How to protect front house wall from damp and water ingress (Ed.).

[DeninSS]

Hi all,




I was directed to this site by my web search regarding project I am planing to do but before I do anything I was in the hope to get some advice.





I live in a semi detached house build in 1906 which you can see from the pictures I have attached, sits non-elevated from main road and has a front garden with pile of soil.





In need to tackle possible future damp issues (as we had in the past) due to the wet soil always being close to bay brick wall and making constantly wet. I was thinking to build a retaining wall if that is the correct expression in order to keep house bay wall(or entire wall) free from soil, thus protecting from any moisture ingress. In addition, I also was thinking to build some sort of either air flow within that cavity (between house wall and retaining wall), or fill it with stone and lay then patio on top. These are ideas I would welcome best advice how to prevent wall getting wet.





So we have started the work, by removing the soil from brick wall that was at the bottom running across garden. House was repointed with cement or NHL, and I thought since i have space and time to repoint in proper hot lime.





Now I am slowly excavating the garden in order to make a space for retaining wall but not sure how to approach this project. Can that wall be built there, how thick would it have to be ( I read at least 210 mm), how far would I have to dig for the foundations, how far does the wall needs to be apart from house, does it need council approval, structural engineer etc. Would you recommend doing it at all? Can I fill different material within the cavity (house front wall and soil) I dug save soil? I don't want the space to be filled again with soil due to damp wet soil can create, so I ponder how to approach this correctly.





Also i wanted to know how close i can excavate to the front of the house wall.


I was told i would have to leave at least 300 mm of garden and then add a retaining concrete block wall going across and then in a gap between this wall and the garden behind it, pour in concrete, or stones.





So yeah thats it, just wanted to know how much garden/land i need to retain from the house wall, how far back we can dig to make walls dry as long as possible.Would you advise to do this? What could be alternative without risking the foundations of the house to compromise, if that is the case.





I also want add two air bricks on each side, but I am not sure do I need a lintel to support the wall, or can I just chisel out bricks and install an airbrick.

Can anyone please advise me how to approach this problem, how to tackle it, what to do with this cavity now. Can I build retaining wall, would that be advisable approach. Any ideas would be much appreciated. This has been going on for last five years since we moved into the house, neglected by previous owners. Joist were rotten, had to replace them too.



Thank you all.

 

[clifford1]

has a front garden with pile of soil.

Not clear what you mean by this. Someone has dumped a pile of soil in the garden? Why not just remove it?

 

[DeninSS]

Thanks for your response.
Oh no soil was there, level of the soil was close to cover completely air brick vent. I am working on removing it from there as it was main culprit for dump issues. As you can see from photos, I have already remove one part of it, the one adjacent to outer house wall. My question is really, what can I use to fill that void, gravel? Am I going to have problems with foundations if I remove soil and replace it through gravel. What gravel the would be best? I read that river stones not less than 40 mm is best to use, or lime stone. Do I need any kind of dump protection sheets before I insert gravel into the void which would prevent any water or soil moving back towards wall? Furthermore, my original idea was to build retaining wall but then I would have to dig deeper, and I don’t think it would be an option now for me as I think better option would be to remove as much soil as possible and replace it with material that does not accumulate water and transfer it to walls.

 

[JohnD]

Can you see the original DPC? Where is it? I'd expect it to be either under or on top of the air brick.

What is the height of the joists, relative to the airbrick? Are the bricks in pockets in the external wall, or is there a sleeper wall? Is the cavity empty?

Is there a cellar or basement?

What is under the floor? A deep void? Then earth? Or concrete?

Is the house on a hill, or is the ground level the same?

Does water run or collect beside the house?

Please stand back and take wider pics, all the way up to the roof and down to the ground, showing the eaves, gutters, downpipes, soil pipes, waste pipes and gullies, indicating the ones that are leaking.

Where is the water supply pipe, and where are the damp patches?

I can only see one airbrick. That is not enough. One every metre, on at least two sides of the house to provide a throughflow of air, is not too many.

Is it lime mortar?

 

[JohnD]

A trench 300mm wide will be enough. You can fill it with cobbles or pebbles (the larger the better) not gravel. This will prevent water rising by capillarity and will allow rain to drain away. The height should be 150mm or more below the DPC. You can use broken or irregular stones, but round ones are better. Crushed stone is not so good. You can finish with an ornamental layer of pebbles on top. If necessary lower the garden so it is no higher or mud will wash into it.

Do not fill the trench with concrete.

The backfill has to be clean and free of mud or soil. You do this by lining the trench with landscape fabric which acts as a sieve or filter.

