rendered but that we should only have it done next summer once the wall has dried out so we don't just trap all the moisture in. Naturally we're concerned that we don't want to do something that just traps moisture in and leaves us worse off than we are now with a chronic damp problem. And as having the work done will cost around £5-6k, we don't want to have it done if we don't have to. Also the gable wall is slowly being eroded so I think we do have to do something to stop it eroding even further, so it's not just a damp issue that we have. But also the damp and mould that's been growing in the house, apart from making my clothes mouldy, has been making me ill. i've had sinusitis and a chest infection as a result of all this.

But we still love the house and hate new builds!!!

We're very grateful for any advice. Will try and put some pics up later, got some doors to sand now!

 

[Tom]

Hi again

You've given a very substantial reply, which will help a lot when someone more experienced than me comes along. In particular, my comments are as follows;

As i said the gable wall is made of sandstone which is 500mm thick. Not sure on the correct terminology but the wall has had some work done fairly recently in that they've re-done the mortar between each stone. the guy who was round the other day said it looked like it hadn't been done properly in that they hadn't removed the old mortar properly before re-applying it. At the top 3/4 of the wall, the stones and mortar are all intact but the further down the wall you get, the more the sandstone and mortar between the stones have eroded. there are salt deposits on the lower portion of the wall also.

What type of mortar was replaced? Gypsum (modern mortar) or Lime (Old-fashioned type)? And what did they replace it with? Has the wall inside eroded, or is the erosion on the outside...or both? Was the house ever rendered? If so, do you know what with?

that gable wall faces directly onto the road and has no protection from prevailing winds, rain etc. it's east facing. It meets the pavement directly, i.e. as people walk past on the pavement, they can touch our outside gable wall. The road also slopes down towards our house so any surface water etc will probably get splashed up on our wall if its' very wet. it is a very busy road also.

The fact that surface water is being splashed up, and running directly to, your wall will not be helping at all. Is there a pavement outside you house or just the road? If there's a pavement, it might be worth having a word with Highways to see if they could slope the pavement away from your house, so the water runs into the gutter.

The floor inside the house at that side is slightly higher than the pavement. The area where the damp inside is worst is at the bottom of the stairs where there's no heating. This area is also next to the kitchen and we were told to shut the kitchen door when we're cooking. We're going to get an extractor fan in the kitchen soon when our handyman comes back from his holiday. The house is inhabited permanently. We have central heating which we just tend to have on in the evenings. We also have a proper fire in the lounge whose inside wall also corresponds to the problematic gable wall. Obviously the damp's not as bad in here though as it's warmer.

A cold wall and warm, moist air from the kitchen won't be helping. The moisture in the air from the kitchen will just condense on the cold wall. The extractor fan will help a great dealwith this.

I think the house is reasonably well ventilated in that it's very bloody draughty (!!) but obviously we don't tend to have windows open at this time of year. our dehumidifier is soaking up about 2l of water a day at the moment!

Your house shouldn't be too draughty but you do need some draughts for ventilation. If too much air gets inside, your dehumidifier is working way too much at your expense.

I have no idea about internal floor construction to be completely honest. Erm, floorboards?!! Carpets in most of house, stripped floorboards in kitchen with a bit of a draught coming up from underneath.

You need to find out what the floor construction is really. If it's floorboards, you should have air vents and these could be blocked which won't be helping at all. If the floors are concrete, this again could be making things worse.

The previous company injected a chemical damp proof course in 1992 and re-injected in Feb 2007.

I suspect that all this work has done nothing to help the property at all and might well be the cause of some of the problems you're having.

The man from the company offered to re-inject again under the guarantee but said it wouldn't help. he said the entire gable wall need to be re-rendered but that we should only have it done next summer once the wall has dried out so we don't just trap all the moisture in. Naturally we're concerned that we don't want to do something that just traps moisture in and leaves us worse off than we are now with a chronic damp problem. And as having the work done will cost around £5-6k, we don't want to have it done if we don't have to. Also the gable wall is slowly being eroded so I think we do have to do something to stop it eroding even further, so it's not just a damp issue that we have. But also the damp and mould that's been growing in the house, apart from making my clothes mouldy, has been making me ill. i've had sinusitis and a chest infection as a result of all this.

