Damp, tried everything, what now?

[Zebra]

I'm wondering whether it might be the right time to consider more drastic measures with regard to damp, and would be grateful for any suggestions.

The original (17th/18th century?) solid brick walls of my living room are built of very soft porous brick, and there's a line of damp visible up to around 300mm. I've done all the right things so far: I've checked for faulty guttering, built a retaining wall to keep the soil away, or lowered external ground levels. I've taken the concrete slab away on the inside and dug a breathing trench which is still open. I've removed all impermeable coatings and repointed in lime. I've plastered the outside in lime.

This is the line of damp seen from the outside at the back where there is a retaining wall. It's still damp down in the gully, whereas above it is dry.


This is the line of damp seen from the outside at the front where I've lowered external ground levels.


And from the inside:


I can no longer accept that it is just taking time to dry out. The bricks are very soft and porous, so they absorb a lot of water but also dry very quickly. I absolutely saturated the wall when I plastered it, and higher up it has dried, lower down it hasn't. It gets wetter and drier with the weather. Either it's drawing the moisture up from the ground, or it's splashing against the wall, but with the same effect.

The damp is only on external walls. In areas where the house has been extended and so an original external wall with its feet directly in the soil is now internal, it's generally quite dry-ish. This still doesn't identify the cause though, because either the damp is spashing rainfall even though the ground is soft and absorbent, or it's rising up through the brick from the wetter ground outside.

So what now? After doing all this work on the house, spending so much of my time and tens of thousands of pounds, I can't really see myself just accepting having a living room with wet walls. Yes we're in a spell of wet weather but there will be wet spells again.

If injecting is out, electro-osmotic dpcs aren't considered to be up to much, what about physically cutting in a dpc? This won't help if it is splashing rainfall that's causing it.

Or what about allowing the moisture to rise up and escape outwards, but having a barrier internally? Would it be feasible to line the inside up to 500mm or so with a polythene membrane lapped into a floor membrane? What are people's experiences who've removed such a thing from an old house, does it go mouldy and nasty underneath the membrane? Or what if I were to paint the walls with a bitumen based liquid waterproofer, but over a new coat of lime mortar, so that the bitumen didn't damage the bricks? As long as the external surfaces were breathable, then any moisture which did rise up could escape outwards, and I would be dry.

I'd be grateful for any help, as I really can't see where to go next with this.

 

[JoceAndChris]

Poor Zebra, I can feel your frustration in that. I don't get your building though,there seems to be every building material you can think of thrown at it - bricks, breeze blocks, concrete? What's going on? My understanding was that where old material meets new trouble (damp) can occur.

I'd really stay away from bitumen, better to have that bit of visible damp you can deal with, with heating, and ventilation. Damp is helped by layer upon layer of limewash,on the outside and the in, this was used to consolidate the building - the limewash is a sacrificial layer to protect the building - you've not yet had a chance to put that in place.

If it's any consolation we removed thick, concretey render from the exterior of the porch because there was a damp patch in the bathroom. The stone breathed, the lime plaster and distemper on the inside breathed and the damp patch slowly dried out over winter and early spring. Now, with a wettish summer, that damp patch is partly back. The stone, where it's naked, is very porous, the rain hits it and penetrates. It needs a good few layers of lime plaster and limewash to sort it out. But we can't afford it just now, so will leave it until next year to sort it out, and not worry about it.

I don't believe that these porous houses were always dry, in fact, you only have to dip into Bronte or Dickens to read that they weren't.

 

[middi]

Zebra, if you walls are constructed from porous " soft reds" without dpc you will always experience " rising damp" to some degree. It all depends on the amount of water and moisture that is retained in the subsoil below the walls foundations. This condition will be aggravated, as one would expect, when there is more rainfall and less sunny and windy days the bricks will not only suck water from the saturated soil but will also retain moisture from rain that splashes against the walls.
There is another factor which which should be understood where soft red bricks are concerned. Soft "reds", when subjected to the numerous cycles of wet, damp, frosts, ground salts and dry periods will naturally degrade. The clay used to make up their mass varies in quality and method of construction and , to some degree, would have varied from different brick manufacturers to another with different clay constituents dependant on regional area.
In general. all " soft reds" are " breatheable, unfortunately when they start DEGRADING the tendency is to gradually revert to dust and will become a "magnet" for retaining moisture, a breakdown will occur within the brick porousity and the rate at which they should be drying out under normal circumstances.
All you have done so far is the correct thing ie- allow the evaporation process to take place by exposing the surface area of the brick face-.
If no DPC is in place, and the ground is wet, you will not stop the moisture being sucked up the walls from the ground, or the rain splashing against the bricks.
There are so many variable factors that can contribute to damp problems and yours is a perfect example why damp is so difficult to discuss and suggest solutions without a close look at the problem and , perhaps, a process of elimination ( as you are doing).
In the end one may have to accept the fact that drastical ( or lateral thinking) solution may be required to solve and eliminate the problem.
The only silver lining in your dark cloud is that it is higly unlikely you need to rebuild the house, Just serious drastic action required if you are fed up with the damp. Perhaps a bit of money spend on professional (on site) opinion is be the answer.