 

[DeninSS]

Hi JohnD, thank you for your reply, indeed DPC is above air brick, and that’s the only one originally installed. There are four I think on the left side of the house and one at the back. You are right there should be more air bricks at the front. I was thinking to install additional Ones but then builder of mine dissuaded me from doing it as it would let to much cold air in winter. Anothe4 mentioned possible need of a iron lintel as it is solid wall, I think 12 inch. So, the moment I heard lintel and potential structural compromise of the house I didn’t even think anymore to do it. Therefore, I posted question regarding lintel for air bricks too here in forum.


Joists are on the same height as the air brick, I think one photo is available where air brick is shown from inside siting along the conterminous joists. I am not sure to understand your question “bricks in pockets in external wall”, please clarify. If you refer to the brick wall it is solid brick wall no cavity. No sleeper wall.


There is no cellar nor basement, it is ventilated void approximately 1m deep from the joist to the bottom. The bottom is probably lime-floor sitting on soil or maybe bricks. I cannot tell as I haven’t dug it out.


House was build back in 1906, all lime, no cement.


House is not on the hill. Well ground level is definitely higher, approximately at the same length as the soil that was filled in the front garden nearly up to the middle of the air brick.The front garden is bordering with small parapet opposite the front wall (air brick bay wall). Behind that wall is walkway a the next to it is a road.


On the left side of the house, (looking at air brick bay wall photos) is actually our house entrance which is provided by small concrete path maybe 1m wide and 10 long. One access garden entrance as well via this path. Water runs through that path. On the left side of that pathway is neighbours house entrance. On the right side of the house is again our neighbour’s house attached to ours. It is semidetached house.


I will take more pics tomorrow and post them here. I have taken few now but it is dark here, hence sorry for the poor quality.




Where is the water supply pipe, and where are the damp patch


There is one water pipe that runs from roof to garden and then again through another pipe to the street walkway. Now regarding, damp patches, from the inside of the house, patches had been on the left part of the wall (which you can see them even now) . One brick on the same left wall is still a bit dump even though the ones around it are not. Not sure what’s is going on there. Exactly that brick would be replaced though air brick. That part of the wall was soaking wet, but it dried out except that brick I mentioned. On the right side of the wall as you can see brick wall exposed, the lime mortar just fell down due to dampness, I have tried to re plaster it but stopped doing it as it was dump. The right side of that part wall ( right under the brick wall to the right under the joist is still dump if not wet. Floor board had been up for last month and ventilated all day long and dump has disappeared apart from the part of the wall (brick exposed-lime-mortar-Fell-down-wall). I suspect that water supply or gutter pipe is somewhere leaking under the path as we have some cracks in concrete pathway. On both sides of mine and neighbours bricks under dump course are socking wet, weed growing out of them. If that’s the case, if the pipe is leaking under, then that could be the reason why the wall(under the pathway) is all the time wet. That was the main reason to add additional air brick As I don’t know how to tackle the problem properly.

 

[DeninSS]

A trench 300mm wide will be enough. You can fill it with cobbles or pebbles (the larger the better) not gravel. This will prevent water rising by capillarity and will allow rain to drain away. The height should be 150mm or more below the DPC. You can use broken or irregular stones, but round ones are better. Crushed stone is not so good. You can finish with an ornamental layer of pebbles on top. If necessary lower the garden so it is no higher or mud will wash into it.

Do not fill the trench with concrete.

The backfill has to be clean and free of mud or soil. You do this by lining the trench with landscape fabric which acts as a sieve or filter.

Ok thanks, have to dug then a bit more to extend the width and lower the ground as well. I will get these days round cobbles or pebbles the larger section (which exactly is the size of the larger, >40 mm?), can you advise please? Also, Is there specific landscape fabric to be used? Is it the one to be used for gravel so the water can get through but not soil. Do I have to use damp proof fabric anywhere to protect the void? I also plan to lay small patio (because there was one before the damp issues) on the reaming part of the soil, next to the pebbles around the flour bed. Would you advise it to do that? Sorry many questions, many thanks for your help, really appreciate it.

 

[JohnD]

I didn't know there were multiple grades. Yes, water but not soil. It's a sort of fine black nylon mesh or coarse gauze. It comes quite wide, will probably be enough for two layers.

If you want paving, prepare the ground so it slopes away from the house, causing rainwater to run away. Allow the ground to finish settling before laying.

The pebble size can be as big as you want, you will only see the top layer. 40mm is about egg size, I would avoid anything smaller, except for the top layer, as large stones are awkward to walk on. Cobbles are around 100mm cube.

No need for a damp proof membrane. Water will be absorbed into the brickwork upwards, from the ground, and if exposed, it can evaporate, which is desirable. You have a good deep void, so if well ventilated with airbricks, will be able to dry out. Water does not rise far in clean exposed bricks.