Don't do anything else until you work out what's causing the problems. Dealing with damp is often quite complex (as you're about to learn!) and needs to be done in the correct way that suits older properties. It won't be a quick fix but the results will be far better than using quick fix modern treatments.

But we still love the house and hate new builds!!!

Well, you've come to the right place!! Many of us here have had very similar problems and can help you out.

We're very grateful for any advice. Will try and put some pics up later, got some doors to sand now!

Pictures would help a lot. Enjoy sanding your doors! Someone will be along very soon to help you further but weekend is normally a slowish time on here as people are working on their houses. Bear with us!!

Jaqy

 

[MdB]

Two years ago (almost to the day) I started posting about our damp sandstone wall - thread here (images don't work). After working out what the problem was (lots of layers of stuff on the inside stopping the moisture escaping) and sorting (by removing all the layers) the damp has now gone, hopefully for good.

Back then, I wasn't an expert. Now, I am still not an expert but I have read up an awful lot so know more than I did. You will find lots of conflicting advise on what causes damp and the best cures. Mainly this is builders on one side and people who know about old properties on the other. I am very much on the side that a lot of what builders do, might help in the short term (10 years say) but makes things worse in the longer term.

General principles are that modern materials (cement, concrete etc) are generally strong, don't get weaker when wet and are generally water resistant. Modern wall construction with a cavity also allows the outer layer to get wet without affecting the inner layer.

Older materials (stone, mud, lime etc) are not as strong, can get weaker when wet and can soak water up like a sponge. Walls are generally solid so if the outside layer of the wall gets wet, this will travel all the way through the wall.

You may think that the best way to keep an old wall dry is to stop moisture getting into it in the first place. This is important, but far more important is to allow a way for the moisture that does get in, to get out again. A modern wall with good foundations and made from cement and concrete will stay as one solid lump and can be kept pretty waterproof. An old wall made from stone, mud, lime and probably a whole lot of other things with no foundations will move all over the place during the year as moisture levels change so there will always be cracks and ways for water to get in. It is therefore important to allow this water to escape.

If the moisture levels in the wall get too high, damp patches appear, the wall loses its ability to conserve heat so it cools and collects more condensation - which makes the wall damper.

Some sources of moisture are: Rain on the outside of the wall, ground water levels, people living inside of the building, faults - such as leaking gutters, leaking pipes etc.

Faults etc need to be identified and fixed. Outside ground levels need to be dropped below inside floor levels.

People need to be thrown out of the building... Ok so maybe that isn't an option. People produce a lot of moisture with the kitchen and bathrooms being the main sources. This moisture needs to be able to get out of the building so ventilation is very important, especially in the kitchen and bathroom. It doesn't make for a warm house though which is why people don't like the idea of opening windows etc.

Rain on the walls can be dealt in two ways, you can either try and stop the water soaking in or you can let it in and then let it out straight away.

A waterproof finish (such as a cement render, layers of modern paint or some waterproof coating) will do a good job of stopping the vast majority of rain from getting into your wall, especially for the first few years. However, an old wall will move and crack allowing water in. Also, a small amount of water getting in, is a problem if once it is in it can't get back out again. This way the moisture levels will gradually rise every time it rains. The very surface that stops the majority of the water from getting in also stops the remainder from getting out again.

The alternative method is to allow some of the rain water to get into the wall but also to let it evaporate away again just as easily. Porous stone will do this naturally as will lime mortar. This may seem a strange way of keeping dry but remember in the UK the number of hours it rains is small compared to the hours it doesn't rain so there is more evaporation time than there is getting wet time. (I'm finding that hard to believe at the moment though...) The process of letting the water in and out is known as the house breathing.

I'm rambling so lets get back to the subject at hand...

