Where is this damp coming from? (with pics) 17 January at 4:13PM in In my home (includes DIY) MoneySaving 45 replies 1.8K views

silvercar

We have a slight damp problem. Years ago cracks in the render were fixed and also a downpipe diverted as we thought that we may have rising damp from the wall near the flower bed. Now the damp is back and we can't find the cause. 

Inside picture shows the effect on the inside of the house (note the walls are solid not cavity). I've marked on the outside picture a cross to mark the spot that is the centre of the damp is showing inside. The down pipe is solid and clear. 



 

plumb1_2

It looks like you have a injected dpc? The ground level is to high, you could start with removing the section of concrete against the brickwork, dig down and fill with gravel, better still if you can put a drain in. And repair mortar joints.

Apodemus

Is the plaster directly onto the brick wall, or do you have lath and plaster?  If there is an unvented air gap behind the plaster, it may simply be condensation from the cold air dropping to the bottom of the void.   

Did you add the fillet of cement between the brick paving and the wall?  I'd guess this was done with good intentions but is (arguably!) more likely to encourage damp than help remove it. 

EmmyLou30

Ground level should be 2 bricks lower than the DPC, and because of the lack of a proper channel drain round the edge a french drain of gravel should be added instead of solid concrete. Not sure if either are responsible for the damp but neither are good practice as it stands. 

Section62

silvercar said:

We have a slight damp problem. Years ago cracks in the render were fixed and also a downpipe diverted as we thought that we may have rising damp from the wall near the flower bed. Now the damp is back and we can't find the cause. 
 

The render/roughcast looks like it is finished flush (or possibly behind) the face of the bricks below.  Rain running down the face of the roughcast could then be soaking into or otherwise penetrating the bricks.  The height is about right (just above) the affected area for this to be a possible cause.

Ideally the render should be finished with a drip bead along the bottom edge so any water drips off well away from the bricks.

In the absence of a formed drip, care would be needed to ensure a DP system is in place so any water is kept out of the brickwork.

When you had the render repaired was anything like that done?

Doozergirl

Section62 said:

silvercar said:

We have a slight damp problem. Years ago cracks in the render were fixed and also a downpipe diverted as we thought that we may have rising damp from the wall near the flower bed. Now the damp is back and we can't find the cause. 
 

The render/roughcast looks like it is finished flush (or possibly behind) the face of the bricks below.  Rain running down the face of the roughcast could then be soaking into or otherwise penetrating the bricks.  The height is about right (just above) the affected area for this to be a possible cause.

Ideally the render should be finished with a drip bead along the bottom edge so any water drips off well away from the bricks.

In the absence of a formed drip, care would be needed to ensure a DP system is in place so any water is kept out of the brickwork.

When you had the render repaired was anything like that done?

Following on from this, there's a visible hole between render and what is effectively now a bit of a plinth formed by the brickwork below, some mortar missing from the bricks of the plinth as well as the open joint. It's ready for water ingress as the brickwork forms a ledge for water to sit and seep back into the house.     

Someone's put flashing band there in the past so it looks like it's been a problem before?  Or is that tape to hold the wires?? 

I'd say either a drip bead above or maybe even some proper flashing that's been cut in beneath the render to be sure?   I can't really make out if the brickwork is sitting proud.   There's some optical illusions going on, I think. 

Re: the DPC comments, I could do with a bit more context on the inside picture - window position would be helpful as I initially thought I was looking at a raised subfloor. 

I agree that whoever has filled in the gap between house and block paving wasn't helping.  It needs to go.  Where is the original DPC? 

Also, where are the wires going into the house?  Anywhere the wries go higher than the hole they go into needs to be looped so water drips away from the hole.  Water will run down and then along with gravity.  

stuart45

If the face brickwork is 9inch, what's above must be less to get the render to come down flush with the bricks. At first I thought it had an oversailing course, but it's the cable that makes it look like that. It could be a cavity wall at the base with snapped headers, which was quite common on 30's houses.

silvercar

Thank you for all your helpful comments.

The render and the first line of bricks sit proud of the remaining bricks, I think this is called oversailing. So the wire is underneath the highest brick row.

I think the plaster inside is solid - it’s a solid wall so no cavity. Wires go all over the place, I should probably remove redundant ones, but I’m always nervous that they do serve some purpose.

that tape was some sort of sealant I think, it isn’t holding any wires.

The bottom picture shows some cemented holes near ground level on the left hand side, I’m guessing that is a dpc, that someone put in at some point in the past. Solid floors inside, solid walls, so no air gaps anywhere.

Apodemus

silvercar said:

The bottom picture shows some cemented holes near ground level on the left hand side, I’m guessing that is a dpc, that someone put in at some point in the past. Solid floors inside, solid walls, so no air gaps anywhere.

Ah yes, I see that now!  The infamous row of drilled holes where some charlattan injected some meaningless gunk!  

Norman_Castle

Doozergirl said:

Section62 said:

silvercar said:

We have a slight damp problem. Years ago cracks in the render were fixed and also a downpipe diverted as we thought that we may have rising damp from the wall near the flower bed. Now the damp is back and we can't find the cause. 
 

The render/roughcast looks like it is finished flush (or possibly behind) the face of the bricks below.  Rain running down the face of the roughcast could then be soaking into or otherwise penetrating the bricks.  The height is about right (just above) the affected area for this to be a possible cause.

Ideally the render should be finished with a drip bead along the bottom edge so any water drips off well away from the bricks.

In the absence of a formed drip, care would be needed to ensure a DP system is in place so any water is kept out of the brickwork.

When you had the render repaired was anything like that done?

Following on from this, there's a visible hole between render and what is effectively now a bit of a plinth formed by the brickwork below, some mortar missing from the bricks of the plinth as well as the open joint. It's ready for water ingress as the brickwork forms a ledge for water to sit and seep back into the house.    

I'd suspect as above. I had a leak through a gap where render had been patched on a solid wall. The damp patch on the inside looked very similar to yours. I filled it with exterior filler, problem solved. I've always assumed rising damp would cause a vaguer damp area.

diystarter7

markin said:

I found the source of your tripping power!

Exactly what I thought when I asked if that was a damp patch I could see on OP's other thread.

These damp treatments are often nt that great and do break down. IMO its a combination of poor dampproof work and possibly a bit of repair outside

OP, FYI, I am no expert in this areas but vast knowledge of owning, looking after our properties, doing them up, helping the kids etc have given some ideas and times these ideas do help me and my family/friends et.

Thanks