Middi

 

[AMc]

As far as the actual problem goes. You can rule out/in splash back onto the walls by constructing a temporary "tent" from some polythene or tarpaulin over a section that shows the problem. Leave the ends open so there is plenty of ventilation and wait for the beautiful summer weather to do it's thing. If the wall in the middle looks dry/drier after rain then you know that splash back is at least partly responsible. I'm not sure what you do next though, but it makes sense to have as much information as you can gain.

You have my complete sympathy - you've obviously been trying really hard to do the right things for the house but you haven't got there yet - I hope you're not losing heart.
There was a point in my renovation when the money had almost run out and the work was nowhere near finished and I really wanted to put a match to the whole thing and move to a modern box.
Thankfully that passed, but if you can take a break from the house entirely for a few days I would.

Good luck!

 

[Flyfisher]

As far as the actual problem goes. You can rule out/in splash back onto the walls by constructing a temporary "tent" from some polythene or tarpaulin over a section that shows the problem. Leave the ends open so there is plenty of ventilation and wait for the beautiful summer weather to do it's thing. If the wall in the middle looks dry/drier after rain then you know that splash back is at least partly responsible.

Good suggestions. I have a few areas where I've done something similar. In one place I just lent a couple of sheets of old plywood against the wall and the effect was quite dramatic. In the other place, higher up a wall and a buttress, I some treated roof battens to the wall and then stapled breathable roofing membrane across it. Again, the effect was quite dramatic and the wall is now dry to the touch.

These are only temporary fixes (hopefully!) but they do provide some valuable information about how the house is 'working' before doing anything more expensive.

 

[AMc]

Also might be worth considering a "test pit" somewhere to see what the water table is like? Obviously don't dig deep hole near the foundations

I was fortunate to discover a well during excavating my kitchen floor. While the cost of lights, casing and walkable glass was considerable, it was good to know that the water table is a good 3m below my house. It now provides a handy barometer on the likelyhood of a hosepipe ban as you can see the level change over the months.

 

[MdB]

it was good to know that the water table is a good 3m below my house

Mine on the other hand can be about 100mm below floor level on occasions. Equally useful to know though as it means I can take it into account when doing work. If you do dig a pit, make sure it is somewhere covered so it doesn't just fill from rain water.

 

[Zebra]

Joce, thanks for your advice. So limewash helps, does it? Does it help the wall to dry faster, or keep the moisture in the wall? I'm very grateful for the tip, but not quite sure how that would really help, and how much should I put on? It'd be easy to just layer it and layer it with limewash, but if limewash doesn't impede the passage of moisture, how would it affect the amount of water in the wall?
I've had a side extension demolished (I posted about it ages ago) and rebuilt in modern materials to comply with Building Regs, hence the breeze blocks etc. It will all be lime rendered to look more like the old. But the damp existed before the modern extension was there, and I don't think it's a cause.
Heating and ventilation is an issue. I don't have any windows or vents at the back of the house so don't get any through draught. Also I have no central heating, only the woodburner which I light when it's cold enough. Feltwell I think it was recommended leaving the door of the woodburner open when it's not in use to try to create some "passive stack" ventilation, but it's not really enough.
Yes perhaps Bronte and Dickens may show that these houses were often damp, but people also used to die in their forties from TB and have arthritis and rheumatism!

