Hi All, First time posting and was hoping for some advice. I have rising damp in my living room wall. It is a solid brick wall connecting to the garden and the wall was plastered 1 year ago when I moved in with multifinish plaster. The damp surveyer came round and wanted to inject the wall with the dryzone rods but i felt like that would just be masking the problem and would rather find the cause. I decided to do some research and ended up with a spiral of information and different opinions as to what the cause could be. Below are some which relate to my case: 1) The the previous owner laid the garden patio tiles too high, butting up to the airbrick and therefore breaching the DPC. This is around the whole rear perimeter. 2) There is a small extension (again was done by the previous owner) which has cement render on it. The paint is flaking off and it looks unsightly. From what I understand, cement render isnt breathable and sucks in the moisture which could be contributing? 3) Cast iron soil pipe has branches growing out of it. I'm unable to see if it has managed to penetrate the stack or into the wall behind it (which is the living room wall), however there are no visible sign of leaks or any foul smell. I guess the only way to know would be via a CCTV survey or if I decide to replace the cast iron for a plastic one. I decide to tackle the DPC breach first, by removing the outer patio bricks and digging a trench 2 bricks below the DPC (150mm). I was hoping to find some soil which would drain the water away once I fill it with 20mm pea shingle but instead I'm at the original concrete floor which is 2 bricks below the air brick. I guess my question is what options do I have to avoid water build up in the trench? As it is concrete, the gravel system won't drain the water away so I was thinking of installing an aco drain. My problem is that the aco drain would sit only one course below the DPC, so would this not still allow rainwater splashback above DPC? Also, I would appreciate some advice on how to tackle the damp plaster on the internal wall. My original plan was to hack the plaster off to bare brick, install Permaguard dpm and then dot and dab plasterboard and plaster. However I am worried that if the damp doesn't fully dry, it was just reappear above the plasterboard and I'll be back to square one. Apologies in advance if my post is all over the place - it's an accurate reflection of the thoughts in my head! I have attached some pictures to show the issues and where I am currently at with the trench.
I would get the following addressed: Render needs cutting above the dpc , drip bead fitted and render made good. Any brickwork, mortar joints damaged during render removal made good. Gully surround may also be bridging dpc so needs separating from wall. Regarding perimeter drainage, 2 possibilities come to mind, either punch or drill through the concrete to allow drainage or if you have the depth, a perforated pipe laid under the 10mm( not 20mm) shingle and connected into the rainwater Downpipe at the connection point. Perforated/ slotted pipes are 110mm but nothing to stop you making you own with a smaller diameter. Replace any defective rainwater goods You may find that once external rectification is done that your wall starts to dry out (allow up to a month per 25mm thickness). If damp continues then rising damp could be a possibility if the dpc Is defective. will then require a dpc injection and some plaster replacement. The soil pipe / render detail looks to need attention. Properly needs to be removed to clear behind it and make good render. New pipe then fitted. AKO drains do work in a similar way to shingle in preventing the majority of rain splash so could be considered for connection as per the perforated pipe principle if you don't want to use loose stone.
Hi Mark, Many thanks for your response. I have some follow up questions and would be greatful for your input: Removing render - will i need to hack off all the render or just above where it is green and peeling? Furthermore, should I rerender it with cement render or something else and can i paint it after (to match the rest of the house). It is a small existing extension and I do have plans (not sure when) to build a bigger extension in the future so was hoping I wouldn't need to mess around too much with the existing one. But then again, id rather not have damp! Gully bricks - is it nomal for it to be open with a brick border? I also noticed the downpipe discharges to soil and not to any soakaway - is this normal or should it be connecting somewhere underground? I did initially think since its not connecting anywhere the water could be forming in the gully (which only has soil) - could this be a possibility? I did have a little dig inside it and it did seem 'dry' with no wet soil (it did rain heavily yesterday) - although not sure how deep you would need to dig to find an issue like that. Trench Drainage - good shout, I might look into drilling some holes as it would be cheaper than getting aco's - any idea how big of a hole to drill and at what intervals? And should I just drill down until the drill bit finds soil? Similar to the gully, would it be better to have an aco drain or somewhere for it to drain to or will soaking to the ground be fine? Internal wall - so would it be best to finish the works outside and leave the damp plaster for a while to see if it starts fading? Admittedly one of my worries was hacking off and replastering only for it to reappear and thus, making all the work I done pointless! Salt deposits and mould have started forming around the bottom so I've been itching to hack it off! Should I wait for it to fade completely or can I start the work as soon as I notice some improvement (as this would mean the outside work has sorted it?) Soil pipe - yes I was thinking of cutting out the section from the T joint to the ground, repairing the render cracks behind it and removing any of natures roots. I'd then replace that section with a plastic soil pipe. Not sure if it's something I should tackle on my own as the pipe looks heavy! So might need to get a quote for it.