You imply that your house has exposed sandstone blocks on the outside together with some mortar which has been recently repointed. (the stuff between the stones on the outside is known as the pointing.) As it has been done recently, it is likely to be have been done is cement. Cement is fairly waterproof so will stop any moisture behind it from getting out (stops the wall breathing). It is also stronger than the stone so won't move when the stone moves about so will crack allowing in water. Builders love it, we don't. Ideally, the pointing wants to be done in lime which will allow the moisture out and will to a certain extent move with the wall.

Has the wall been painted? If so it is likely to be a modern emulsion - i.e. it is a layer of plastic on the wall stopping the moisture from escaping. Ideally, this needs to be removed and replaced with a breathable paint. This means a properly breathable paint such a lime wash and not one that just says breathable on the can.

I have said ideally twice in the above as neither of these problems are easy to fix and require a lot a labour. I have both these problems and haven't done either yet. They are on the to do list and quite a long way down that list too.

Inside, you don't have the problem of it getting wet from rain, but you do have the same issue of moisture inside the wall getting out. Originally the wall is likely to have been rendered in lime and painted in lime wash. This is an ideal surface for an old house as it is highly breathable and allows the moisture within the wall to escape.

Unfortunately it is likely that the render has been replaced with modern gypsum as some stage and highly likely that it has been painted in some modern non breathing emulsion. Again this isn't an easy problem to fix.

What you can do as a first stage is to identify exactly which of the above problems you do have and what it is possible to do about it. Coming here and asking questions is the start of this process. You have already had people in to look at your damp problem, I would be suspicious of the damp company and any builder who is not an expert in old buildings. The person you do want to listen to is the one that SPAB recommends to you and that you have to pay to get their opinion.

 

[chuckey]

Some sandstone is very soft and is porous. I have found what look like sandstone rocks and cut them in half with blow from my spade, on examining them they are totally saturated with water. Thick walls are some times built with an inner skin and an outer skin with the core filled with rubble.
Now to your problem, if the problem is penetrating rain, then you should have damp patches at a high level. This is complicated by the "throughs", stones running from the outer skin right through the whole wall to the inside of the inner, here you tend to have horizontal patches at some random height across an outside wall. the inner rubble core will have a pile of dust, mortar and general crud which will accumalate right in the bottom of the wall. So any water drips running down the inside of the outer skin will make this pile of rubbish wet and so get the inner skin wet. Also your heating will dry out the higher reaches of living rooms , leaving the lower areas cold, so a, not drying them out and b, allowing condensation.
As the bottom blocks are eroding,, this could an indication of water saturation followed by a frost "blowing" the top surface off.
The opposite, could be the problem, after prolonged heavy rain, the grounds water table rises and with the natural suction of porous stone, the bottom stones could be saturated and the damp appear above your floor level.
The first thing to ascertain is your wall construction, are the walls solid blocks or rock and rubble? I believe, if done properly, silicone injection can work, so can you see the filled holes on the outside and inside of the walls? - ask the rep how they would have been done. If its still under guarantee, they should have all the details. If the blocks are solid, then it would take an awful long time time and a lot of silicon to damproof them them properly. I would say at least two minutes per block per linear foot. It is quite likely that the lads who did the job, just went for a quick squirt and the blocks are not truly injected, they just have a blob at their centre that is waterproof.
Floor construction, jump on them if they bounce, they are floor boards. (
put a bunch of keys in a saucer adjacent to where your jump, if they rattle its wood!), also if they are wood they should be showing some sort of distress if their ends are constantly being kept damp.
Do not render the wall, at least not for 3 years and N trys at something else, it will cause all sorts of other problems.
I would lift a floorboard or two on the gable end and see whats happening underneath and if it seems damp, scrape out the mortar on a vertical joint or two, to alow any trapped water to leak out and to provide an air bleed to help dry the wall. If after going through the mortar, you find earth, keep on going until the hole is at least the depth of the wall, or untill you hit another block (the other skin)
Make sure the pointing is all there, i.e. no bits missing and no holes then apply silicone to the whole wall, its quick cheap and non intrusive and again it can help.
Try and lower the water table around the house.
Old houses, bad builders Grrrr!
Frank

 

[vinyldude1210]

Wow, thanks so much for all the advice! We're a bit overwhelmed now so I'll try and address what you've said in order. :shock:

I'm just not sure what kind of mortar was there before and what's there now. I took some pics today. not sure if they help at all....