Middi, thanks for your explanation of how soft reds behave and how they degrade over time. Do you mean that even if they don't look damaged, they will be more absorbent now than when the house was first built? However, you don't give me much hope for a solution!
I did have a conservation architect in, someone who's studied the use of insulation on old buildings, paid him to do a detailed spec, and for the ground floor he recommended an injected dpc, bitumen based tanking system on the outside, and XPS insulation on the inside, none of which seems right to me, and so I've ignored his advice. When I questioned him on it he said yes breathability is important, but you don't really want all that moisture evaporating inside the house.
So as you say, perhaps drastic action will be required. Any ideas?!

AMC and Flyfisher, that's a good tip, I'll stand a board upright in the gully, I'll go and do that now, it's supposed to rain again this week. Thanks for your sympathy also AMC. I've not lost heart yet, I love the house, am still keen to spend as much time as I can working on it, and still have money in the bank, but am just really stumped over this issue.....!

As for the water table, it's not high at all. I have a four foot deep pit right next to the house, the rainwater pit which you were all kind enough to advise me about a while ago. It now has no bottom so the level in it will rise or fall with the water table, and it's empty. The damp in the walls therefore is either absorbed from recent rainfall in the ground before it soaks away, or is splashback.

 

[agbagb]

Ok who is going to be the first to slap my wrists for sugesting a siloxane treatment to the brick. I've found it very effective on soft and damaged brick, rain and splashes just run off and it's breathable and invisible.

I used it on the front of this house after chipping of all the render and repointing in NHL. The walls where sodden behind the render and the faces of the bricks totaly shot after I'd had the breaker on it.

It soon dried out and hasn't shown any problems for the last nearly three years.

It could well sort out the splashing problem.

 

[middi]

Personally , Zebra, If i was faced with same problem that you have I would not hesitate and would install a dpc in the base wall. It is a bit slow and laborious I know, but then I would not pay anybodyelse to do it and the materials involved would amount to less than 50 quid.
If I did as above I would seriously also contemplate re-doing the internal floors by inserting a membrane lapped into the dpc and as much underfloor insulation that I could get away with and get rid of the underfloor ventilation system. Between skip hire and materials it would cost me less than 500 quid plus my own labour. This would not hinder the look of the property, it will be warmer and damp free.
I would then guarantee that no damp will ever come up through the floor, or be sucked up the wall, for at least another thousand years.
I appreciate the fact that you may have to pay someone else to do this work for you and therefore considerally more expensive.

I would not consider half hearted repairs such as wall injection or bitumen/tar coverings, this may turn out to be a waste of time and money unless you get a 25 year written guarantee and I boubt if anybody would give you such guarantee,
Ps. lime wash will only make red brick walls look a different colour, it does not improve breatheability in soft reds. As a matter of fact, anything one applies to the exterior of well pointed soft red bricks does very little or nothing at all ( worse probably) to improve the breatheable factor

As how you should proceed with you problem it is a case for you to decide, if you want to get rid of the damp for good, half hearted attempts may not cure the problem but may cause your heart to fail :wink:

Still, you also have to appreciate it is my view to a solution for a problem that I have only read about on a forum and may not necessarely be the right one for your situation.

Middi

 

[Gareth Hughes]

Ok who is going to be the first to slap my wrists for sugesting a siloxane treatment to the brick. I've found it very effective on soft and damaged brick, rain and splashes just run off and it's breathable and invisible.

I used it on the front of this house after chipping of all the render and repointing in NHL. The walls where sodden behind the render and the faces of the bricks totaly shot after I'd had the breaker on it.

It soon dried out and hasn't shown any problems for the last nearly three years.

It could well sort out the splashing problem.

Me, I'll slap your wrists. I appreciate that once a soft brick house has been hard cement rendered, it can never go back to being exposed brick, but ooh, nearly three years!? gosh, that's almost as old as my niece, and she hasn't needed a remedial coating in that time either...

 

[rebeccac]

Yes its so frustrating when we follow all the 'rules' and then still find these areas of damp that just never seem to go away.

We are currently living in a house owned by the National Trust which is build from slate stone and is about 200 years old.Unfortunately just about everything that could have been done to create damp problems has been done including a horrible cement peeble dash applied in the 1960's and a damp proof membrane under the foor which just traps water underneath making the room smell musty nearly all of the time.

When we bought a similar size stone house in Italy we knew that we would need to do the exact oppersit to what the National Trust had done in Cornwall.After 5 years we have solved about 90% of the damp problems with just the kitchen floor to tackle.We get damp bricks with salts and lots of damp in the air even with doors and windows open in June! Our solution of lifting the floor and relaying on gravel/sand and digging drains at the bases of the 2 'problem' walls to take damp away is going to be tried out later in the year - we hope it will work!