As long as the render is sound and solid, the green should clean off. Main thing is it doesn't bridge the dpc. Once repaired you can repaint. Years back rainwater often discharged into the foul water pipework rather than a soakaway. If yours does then it can stay in that configuration. Open gullies with brick surrounds were typical also. Concrete gully fenders are available. Gully should have a guard to avoid debris causing blockages. Concerned though about your description of no visible gully and just soil. Should be one there. I would clean it out and see what you have as you don't want the Downpipe discharging I to the ground against the building. BTW I assume your patio has a fall away from the property and its only rain splash that needs to be dealt with against the walls. Re the cast iron soil stack. Yes very heavy. If you decide on Holes in concrete for drainage I would probably go at least 12mm and through to the soil and as many as you can, at least every 100mm or so. Lay a strip of permeable membrane over them so they don't block up with the shingle. Thinking further, Better still, If you are able to cut/ grind a slot and then break out the concrete away from the wall even better. Doesn't have to be the full width , 50mm would work. Once cut I would expect you could chisel it out without too much trouble once you got started. Internally ,the plaster will need to come off anyway and be replaced where damaged. Taking it off early will help with the drying out process.
Hi Mark, Many thanks for your prompt responses - much appreciated!! RE Render: I will cut back some of the render until I'm a few cm's above DPC (im assuming its above the air brick so ill aim for 1 or 2 courses above). I'm hoping to angle grind a straight line and then knock it off with an SDS. And it will all come off in a perfectly straight line for me to re render.....(I can dream). RE Gully - I will have a proper dig around tomorrow and see if I can see anything. Although since there is visible soil, I'm not too hopeful as the soil would block any pipe/drain? But ill have a better idea tomorrow. RE Trench - thanks, I'll give it a go with 12mm holes and a permeable membrane. Should I stick with 20mm shingle or would 10mm provide better drainage? The concrete does butt up to the wall but it is below DPC - are you saying it's better to separate it? RE Plasterwall - great! I'll hack it all off and see how well it dries. I'm aware it will be a slow process but hopefully will be the start of dry non-damp walls!
My thought is that the concrete is an old base or path. So if you could cut the concrete through and create a 50mm wide channel to the soil or hard-core below it would give better drainage than holes for sure. Thinking drop a grinder in to cut a slot 50mm or so from the wall. Break it out with your sds if it has a hammer stop. If its too difficult then the holes is next best. Rain deflects and bounces less on 10mm shingle than 20mm. If you cant locate any gully then may be prudent to get a drainage specialist in to look at that issue ( and the soil stack maybe) Hope it all works out.
Hi Mark, Hope you have been keeping well. Just an update on this and was hoping to get some more advice: 1) Trench has been dug around the perimeter including removing some of the old concrete base (so I am down to the soil now finally!) The bricks below the DPC are wet but above it are dry - can I conclude there are no issues with the DPC? There were rendered plinths covering the DPC which were rotten. I have removed these now and just have exposed bricks. Should these bricks dry out or is it normal for them to remain wet throughout? 2) The bricks below (and some above) DPC are in terrible condition with many gaps in the crumbling mortar. What would be the best mix for repointing these before filling the trench with gravel? I read that it if lime was originally used in the mortar, it should be repointed with the same. But I can't tell or wouldn't know how to identify this. It is a 1930's property if that helps. 3) When filling with gravel, can I fill it above the DPC to make it level with the current patio slabs? Or do these also need to be below the DPC? I was hoping to level it out to the existing patio to avoid any step (especially with a little one!). My thinking is that this would still allow moisture to evaporate as it is only 'breached' by gravel? 4) The trench has left a gap between the patio door and the current slabs. I read that as it is an opening, the DPC can be bridged if it is for a step - is this true? There is an airbrick there which I wouldn't cover, but can I reinstate the brick paving below the patio door sill to make it level? 5) Lastly, the render that I hacked off has left roughly 30mm from the brick to the existing render - how would I install bellcast beading and blend in to the existing render? Do I just secure the bead to the bricks during the scratch coat and then just build it up on second coat? Apologies for the long post! Your advice is much appreciated!