The more fresh air in the void the better. Draughts may come up through the gap under the skirting board, you can pack round the edges of the room by pushing loft type mineral wool between the joists. It will stuff in tightly to block draughts. If you have no carpets or are agile, you might like to pack it between all the joists to reduce heat loss more. Floors lose heat by draughts, very little by conduction, none by convection. I have some pics somewhere.

As you have lime mortar you can easily cut out bricks to add new airbricks.

If the joist ends are not on sleeper walls, they must be built into the brickwork of the wall. Poke the ends with a fiat screwdriver to check for rot

If you have a few wet patches there are probably leaks. Post some pics of the area inside and out, including pipes, drains and manhole covers and we can look for clues. Clay pipes and gullies are usually broken.

You dig out the wet ground until you reach the leaking pipe, expose it until you reach sound pipe, remove the broken part, replace with new, provide support, backfill. It is easy if you are fit enough to dig. There are plenty of threads about gullies. Don't add it to this one, it is already too long.

P.s.
Long term leaks wash away lime mortar leaving gaps. You can hose them out and repack with stiff mortar. It is OK to use cement mortar below the DPC.

 

[JohnD]

Here we are

 

[JohnD]

if you are packing mineral wool between joists, you need to support it from underneath, so it does not fall through. some people staple galvanised chicken wire net to the joists, but if you are buying landscape fabric, that will do. If there is a cellar it can lie on the ceiling, if any.

some people use foam insulation board, which is more expensive, but you have to cut or foam it to a perfect fit to stop draughts. Mineral wool packs into irregular gaps and does not need to be accurately cut. The draughts are worst beside external walls..

 

[DeninSS]

Thanks again for very informative response. I will have a look at varieties of black nylon mesh. I was also being busy today, excavated some soil and remove from the garden (please see photos). I remember you have mentioned that the width for pebbles should be around 30 cm, now it is a bit more in my case as I wanted to have straight line between ends of the garden. Now would that be problem if there is more pebbles than in terms of amount of rain that would flow down through pebbles? Would I overdo it with drainage if more pebbles are placed down. I remember that you mentioned that water will be absorbed into the brickwork upwards, from the ground, and if exposed, it can evaporate, which is desirable. Due to the good deep void, if well ventilated with airbricks, will be able to dry out.Hence I am asking, sorry being a bit inquisitive.
My neighbour, mentioned that this new widened void I created today (please see pics) is too much (whereas I wanted more pebbles than soil), also he mentioned that I should use some sort of cast iron slotted channel and stick as much as eight of them into the soil and bolt them to marine plywood that has been primed with bitchumen the side that would face side the soil. He also mentioned that some sort of membrane must exist between pebbles and soil. I said that i would use some sort of mesh membrane but wasn’t convinced that this would be enough. I am sorry, I just want to hear your opinion about it.Thank you.




If you want paving, prepare the ground so it slopes away from the house, causing rainwater to run away. Allow the ground to finish settling before laying.
I will do that’s but have question, which way the soil should slope away. Okay, as you said away from house but hen it will go straight into garden flower. As this garden is closed off kind of, meaning there is no way that water can escape onto the pathway or anywhere else but into the soil, should all outer reaming soils be sloped towards garden flower?
Does the the garden flower needs to have any drainage as it will be surrounded by 2-3 brick courses? Do I need any membrane in garden flower? Many thanks





The pebble size can be as big as you want, you will only see the top layer. 40mm is about egg size, I would avoid anything smaller, except for the top layer, as large stones are awkward to walk on. Cobbles are around 100mm cube.
I think I will stick to the pebbles. I didn’t come to do search where to buy them, but I will have to order them in large bag rather buying them bag by bag, and defiantly I will look for >=40mm.








The more fresh air in the void the better. Draughts may come up through the gap under the skirting board, you can pack round the edges of the room by pushing loft type mineral wool between the joists. It will stuff in tightly to block draughts. If you have no carpets or are agile, you might like to pack it between all the joists to reduce heat loss more. Floors lose heat by draughts, very little by conduction, none by convection. I have some pics somewhere.
We do have additional flooring that covers the original floor boards, so I hope that would be enough to keep that draught in bay. You can imagine, what fun it was to lift not one but two floor boards . I was not originally planing to do any insulation for underfloor void. We were really worrying not to create more dump problems, hence we left it for now, but many thanks for the pics, it looks as it was always there.





As you have lime mortar you can easily cut out bricks to add new airbricks.
Okay, yes, the lime mortar itself much easier to remove than Portland cement, I had no difficulty to rake the few mortar bits out of the brick work. The only worry for me when replacing brick with air brick is the structural integrity of the wall if I drill air brick and install one. Do I then need a lintel because the wall is 12 inch thick? Do I drill from outside or inside?