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[middi]

I don't understand Rebecca, if the Impermeable underfloor membrane is lapped into a dpc in the walls how can you get damp and smells coming up from the ground or damp and smells coming up the walls. It is impossible.
Either the job was half heartedly done and incorrect or the source of the damp is from anywhere else apart from the ground.
I also have a house in Italy ( olive grove and all that) built out of tufa stone which is very porous , no dpc inserted and a permanent " salty " damp line appears within the inner walls, up to 40 cm high, especially in winter. In the spring I just brush off the salty deposits from the lower part of the inner walls, the windows are left open, and the walls will be bone dry untill the oncoming of winter. If I get fed up with the damp I will insert a dpc in the walls. I know what it needs, but cannot be bothered with it ( mainly because I only spend few weeks a year in it.
This house is built on flat ground on an undulating hill top, my father's house which is of exactly same construction but a couple of hundred yards away on the down slope of the same hill has no damp whatsoever. It just proves how damp can behave on homes built the same way but in a slightly different position where ground levels, surface water dissipation and water tables are slightly different.

Middi

 

[JoceAndChris]

Joce, thanks for your advice. So limewash helps, does it? Does it help the wall to dry faster, or keep the moisture in the wall? I'm very grateful for the tip, but not quite sure how that would really help, and how much should I put on? It'd be easy to just layer it and layer it with limewash, but if limewash doesn't impede the passage of moisture, how would it affect the amount of water in the wall?

I apologise for being about as clear as mud. My meaning was that if you house were dry, once it's dry, limewash and lime render will help to prevent the moisture and weather getting in - as Middi says although they are breathable materials they are more of a barrier than having a naked wall. I have a lot of suffering naked walls, looking forward to a nice coating in lime.

But no, limewash in itself won't draw out moisture or anything like that, it's no quick solution for the drying out process your house has got to go through now. What it does do, though, is show up damp patches very effectively. I didn't even realise I had a damp bathroom wall until removing the modern emulsion and painting on distemper. But I think the idea of putting up a waterproof sheet and seeing what's going on much better than anything more permanent at present.

And I also think you might be falling into the trap of judging a half-done house during an early summer, that, I read, has received the equivalent of an entire winter's rainfall in two months.

And I'd certainly always defer to Middi's expertise.

 

[JoceAndChris]

Ok who is going to be the first to slap my wrists for sugesting a siloxane treatment to the brick. I've found it very effective on soft and damaged brick, rain and splashes just run off and it's breathable and invisible.

I used it on the front of this house after chipping of all the render and repointing in NHL. The walls where sodden behind the render and the faces of the bricks totaly shot after I'd had the breaker on it.

It soon dried out and hasn't shown any problems for the last nearly three years.

It could well sort out the splashing problem.

I'm sorry, but I wouldn't be able to live with the look of that scarring. I don't think it represents good conservation, sorry.

 

[agbagb]

I'm sorry, but I wouldn't be able to live with the look of that scarring. I don't think it represents good conservation, sorry.

That's all right, I couldn't live with the plastic windows but I have to draw a line commercially when it's rental property. It's now sound, dry, not deteriorating and looks closer to original than it did when rendered.
How long it stays dry is another matter only time will tell (wrist still stings a bit Gareth). But short term, so far, the siloxane treatment is working at keeping splashed water out and letting the wall breath.

 

[Zebra]

I shall continue to watch and monitor the damp areas but I rather fear that middi's was the answer I was looking for.

So middi, let me make sure I get this right. You cut through the wall between two courses of bricks, all the way around the house. What height, relative to the new floor level? I cannot get to the bottom 400mm of the long rear wall from the outside because of the retaining wall. Is it possible to cut through the entire 9 inches from one side only? How do you then get the dpc to go all the way in there? Do you do it in small sections and overlap them, or in one go? And then you get the floor membrane to go in there as well, just tuck it in on top? And if you can't cut the whole width of the wall from one side, and the dpc didn't go the full width, that would make it ineffective? And does the wall then settle on top of it? Does it lead to cracking or movement?

Sorry for the barrage of questions middi. I appreciate your frankness about the ineffectiveness of other options. I do only want to do this work once, not get everything finished and then find I still have a problem.

