Penetrating Damp in Victorian House

elenapopaphoto

Hello folks,

I'm getting so frustrated with all the damp issues in our first home. We bought it 6 months ago (may have been the most idiotic decision) and still haven't been able to install a kitchen due to the damp issues that seem to not want to be resolved. It is a 1900 Victorian terrace, with a rear two storey 'extension' that was added to all houses in the neighbourhood, but not sure when - could be 30s, could be 50s. Very common for Victorian terraces. This rear extension is made out of concrete blockwork, and brick in the corners and window surrounds. The floor is poured concrete onto clay, and the walls only go down about a foot  below the internal floor level and are sat directly onto clay. Two-skinned wall with cavity. This is where we are trying to put in the kitchen. 
The concrete patio outside is slightly higher than the internal floor, so we have had builders put in an external plastic ACO drain running just outside the wall. This was sealed onto the wall with cement render which gets wet with any rainfall and the wetness can be seen to rise up a few inches on the wall. We did initially want to drop the patio level outside but this was quickly dismissed by our builder who said that because the foundation is so shallow, this may destabilise the building. 
On the inside wall (which is plastered with gypsum plaster) we are getting a visible 6 inches of water from the internal floor level up. We have been running a heater and dehumidifier constantly over the last few months to no avail. 
I have spent the last week obsessing about this and it's driving me absolutely insane. We will want to sell this place in a couple of years time and I worry that any crazy person willing to buy it won't even be given a mortgage for it. Not having a proper kitchen for so long is also adding to the stress.
I should also add that there is no evidence of a physical DPC, and the builder said that to add one in would be a mammoth job.

Picture of the outside and wall in question attached (Render patches are from where we've had the old windows put back in, some idiot blocked them up badly back in the 90s, bridging the wall cavity, which we have now rectified)

Help.
 

Any suggestions/thoughts appreciated (I don't believe in chemical DPC however so please don't suggest that)

Apodemus

I'm not sure that the ACO drain was the best option - assuming what we are seeing is an open plastic drain with a grid cover.  That will do a good job with any surface water but might be leaving you with damp soil and ground water against the wall at a higher level than your internal floor.  I would have thought that a decent french drain would have been better although that might have had to be located slightly further out from the foot of the wall, to avoid your minimal foundations.

Even if everything was fixed properly, it might take a good few months for the wall to dry out, so I wouldn't necessarily give up hope just yet.  A rough rule of thumb is often given as a month for every inch of thickness in the wet wall. and you probably have at least eight or nine inches of concrete block there to dry out.

Doozergirl

As above, but I'll be more brave than Apodemus and say that the ACO drain definitely isn't appropriate.  For the same reasons.  You cannot have anything touching the wall above the floor level. 

You need a French drain, with the ground level immediately adjacent to the wall at 150mm below floor level.  Your patio can be higher but it must definitely be sloping away from the house.  If the patio isn't sloping away then you can use the  ACO drain, but it MUST be below your floor level.  

You won't destabilise foundations because that ground level can't always have been that high or it would always have been soaking wet. It's almost always subsequent landscaping that causes the problem. 

tacpot12

Do you know if the floor has a DPC under it? You might be able to see the polythene sheet around the edges of the floor. 

 If it doesn't, then you have another problem. If there is no DPC under the floor and none in the walls, you might be better off knocking the extension down and restarting with proper foundations. Although this will be expensive, it will cure the problem and give you complete confidence that that part of the house will be dry. You will also be able to improve the insulation under the floor and in the walls, to get better efficiency. 

elenapopaphoto

Apodemus said:

I'm not sure that the ACO drain was the best option - assuming what we are seeing is an open plastic drain with a grid cover.  That will do a good job with any surface water but might be leaving you with damp soil and ground water against the wall at a higher level than your internal floor.  I would have thought that a decent french drain would have been better although that might have had to be located slightly further out from the foot of the wall, to avoid your minimal foundations.

Even if everything was fixed properly, it might take a good few months for the wall to dry out, so I wouldn't necessarily give up hope just yet.  A rough rule of thumb is often given as a month for every inch of thickness in the wet wall. and you probably have at least eight or nine inches of concrete block there to dry out.

Doozergirl said:

As above, but I'll be more brave than Apodemus and say that the ACO drain definitely isn't appropriate.  For the same reasons.  You cannot have anything touching the wall above the floor level. 

You need a French drain, with the ground level immediately adjacent to the wall at 150mm below floor level.  Your patio can be higher but it must definitely be sloping away from the house.  If the patio isn't sloping away then you can use the  ACO drain, but it MUST be below your floor level.  

You won't destabilise foundations because that ground level can't always have been that high or it would always have been soaking wet. It's almost always subsequent landscaping that causes the problem. 

Thank you both for your input. I should probably add that the trench beneath the ACO drain was filled with cement. So there is only cement underneath the plastic, then the clay. Does that make any difference at all? Will we have to undo all this and install a French drain? 

elenapopaphoto

tacpot12 said:

Do you know if the floor has a DPC under it? You might be able to see the polythene sheet around the edges of the floor. 

 If it doesn't, then you have another problem. If there is no DPC under the floor and none in the walls, you might be better off knocking the extension down and restarting with proper foundations. Although this will be expensive, it will cure the problem and give you complete confidence that that part of the house will be dry. You will also be able to improve the insulation under the floor and in the walls, to get better efficiency. 

Do you mean underneath the poured concrete floor? No idea, but there doesn't seem to be any sign of it. Rebuilding the back of the house is out of the question - it's a terraced house, so we share the extension with our neighbour, and we wouldn't have the funds to do it anyway. Thank you for your suggestion though.

stuart45

Is there any debris in the cavity?