If the joist ends are not on sleeper walls, they must be built into the brickwork of the wall. Poke the ends with a fiat screwdriver to check for rot
Yes they are built into the brickwork of the wall. Almost all of them except three original one had to be replaced. They were rotten at the end (where joist meets brickwork) and mostly full of wood worm infestation. I knocked on most of them for few seconds and wood worms fell out. I treated all the remaining sound and new joists with special chemical for wood protection. I think when the dump problem is tackled there want be worries for the wood worm.



If you have a few wet patches there are probably leaks. Post some pics of the area inside and out, including pipes, drains and manhole covers and we can look for clues. Clay pipes and gullies are usually broken.
Ok I will do that tomorrow. I lifted today manhole, the one that lays on pathway, it’s on the left side of the house looking at bay window,well, to me as layman nothing seems to be clogged up, water flow is normal, but then I dug a bit as far as could under the path very close to the wall that is still wet (you can see perhaps from pics) I was able to feel that there the soil seems to be much wetter than back at beginning of the hole. I could not dig any further as the path itself is in the way, and there is weed root thick maybe 2cm protruding out of the hole.






You dig out the wet ground until you reach the leaking pipe, expose it until you reach sound pipe, remove the broken part, replace with new, provide support, backfill. It is easy if you are fit enough to dig. There are plenty of threads about gullies. Don't add it to this one, it is already too long.
Yes, no problem with digging so far, but I am not sure that this path can be dug out without some sort of council permission,
As this is not in our property domain. I would have to remove the concrete and search for the problem which would make the access to the both houses very difficult. I thought,to call, drainage cctv guy to inspect the pipes first and then to dig after. According to council, this drainage is not even mine, it belongs to my neighbours. Sorry only had chance to take few picks this morning. I will do more tomorrow.





P.s.
Long term leaks wash away lime mortar leaving gaps. You can hose them out and repack with stiff mortar. It is OK to use cement mortar below the DPC.
Okay, that’s sounds great, I will have to do repointing of the whole wall very soon. Many thanks for your help and insights.

 

[JohnD]

Too long, sorry. Try to cover one point af a time.

It is quite common for neighbours and passers-by to comment and offer advice. It may or may not be correct.

The iron grilles are used in concrete, when a drainage channel pipes the water away. You are using a sort of soakaway, which is different. The pebbles allow water to drain and to evaporate, and prevent damp soil lying against the wall and transmitting water by capillarity. What sometimes used to be called "rising damp"

The idea of putting a damp proof coating on an existing wall is old, but does not work. It will not prevent water entering the wall from below. It will however prevent evaporation. Many old houses have plinths and bitumen that was unsuccessfully attempted. Below the damp course, it is normal for a wall to be damp. The damp will rise until it reaches the point where evaporation is equal to absorption. In my house that is one or two courses of brick above ground, it does not even reach the DPC. You have lime mortar which may be different. Additional airbricks will encourage evaporation from the inside surface.

Additionally, you have a particular problem causing wet patches, which IMO are probably caused by escape of water from pipes or drains, which need to be repaired. This is a separate matter.

 

[JohnD]

"The only worry for me when replacing brick with air brick is the structural integrity of the wall if I drill air brick and install one. Do I then need a lintel because the wall is 12 inch thick? Do I drill from outside or inside?"

You can cut out lime mortar with a bread knife. I don't think you need a drill. A bolster chisel will do it. Remove the mortar, don't try to smash the brick. Take out one piece and the wall will not fall down. You do not need a lintel. Mortar in your new airbrick, then do another. You can actually take out quite a lot of bricks, but I think you will feel more comfortable doing one at a time. It will be better if you work from both sides of the wall when removing the bricks as they will be staggered and you will need two half-bricks on the inside. The new airbrick, mortared into place, will prevent the brick above from falling out, but brick walls are made so that is very difficult.

 

[JohnD]

In the pics I think I can see a white bloom on the bricks near the alleyway. If so it is probably lime from hard water, suggesting a plumbing leak. Do you have a water meter? The bloom will be worst round the leak, if there is one. If it is the same everywhere it might just be from chalky ground, and you would see it on all the houses in your street, up to the DPC but not above.

 

[JohnD]

As for the flower garden, in most cases rain that falls on the ground just soaks in. You get damp where there is a drain or pipe leaking at a particular spot.

Clay soils can form a waterproof layer, and you will see rain lying on it, in these cases a French Drain can be used, but I doubt that would be needed in your little garden. If you dig over the flowerbeds rain will soak in.