Damp internal wall

[Susana]

Hi, I am in the process of looking to purchase a Victorian end of terrace house. The inside end wall is damp up to around a quarter of the way. I have taken pictures of the exterior wall and from what I can gather the black curved area on the ground may be covering the existing dmp and the air bricks appear to be blocked when I poke inside them. We have decided to maybe hack off the black curved area you can see and replace the air bricks. Or could it be the render on the exterior wall causing the damp inside? The room inside has cement beneath the floorboards.I have added some pictures to see if anyone has any idea if I am barking up the right tree. Thank you in advance for any pointers,

 

[Cubist]

Before you do anything else... can you confirm that there are wooden floors in the ground floor rooms associated with that wall? If they are solid floors then clearing/replacing the air-bricks is pointless. Also, removing that concrete fillet from beside the wall may also be a bad move. I suspect its purpose is to keep rainwater away from the wall to limit/constrain rising damp issues.

Also, Damp Proof Courses (DPC) were made standard in the UK during the 1870s so it's possible this house benefitted from having one but that would have to be confirmed. A Damp Proof Membrane (DPM) beneath the ground floors would be highly unlikely unless concrete floors had been poured in the mid/late 20C.

 

[Susana]

Before you do anything else... can you confirm that there are wooden floors in the ground floor rooms associated with that wall? If they are solid floors then clearing/replacing the air-bricks is pointless. Also, removing that concrete fillet from beside the wall may also be a bad move. I suspect its purpose is to keep rainwater away from the wall to limit/constrain rising damp issues.

Also, Damp Proof Courses (DPC) were made standard in the UK during the 1870s so it's possible this house benefitted from having one but that would have to be confirmed. A Damp Proof Membrane (DPM) beneath the ground floors would be highly unlikely unless concrete floors had been poured in the mid/late 20C.

Hi, thanks for your reply. Yes there are floorboards on the ground floor but with concrete beneath! I can vaguely see a dmp on the front wall of the property….

 

[IHateDamp]

What are we looking at on the ground; is it your path or your driveway?

Does the concrete floor support the wooden floor or is it set down from it?

 

[Susana]

The ground you can see is a pathway so not part of the property. It felt solid when we walked on it, so not sure tbh. We only. went for a viewing so have limited details I’m afraid. Thank you for your response.

 

[IHateDamp]

I was going to suggest you looked at this thread https://www.periodproperty.co.uk/forum/threads/hotel-dampifornia.18096/

where they had a house covered in unbreathable render which trapped moisture in the wall, but just removed the bottom bit and then got the drainage in hand, and also created a 'Zebcom' trench to expose the lower brickwork to the air so that it could dry off and relieve the damp.

If you don't own the path, would who ever does be amenable to you digging a narrow trench at the side?

I'd like to know where the outside ground level is in relation to your floor level

When it next rains you may want to have a look at where all the rainwater goes/flows.

All that grey gunk is probably bridging the dpc and smothering and suffocating the brickwork so that damp walls can't dry out, and yet as Cubist suggested there may be a potential risk of standing rainwater percolating through depending on how the ground is falling.

 

[Susana]

Thank you! I will read it. I am going to take another look on a rainy day to see if rainwater sits there. The land there is council owned so I suppose I could ask. I think the ground level looks lower than the ground floor but will also check, Thank you for your help

 

[Cubist]

Based on a preliminary viewing you probably don't know but; are the floorboards laid directly over the concrete slab? Or are they stretched over timber joists that are around 50mm wide and 100-200mm deep? Safe to assume you mean you can see a DPC of some kind in the exterior view of the wall?

 

[Susana]

Yes I can see a dpc on the front wall. I don’t know if there were timber joists above the concrete I’m afraid. Thank you

 

[Susana]

So if there is a concrete base with a clearing between the floorboards and the concrete I could add the air brick in this space, above the existing dpc then I thought we could remove the grey slope outside to allow it all to dry out then see if water pools there. If it does we will add a smaller slope maybe to avoid water pooling there. The French drain idea is a good idea if the council will allow us to do this of course. Do I have to remove the plaster on the inside wall to allow it breath? Could the existing render on the exterior wall be the problem? I can’t see the doc on that way so I am hoping the outside path wasn’t built above the dpc, if this is the case what should we do? As you can see we are novices with regards damp issues so any help is greatly appreciated

 

[Cubist]

Frankly I'd be a little puzzled if there were a concrete slab beneath a suspended wooden floor. That was certainly not common building practice during the Victorian period and would be a very unusual find today. You need to take another look at this house to gain a better understanding of its construction. If you are contemplating purchasing the property you should also consider employing a suitable surveyor before making any kind of binding offer.

 

[a twig]

My parents’ Victorian house has concrete underneath the original suspended floor - suspicion is it was leftover from an extension and was dumped there with the excuse that it would “help with damp” - they at least went as far as levelling it but it only covers around a third of the space