Exterior drain problem

[anotherdaveuk]

Hello,

New to this forum, so hope this is the best place for this post. (Please let me know if another would be better!)

I've had a problem with our outside drain, visible on these two pictures:

http://yoyo.org/~den/img/lansdowne/IMAG0035.jpg

http://yoyo.org/~den/img/lansdowne/IMAG0033.jpg

You can see that (a) there is a hole down the side of the drain just behind the grid cover, meaning that waste water was going straight into the ground/foundations and (b) the render on the left hand wall is damp and coming away.

Now, we've just had some work done on this drain (along with some other work) but I'm not sure about some aspects of it. Here are links to the "after" pictures:

http://yoyo.org/~den/img/lansdowne/IMAG0021.jpg

In the above, you can see that the drain is blocked (probably with material from the repointing we had done at the same time). However, the concrete surround has been installed so that I can no longer remove either the pipes or the grid cover in order to unblock it!

http://yoyo.org/~den/img/lansdowne/IMAG0022.jpg

http://yoyo.org/~den/img/lansdowne/IMAG0020.jpg

In the above 2 pictures, you can see the damaged render has been removed and you can see the slate damp proof course. There is also still a hole at the top of the picture meaning that any overflow waste water will STILL be draining into the foundations. And, of course, if there is heavy rainfall or if we run a bath, then the water will almost certainly rise above the level of the DPC.

The interior side of this wall DOES suffer damp, which was the problem we were trying to sort in the first place. I'm not sure this isn't worse than before...

Any advice on how best to proceed from here? The people who did the work are coming back today to take a look.

 

[Hugh Jaleak]

The blue bricks could well be the DPC, so the gulley is well below that level, however the quality of the benching around the gulley is rather appalling.... Needs to be a reasonably strong sand/cement or Grano mix, by the colour of that, the cement content is rather low. Gaps at edges of gulley surround could do with filling in, just makes for a neat finish to the job IMHO.

Benching needs sorting so grid can be lifted, then the gulley needs cleaning out completely so the water can drain. Its possible the builders have dropped crud on top of an existing build up of rubbish in the bottom of the gulley. (Leaf mould, soap, fat etc. it all needs removing. Decent pair of rubber gloves needed!) The waste pipes could be altered to discharge below the grid, then benching redone to fill the holes and guide the water where it should go. Sometimes a piece of slate was fixed vertically to the wall to provide a 'splashback' and prevent water penetrating the masonry.

Possible the DPC has failed, or the render is bridging the DPC externally, but from the pictures it seems unlikely any splashback from the existing arrangement would cause a major problem, the issue is most likely rising damp.

 

[anotherdaveuk]

Thanks, Hugh, for the reply.

The bricks do look blue in that picture but I don't think they actually are or are the DPC. (Oddly, this terrace is the only one for miles around not built from yellow stocks, but I'm not sure what colour they really come up under the 115 years of dirt!) You can see a sliver of slate just above the bend in the grey pipe, and so I think that's the slate DPC.

The benching and grid and pipework have all been redone now, pretty much exactly as you describe (despite knowing the square root of bugger all about this kind of thing, I thought the colour of the benching suggested an odd mixture too) and there was indeed a load of rubble down there (not all from this work either by any means).

The slate is an interesting idea - I might do just that - and put one behind the garden tap further along the same wall too while I'm at it.

As for damp, I'm trying to eliminate everything except plain rising damp by getting all this work done. All the render has been removed now and the French drain fitted. There was also a big gap between the double glazing and window frame where the rain got in, but I've fixed that too now. It was suggested I might bitumen paint the bottom few rows of bricks, but online searching suggests this is a bad idea. I'll certainly give this work a good few months to bed down and dry out and see what happens before doing anything more.

Thanks again - nice to just have a second pair of eyes when I've not had anything like this done before.

 

[Hugh Jaleak]

I've got a Victorian property so I know exactly where you're at with damp! Thompsons Water seal is an idea, I wasn't sure about using it, but the Building Inspector suggested it when he came round about another matter. Problem I have is the Council has successively raised the height of the pavement over the years, its now borderline on the DPC at the front. Penetrating damp is an issue the the front wall of the house.

The Thompsons has seemed to make a difference, but make sure the wall has had chance to dry out after a spell of warm weather (assuming we'll get some this year...), otherwise you can seal the damp in the wall.....

It's also possible the iron rainwater pipe was leaking, appears thats been replaced so rules that out too. Fingers crossed you'll see an improvement now.

 

[anotherdaveuk]

Excellent, thanks - will give that Thompson's a go later in the summer.

I was also thinking about improving the French drain now the hard part's been done and use a membrane liner along the wall down there but, again, we'll see in a few months!

 

[Nige F]

Thompsons is exellent - I had water leaking down my chimney round the pot/flaunching - poured half a gallon of Thompsons round it ( slowly) 2 coats - job done lasted over winter no bother - re flaunch it this summer