Doozergirl

tacpot12 said:

Do you know if the floor has a DPC under it? You might be able to see the polythene sheet around the edges of the floor. 

 If it doesn't, then you have another problem. If there is no DPC under the floor and none in the walls, you might be better off knocking the extension down and restarting with proper foundations. Although this will be expensive, it will cure the problem and give you complete confidence that that part of the house will be dry. You will also be able to improve the insulation under the floor and in the walls, to get better efficiency. 

That's a bit extreme!  As long as a house can breathe, the lack of a DPM isn't the end of the world.  There will be many, many kitchens without DPMs without serious issues.  The main problem here is the ground level being higher than floor level.  

Doozergirl

elenapopaphoto said:

Apodemus said:

I'm not sure that the ACO drain was the best option - assuming what we are seeing is an open plastic drain with a grid cover.  That will do a good job with any surface water but might be leaving you with damp soil and ground water against the wall at a higher level than your internal floor.  I would have thought that a decent french drain would have been better although that might have had to be located slightly further out from the foot of the wall, to avoid your minimal foundations.

Even if everything was fixed properly, it might take a good few months for the wall to dry out, so I wouldn't necessarily give up hope just yet.  A rough rule of thumb is often given as a month for every inch of thickness in the wet wall. and you probably have at least eight or nine inches of concrete block there to dry out.

Doozergirl said:

As above, but I'll be more brave than Apodemus and say that the ACO drain definitely isn't appropriate.  For the same reasons.  You cannot have anything touching the wall above the floor level. 

You need a French drain, with the ground level immediately adjacent to the wall at 150mm below floor level.  Your patio can be higher but it must definitely be sloping away from the house.  If the patio isn't sloping away then you can use the  ACO drain, but it MUST be below your floor level.  

You won't destabilise foundations because that ground level can't always have been that high or it would always have been soaking wet. It's almost always subsequent landscaping that causes the problem. 

Thank you both for your input. I should probably add that the trench beneath the ACO drain was filled with cement. So there is only cement underneath the plastic, then the clay. Does that make any difference at all? Will we have to undo all this and install a French drain? 

In a word, yes.  There should be nothing touching the wall beyond 150mm below what would be the original DPM, your floor level.  It doesn't matter what it is.  Concrete, paving, Aco drain, soil, foliage.  Nothing.  
 

tacpot12

Doozergirl said:

tacpot12 said:

Do you know if the floor has a DPC under it? You might be able to see the polythene sheet around the edges of the floor. 

 If it doesn't, then you have another problem. If there is no DPC under the floor and none in the walls, you might be better off knocking the extension down and restarting with proper foundations. Although this will be expensive, it will cure the problem and give you complete confidence that that part of the house will be dry. You will also be able to improve the insulation under the floor and in the walls, to get better efficiency. 

That's a bit extreme!  As long as a house can breathe, the lack of a DPM isn't the end of the world.  There will be many, many kitchens without DPMs without serious issues.  The main problem here is the ground level being higher than floor level.  

Yes, I realised that it was a bit extreme, but the OP did say that they had already had advice not to drop the patio level as it may destabilise the building. If the floor has no DPC under it, damp is going to be a persistent problem. I agree that making sure both the inside and outside walls can breath will help in the absence of a DPC, but the OP has been waiting a long time for this to happen already, and the ACO drain was put in to make things better so it was already a problem even before the ACO drain was installed. I just wonder if remediation to the walls is really capable of sorting this out. 

I've always wondered how watertight the ACO drains are when clipped together. It is possible that some rainwater is leaking from the drain into the foundations and not being taken to the sewer?

Doozergirl

tacpot12 said:

Doozergirl said:

tacpot12 said:

Do you know if the floor has a DPC under it? You might be able to see the polythene sheet around the edges of the floor. 

 If it doesn't, then you have another problem. If there is no DPC under the floor and none in the walls, you might be better off knocking the extension down and restarting with proper foundations. Although this will be expensive, it will cure the problem and give you complete confidence that that part of the house will be dry. You will also be able to improve the insulation under the floor and in the walls, to get better efficiency. 

That's a bit extreme!  As long as a house can breathe, the lack of a DPM isn't the end of the world.  There will be many, many kitchens without DPMs without serious issues.  The main problem here is the ground level being higher than floor level.  

Yes, I realised that it was a bit extreme, but the OP did say that they had already had advice not to drop the patio level as it may destabilise the building. If the floor has no DPC under it, damp is going to be a persistent problem. I agree that making sure both the inside and outside walls can breath will help in the absence of a DPC, but the OP has been waiting a long time for this to happen already, and the ACO drain was put in to make things better so it was already a problem even before the ACO drain was installed. I just wonder if remediation to the walls is really capable of sorting this out. 

I've always wondered how watertight the ACO drains are when clipped together. It is possible that some rainwater is leaking from the drain into the foundations and not being taken to the sewer?

The ACO drain has been fitted entirely incorrectly in the wrong place.  I suspect the builder is talking rubbish about the foundations being a problem.  I've said this all above, but that extension was not built with the ground level as it now appears.  

Back in the days before DPMs, houses did not have them at all.  If the floor is able to breathe, they shouldn't be a problem.  I can see what the main problem is.  If the excess water ingress stops, under the floor will also eventually dry out enough to not be a major problem. A liquid DPM could always be laid to the floor to protect any new flooring above it - knocking the thing down shouldn't even be a consideration.  

Checking that all the water from the drains goes to the right place is a very good idea.