Damp coming through concrete block retaining wall

brianhickey

My garden backs up more houses at the rear, and their garden is about 1M above ours. There’s a lot of moisture coming through the wall where it is below ground on their side, I’m wondering is this going to be a problem?

10-10-20

When was that wall built and when did the water start to seep through like that? Is it isolated to a patch or is it relatively consitant along the wall, as far as you can tell? Also what part of the country are you in?

I'm wondering that it's a new phenomenon, it might be an indication of a mains leak or even something seasonal like a spring or even just the 'normal' water table.

Vestiapx

It's been quite wet this month

10-10-20

It has and there are indications that the issue has been ongoing for some time by the way that the salts/calcium deposits have started to harden. A recent change to the land up-hill from this point may have had a bearing.

brianhickey

The wall is 9-10 years old. It’s not a recent thing, it’s been consistent since the start of guess but I only noticed a couple of years ago.

It’ll fail eventually but I’m wondering if it’ll be anytime soon. It was a new build & we are coming up to our 10 year guarantee so trying to decide if it’s worth chasing the developers over.

Mellor

https://www.boards.ie/discussion/comment/122553759#Comment_122553759

Blocks aren't waterproof. Any block retaining wall will let moisture to bleed through.

If it was an internal wall it would be tanked, but being a garden wall there's no requirement. I wouldn't fancy your chances chasing a warranty on this.

brianhickey

https://www.boards.ie/discussion/comment/122554685#Comment_122554685

I’m no expert but looking up online there’s things they could have done, some sort of lining or coating on the far side would cut down a lot of it.

Anyway I’m not that upset about it, unless it’s going to collapse in the foreseeable future.

My plan is to clad it in treated timber (with waterproof tape where it touches the wall), as I feel like paint will not hold up very long with all the moisture coming through. I don’t want to go to all the hassle of that if the thing needs to be replaced in the next 5-10 years.

bfclancy2

https://www.boards.ie/discussion/comment/122553759#Comment_122553759

its not going to fail, where are you getting this notion from, its purpose is to retain soil not water

10-10-20

The critical part is laid 'block on flats', so it's not going to move all that readily anyway.

brianhickey

https://www.boards.ie/discussion/comment/122555313#Comment_122555313

Water destroys everything given a long enough timeline. I’m not expecting it to be impermeable I just wanted some reassurance that what’s happening is within tolerances.

bfclancy2

https://www.boards.ie/discussion/comment/122555781#Comment_122555781

every wall in the country is the same as yours it'll be there long after you

Mellor

https://www.boards.ie/discussion/comment/122555312#Comment_122555312

The coating is the tanking I mentioned. They could have applied it, but it’s expensive and of little benefit when the wall is exposed to weather on both sides.

similarly, I would not bother with water proof tape under the timber. They’re be exposed to far more water from the rain

brianhickey

Thanks all!

https://www.boards.ie/discussion/comment/122557405#Comment_122557405

My thinking with the waterproof tape is, the timber that isn’t touching the wall has a chance to dry out from the air, whereas the part touching the wall is just going to get a continuous flow of moisture with nowhere for it to go. I put up some lengths as a test and they were all damp to the touch on the wallside when I took them down.

10-10-20

A piece of visqueen/DPM at the back of the vertical supports will prevent the water from tracking across and I believe that it will prolong the life of the cladding. As long as there is room for air flow behind the cladding then, it should dry off fine.

Lumen

Retaining walls should have weep holes to relieve hydrostatic pressure.

You absolutely do not want to retain water behind it. You want water coming through the wall in a controlled way. A bit like vents are used in buildings to control air movement.

Mellor

https://www.boards.ie/discussion/comment/122559722#Comment_122559722

Of course, water is dense. Retaining it creates work.
But water weeping though a wall, means the wall will be damp. Other than moss/algae growth. This shouldn't be an issue