This solution though won't stop penetrating damp from water which splashes onto the wall above the dpc. What would be the way to get around that?

I understand you're saying it's up to me and not necessarily the right solution, I promise not to hold you responsible!

 

[middi]

Iserting a dpc and floor membrane into a solid ( 9 inch thick) brick wall.

1) the height of at which the dpc should be inserted into the brick wall should be about 150mm ( or 6 inches) above exterior floor level, this is a firm guideline and should be adhered to. The objective ,at this stage, is to make sure that any external surface water does not accumulate or rise above the dpc and the exterior wall above the dpc must be open to the elements, unobstructed with adequate free circulation of air. As to what one does to the external wall 150mm below the dpc is totally irrelevant. Usually nothing as it will probably be covered with soil, pathways etc.

2) the type of dpc that should be used is the standard black bitumen/plastic sold in various width from your local builders merchant. The reason for using plastic ( or soft type dpc) is that it can easily be cut with scissors or knife and extremely easy to overlap into dpm's if you want to. As you will need to cut the dpc in approx. one metre lengths and overlapped onto itself by a min of 150mm and then inserted into the wall, this dpc would be ideal for your situation.

3) the installing process and as to how quickly you will be able to install the dpc it all depends on the stability of the wall, any openings ( ie windows etc..) less than 1.2 metres above floor level and what kind of bonding has been used to lay the original bricks. A skilled bricklayer will be able to lay one metre section at the time, less confident bricklayers will only do 600 to 800 mm sections at the time. There are a number of variables which determine as to how one should proceed. Generally, a predetermined length of wall section is removed, the removal of section length should ideally be the full 9 inch wall thickness consisting of a single brick, if the bricks are loosely bonded by the older lime mortar this may involve removal of more tha one brick thicknes. If the wall is in realy poor condition a means of angle iron support may be required to avoid too many bricks collapsing in the removed section. It is a matter of judgement as to one should proceed.

4) An length of pre-cut dpc is then layered in mortar for the full length of the opening, then the bricks are relaid in mortar to refill the the gap taking care to leave at least 100 mm exposed dpc at each end for the next lot of dpc to be layered and overlapped onto it. This process is repeated untill the job is done.

5) Once the internal floor level is determined ( regardless at what height as compared to the ouside level) the width of the dpc has to be of enough width and left exposed in order for at least 300mm ( or one foot) to be lapped below any floor DPM to be used and the two membranes to be sealed at the overlap with bitumenous paint brushed in at the joints. As to what you then use to finish the internal floors above DPM is a matter of choise. Having accomplished correctly what I have described above no damp will perculate from the floor or from below the dpc brick line.

6) I would not do nothing at present with the exterior wall elevation, I would just make sure that these are correctly pointed with lime mortar, the moisture sucked in the brickwork due to rain should evaporate out very quickly. This is why soft red brick elevations are best left exposed and not obstructed with renders or paints as these can crack allowing water to gain entry onto the brickface and no other way to get out exept trough the inside of the building. There are always exeption to the rule, especially with exposed 9 inch thick brick walls, if having provided adequate ventilation, normal heat etc.. and some dampness still persists and evident within sections of internal walls then you have no choise but to line and insulate the internal walls. Normally, this should not be necessary.

I hope this helps, and application or execution may vary depending on your particular circumstance

Middi

 

[Zebra]

Perfect middi, thank you. That makes perfect sense and is a very comprehensive answer. It does sound very major, but achievable. Only a couple of possible issues arise in my mind which I'd be grateful if you'd consider:

- where the long rear wall turns the corner and becomes an internal wall, separating the old part of the house from the new extension, would it be advisable to continue all the way along the internal wall, or to stop a certain distance in from the corner? (Marked as ?1 on the attached drawing)
- where the long rear wall meets the solid base of the bread oven, I don't imagine that I can remove bricks without the stones that fill the base of the bread oven falling out and the whole thing collapsing. I won't know until I try. If I were to just stop at that corner, can you see a problem with that? (marked as ?2 on the attached drawing)

Thank you for your advice.

 

[rebeccac]

Middi, Our house in italy is limestone and we do have a house that joins us so its difficult to solve every damp problem.In the UK the house is on a hill and built partly into that hillside so we get lots of water coming down and under the house hence smells -or so we believe.

Whar dpc would you put in Italy? ouldyou not just push damp up the walls?

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