There's no erosion on the inside, the wall is damp/wet from the floor up to a height of around 2-3ft. As you can see there is some erosion on the outside wall, and salt deposits. As you can see, the pavement and our gable wall meet. The road slopes down to our side of the street and there's a highway drain a few feet away from our house. Good suggestion re asking the highways agency, or maybe the local council?

really not sure about the floors. We think (!) that it's floorboards in the kitchen and bottom of stairs but concrete here in the lounge, which is also on the gable wall side. Lounge and bottom of stairs are carpeted, kitchen has bare floarboards. Reason being there's a cellar under the lounge with a vaulted ceiling. We were told that you'd always have stone or concrete on top of that. the cellar may be contributing as it's very damp down there, it's below ground level and seems to have a natural spring in one corner! There's a small window in the cellar which we've started keeping open all year round to try and create more ventilation.

Only got as far as buying the sandpaper and varnish today!...

MDB, thanks for the post! What you're saying re letting the walls breathe and letting water in and out again makes a lot of sense. We're going to have extractor fans fitted asap and have got the dehumidifier on permanently! What would your opinion be of getting trickle vents fitted to the windows? Though the house is quite draughty, I'm not sure if that's enough.

I don't think that gable wall has been painted but the opposite one has been covered in bitumen (!). The bitumened side can't be seen from the street and backs out onto a private access road. So wondering what you're saying means regarding that? Should also say, since you mention movement, that this pesky gable wall in question has moved in the past and has been strapped!

What's SPAB?!

How do we work out if the wall's made of solid stone or not? We think it is but can't be sure. We think the house was built in 1774 if that helps. I've attached more pics of the house, hope they help. But also we're quite proud of our baby and like to show it to people!

Thanks again for all the advice!

 

[Gervase]

Ah, that's modern cement mortar, and it's already damaging the stonework. As time goes by the stone will spall and erode even more, leaving you with bands of hard mortar standing proud of the wall. The picture is almost a text-book example of what not to do with soft stone! It's also been applied very badly.
I know it's probably not what you want to hear, but to preserve the stonework all that mortar needs to be carefully removed (not with an angle-grinder, which is what a lot of builders will use) and replaced with a lime pointing mortar.
Much of the back of the house looks fine - no signs of cement there, but the sides need to be sorted, particularly at the lower levels, where it's clear that the worst of the cement pointing has been done. I'm afraid it looks as though the damp-proofing company has done an absolutely terrible job there, making a bad job much worse.

 

[chuckey]

To add to what Grvasse said. Buy a stainless steel knife from an Oxfam shop for 10p and a very thin wood chisel from a cheapo source (market trader etc.) for about £1. Now try and get under the mortar and flake it of, it looks as though a goodly portion will come off easily. You are allowed to use a small hammer on the end of the knife so it is really a lightweight chisel. The water is not coming through the pointing on the back of the house- right?, so the cement mortar is just a trap for the entry of water.
Now your silly con injection is just that. Imagine one of those holes, when silicone is pumped into it, once the silicone hits the relatively soft lime, it will flow into the lime so the protected area is at the most a tube exactly the radius from the centre of the hole to where the tube runs into lime work. In the worse case if there is a flaw in the block so there is a crack between the hole and the lime, all the silicone goes straight through the flaw into the lime and the block remains unprotected. rather akin to water down a plug hole.
Frank

 

[Nemesis]

Struth - that's one of the worst pointing jobs I have ever seen

SPAB:

http://www.spab.org.uk


http://www.spab.org.uk/html/advice/technical-qas/technical-qa-11-repointing/


http://www.newforest.gov.uk/media/adobe/pointing.pdf


http://www.historic-scotland.gov.uk/index/learning/publications/publicationsresultsdetail.htm?id=49164a7c32


http://www.historic-scotland.gov.uk/index/learning/publications/publicationsresultsdetail.htm?id=49164a7f11

 

[vinyldude1210]

Thanks again for all the advice. So basically that wall's been repointed by a total cowboy? Great stuff! i've emailed the people we bought the house from to ask when it was done and by whom. Don't know if that'll help at all but I suppose the more info we have the better.

