Possible Cause to Damp at Bottom of External Wall

[Holly64]

Wall is solid, no cavity, yellow stock brick - circa 1930s.

Have noticed this damp point on the base of wall. On close inspection, I can see missing mortar in several places and also some cracks going through the bricks. I had a poke about and some of gaps where the mortar is missing is very sandy. Poke it with finger and it practically dissolves! It is just this one area on the whole of the property.

Could the cracks and missing mortar be the cause of this damp patch?

I assume I need to get a builder in to rake out and repoint?

Can this be done whilst the bricks are still damp?

If so, can a water repellant be painted on the brick work after repointing?

 

[JohnD]

Quite likely you have had a water leak.

Your house looks quite old and has yellow stock bricks, possibly hand made, as used to be made of Thames mud. When there are fragments of lime or chalk in them, they expand and burst out when, after firing, they get wet and expand. I think I can see such pockmarks.

Lime mortar is softened and washed away by long term leaks. I mostly see it beneath the ground where a pipe or drain has been leaking unseen, leaks above ground are more often noticed and repaired.

Clay gullies and drains are usually cracked or broken.

Depending where you are, a leak can turn the ground to mud and wash it away. Old houses often have shallow foundations and if the ground beneath them is washed away, leaving a cavity or a pool of wet mud, the wall will subside into it.

Perhaps I am wrong and these signs have some other cause. But I do see pipes near your problem area. And some damp and green patches on your bricks, conspicuously close to the gulley. Can you find the DPC?

It is a pity that concrete has been laid to conceal (but not repair) what lies beneath. It may also bridge or cover the DPC.

Do not allow anybody who sells silicone injections near your house. They do not repair broken drains or leaking pipes.

Take some more pics around that clay gulley, please, and a wider pic showing the entire wall and the ground or concrete at its base, and indoors showing the plumbing and the damp.

 

[JohnD]

Could the cracks and missing mortar be the cause of this damp patch?

No, but the reverse is likely.

Water repellent will not repair the source of water.

 

[^woody^]

Brick walls are porous with and without cracks.

Next time it rains have a look at how much water is dripping off that cill onto the path, or running down the wall below the cill.

 

[JohnD]

Just above the concrete, I think that is the remains of an old cement plinth peeping out.

These were usually applied to damp walls to hide (they do not cure) damp. The original DPC is probably behind it, and bridged by the plinth.

The fact that it is mostly covered by the new concrete paving means that the ground level has been raised and is probably now above this DPC. This enables damp to soak into the lower bricks.

IMO the source of the water is the gulley and other defective plumbing. It will probably become apparent when you dig out the gulley to replace it and repair the wall. This is a common job, and not complicated, but there will be extra effort in removing the concrete.

If the effort and expense of removing it all and reinstating the original ground level is too great, a slightly smaller job is to excavate a trench against the house. You can fill it with cobbles or large pebbles so you don't fall into it. Not shingle. The larger stones have large irregular gaps between them which prevents water rising by capillarity, and are very free draining.

The gulley and other defects need to be dug out anyway.

 

[Holly64]

Thanks for all replies.

I'm not about for a few days to take any more pics. The clay gulley is definitely damaged. The property is a bungalow and there was a leaking gutter immediately above the damp patch. This has now been sorted.

It has definitely been raining hard and constant for a while. The DC is visible - its slate but it might be damaged in this section.

My dad has owned the property for 14 years and the walkway/path was in place.

Hopefully better pics will help in a few days then I just need to find a builder to resolve.

I'm just trying to get as much of an understanding before getting in a builder and possibly fobbed off with incorrect solutions. We would have fallen for the silicone injection

 

[JohnD]

Can you show some pics of the DPC? It will be at the same level all round the house.

Slate lasts hundreds of millions of years and does not wear out.

 

[JohnD]

My dad has owned the property for 14 years and the walkway/path was in place.

The damp, and erosion of lime mortar, has been going on much longer.

 

[Holly64]

Thanks, I will get more pics in a few days and post then. The rest of the bungalow is fine - walls all dry but I will take pics.

 

[ree]

Holly 64,
You have poor re-pointing and porous original pointing in a solid wall - conditions that might be contributing to the interior damp. Can you post pics of the interior damp?
Rake out to 25mm depth, and re-point with a sand & NH lime 3:1 mix.
The crack is no big deal unless the wall is mirror cracked inside? Its claimed that cracks below windows are a result of thermal expansion. They can be filled with polysulphide from a gun cartridge.
I cant see a DPC - try and find the mortar bed with the DPC, & perhaps point it out on a pic?
There's a sand & cement fillet where the path abuts the house - remove it.
The gully looks rough and could do with replacing - can you take a pic from above the gully?
The patch of mortar smeared brickwork above the gully - why not replace those bricks, while renewing the gully, to make it look decent?

 

[JohnD]

There's a sand & cement fillet where the path abuts the house - remove it.

That's the thing that looks to me like the visible part of a cement plinth.