1. Bricks will often stay wet below dpc but if dry above sounds like dpc is working ok. 2. Probably Lime but for making good I would go 4:1 building sand/ cement. If you want to try and match the colour white cement is an option . Also you can cement over spalled bricks and then mark them out square to resemble the brick again, followed by a coat of black or other colour masonry paint. Bitumen is often used in this situation but this won't allow moisture to evaporate out and therfore slow up the drying process. 3. can be done but not ideal as it remains wet within the stones for a lot of the time. An option is to chamfer from the slab edges but not too wide with mortar and push stones into this before filling the majority of trench with loose 10mm shingle . Hopefully will reduce the trip hazard. 4. Once filled in solid below the step, splash to some degree will go up the doors but if that's not an issue for you then you can go up to the dpc which may be on the course directly under the cill. If your paving will finish above dpc then it will bridge, and the damp will in time damage any timber cill and internal threshold etc. (appreciate your cill is upvc) and can push into the floor inside. Only way around this would be to put a vertical dpc between slabs and wall but only within width of doorway. 5. Bellcast can be nailed to brickwork joints with galvanised nails and then render, 2 coats if needed. If you need to pack the bead out then mortar can be used as you suggest. A diluted sbr helps with render Bonding etc. Damp walls take around 25mm per month to dry out. Hope it all goes well.
Hi Mark, Thanks for your insight! Annoyingly the good old British weather meant I couldn't tackle the outside this weekend as planned. So I decided to hack off the internal plaster. I hacked off 1.2m from the ground (this is 30cm higher then the highest tide mark). I thought I would see wet bricks but to my surprise all the bricks are bone dry. I'm wondering whether I had rising damp in the first place? The DPC is below the timber floor but as the bricks above are dry, do I need to mess around and remove the floor boards to have a look? My theory is that the "original" plaster was wet/damp and when my builders plastered over it last year, and the moisture naturally came to the surface of the new plaster. In this case, since I don't need to wait for anything to dry, am I okay to plasterboard over using dot and dab foam, and get it skimmed? Or would you reccomend any additional checks just to be on the safe side. The dust accumulated from hacking off has been a nightmare so I am hoping this is the first and last time I need to do any internal works! Thanks
If you had a tide mark showing then that would suggest the damp extent ...at the present time. Limited moisture won't always be that visible on the brick surface when you strip the plaster. Going to the extent that you have, I would be inclined to pull up a couple of boards and check the sub floor timbers. Probably worth mentioning that when walls dry out and are re plastered, salts within the wall can work their way to the surface and show as marks and a white fluffy dust like deposit. A moisture meter reading would confirm if damp is actually present. If it is then the usual procedure anyway is to render internally with a salt inhibitor incorporated. Damp proofing companies use this and in fact the additive used also contains a waterproofer. Then a skim applied and not over troweled to allow drying to pass out through the surface. If you are completely sure there is no moisture then it could be treated as a normal internal wall skin and dot and dab finished but if there is any moisture this would eventually fail as damp will over time Probably cause the adhesive to fail ( using foam over wet adhesive is probably a better bet in this situation although i dont use it myself) and also transmit damp through to the surface as well as breaking down the plasterboard
Hi Mark, Thank you for going on this journey with me! After your helpful post, I done some research and was planning to do the following to be on the safe side: 1) Install dryzone rods - As mentioned the DPC seems fine but I'd be doing this as a precaution.it says to insert them at the lowest mortar course line visible. As mine is a concrete block with the visible line slightly higher up - would this be okay? Also I know it's a 12mm hole 120mm apart, but how deep should I drill? 2) Dryzone Shield Cream - as you mentioned regarding the salt deposits, this was definitely present on the plaster so this should help to tackle that. I'll apply one coat all over. 3) Dryzone dry grip adhesive - this might be more suitable than the foam for the plasterboard as it supposed to be salt and damp resistant. I'm not sure how well it's grip would be so can I use this in conjuction with the foam? 4) As part of their "set", there is a liquid DPM that can be applied to complete the damp proofing - is this necessary? If I do apply it, should I paint it up to the concrete block? Thanks in advance! I'm hoping I'm on the home run!
Hi again 1. I use the injection cream rather than the rods but expect they would work as well. Yes, drill internally at the lowest joint visible above floor level . Drill to within 20mm or so of the wall brick thickness. I install at 100mm spacings rather than 120mm. If you wish to isolate the wall you are treating from an adjoining wall and reduce the risk of any damp tracking across then you can also drill vertically in the mortar joints tight in the corner and also inject there. 2. Not used the cream you mention but expect it should do as it says on the tin. 3. Not used that also but probably best to go with compatible products. 4. Their liquid dpm sounds like a tanking slurry / equivalent which is usually applied to any exposed masonry/ brick etc below the new dpc level. Any damp in the wall held back by the slurry will be compromised if you drill through it so use an adhesive to fix skirtings etc.
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