So do you think that we need to remove all the cement mortar from the whole wall and replace it with lime mortar or just do the bits that have eroded? Presumably we have till spring/summer to do this?

Is there anything we can do about the DPC? i.e. can it be removed or is the damage just done now?

Do we need to worry about the stones that have been eroded already? if so, what can we do about them?

We're more than happy to pay a specialist to come round and give us some proper advice. How do we go about finding one?!!

 

[Gervase]

Don't panic!
Yes, the repointing is the work of a complete cowboy, but it's not too late to do something about it.
The DPC will just be sitting there, uselessly puddled in one course of mortar, so I wouldn't worry overly about that. I don't know what the weather's like where you are, but lime mortar doesn't like frost, so repointing is best left until March. Get it done in the spring and that will go a long way to undoing the awful job that's been done.
The erosion on the stones can be fixed, but it's an expensive and fiddly process. Looking at the photographs, however, it isn't too bad as yet, so provided the cement pointing is removed before it endures yet another wet winter you should be OK.
You can find a specialist surveyor through the 'seeking specialists' section on this site, or through SPAB. It's well worth the membership if you look after an older house, as the support and advice is invaluable and can actually save you large amounts of money and grief. If you do decided to chase up the cowboys who did the job, good luck, but an informed comment from a specialist with letters after his or her name might strengthen your case.

 

[vinyldude1210]

So we need to get the cement removed asap and have the lime mortar put in next year? Is there any potential for bad things happening if there's no mortar in for a few months?

Great, I'll look on here and on SPAB to find someone good. We live in West Yorkshire and are fairly high up so the weather's not exactly what you'd call tropical! We get frosts as late as mid May and have had some frost already, and plenty of rain obviously!

The work was done before we moved in, not even sure if it was done in the tenure of the previous owners to be honest so don't think we'd get anywhere chasing that up.

I'll let you know how we get on, thanks!

 

[MdB]

Gervase is one of the experts here so listen to him more than the rest of us (especially me).

Yes, the pointing was done incorrectly with cement but this is very common. My original post mentioned builders on one side and people who know about old properties on the other. This is one of those situations. If you can find a builder who thinks putting lime pointing on the walls is a good idea then get his name as quickly as possible. Most builders just use cement and can't understand why you would want to use anything else.

Others may have better views on this than me, but I would also say that sorting the pointing out is unlikely to sort out the damp problem inside. The surface area of the pointing is small relative to the surface area of the stone so although it will make a bit of difference, it won't make a great difference and probably not enough to notice.

One idea that did occur to me was to get you to find out what sort of ground floor you have. If it is solid, is it concrete?, if it is wood, is there good ventilation into and out of the under floor cavity? It appears to be fairly common to have poor ventilation under timber floors and this problem can lead to long term damage and internal damp so is worth checking.

 

[Nemesis]

I think it would surprise how much defective pointing can allow damp to enter a wall. Under that cracked cement is lime, which has probably eroded through time. We have a single skinned section of wall behind the stove at the back of the fireplace, and it doesn't take much of a crack in the mortar (next year's job) to watch rain run in and down the wall.

Water gets in and can't easily get out, and works its way inside a solid wall. It can also drain down to the bottom, so what can be diagnosed as rising damp is in fact falling damp. Then there is splashing from traffic, as well as driving rain.

Certainly one of the first things I'd do is to remove (carefully) as much of that smeared cement as possible, and renew the lime mortar, then give it all a long time to dry. Will do some good, can do no harm, apart from maybe removing a bit of stone along with the cement. And how much better it will all look - see the front of the building, that's how it should be.

I know that this 'ribbon pointing' has become the norm in areas round west Yorks, but the long term harm is going to be dreadful.