Trench round base of damp walls

[a twig]

Evening all,

I can't remember who it was on here who posted up a great thread about their drainage channel they put around the base of their walls with the natty fibreglass grid over it.

It looks like I'm going to have to do something similar - would whoever it was mind putting up some details of the trenches actual construction? From memory it was cement lined - was there a retaining wall? What were the details of the concrete footings underneath that wall if it existed? How was the wall made? Basically the more technical detail the better please!

I have a week off work next week so hoping to get it done if the weather holds, so will need to order materials soon!

Cheers

 

[Flyfisher]

That would be our stripey friend. This topic will give you something to read until she comes in from roaming the savannah:
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14273

 

[Zebra]

Ah yes. It was me. Iam afraid that although it's technical detail that you're after, my approach to it was not very technical.
I built a french drain, which didn't solve my damp problems indoors. So I was about to rebuild the french drain somhow or other, I can't remember, when my mother said "Why don't you just build a retaining wall and leave it empty?" So we did.
This is the thread where its evolution was discussed, if you'll excuse the many diversions off-topic:
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=12190&hilit=gully
(Look particularly at the final page of that thread...)
So, it was a small independent brick wall - independent from the house's foundations, which are minimal. It sits on a small concrete foundation. Very small. Probably 200mm wide by 100mm deep, adjacent to the house's footings but not attached to them in any way. The wall was modern reclaimed red stock bricks, with cement mortar. The retaining wall does not have any damp proofing or render, it's just brick. The tricky thing was that the ground isn't level, and I wanted to finish flush with the ground rather than level using a spirit level. Also, working inside a trench like that isn't easy.
As for drainage, there is a drain pipe in there which takes away the water from the guttering downpipes on the back of the house, but the rain which actually falls inside the trench simply soaks away into the ground, there is no drainage provision for that. I'm on very free-draining soil.
Building this retaining wall alone didn't solve my damp problems, I had to cut in a dpc; but I wouldn't have been able to do that, or even know that I needed to do that, if it weren't for building this retaining wall first.
Hope that helps. Glad to help with any queries.

 

[Zebra]

This was the thread where we discussed what to cover the gully with. I used fibreglass in the end because it looks OK and is a fraction the cost of cast iron, and less nickable.
http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14035&hilit=gully+cover

 

[malcolm]

I put 3 inches of concrete in the bottom of my trench and built the single brick retaining wall on top of that. The concrete slopes towards a soakaway at one end to drain any heavy rain that falls in. The reason for the concrete was the bottom of the trench might have been at the bottom of foundation level (didn't dig any further to find out) and I wanted to resist sideways movement of the house wall and prevent erosion or movement of the foundations.

The open trench by itself looks to be performing well with interior wall damp levels down from 45% to 15%, though it's summer at the moment and has been very dry which might account for the reduction in damp too.

I've found that willow leaves can get through the grating. Willow leaves can get past anything!

 

[a twig]

Thanks all - very helpful and much appreciated.

I think an exploratory dig to find the foundation depths will be required before I decided whether to concrete the bottom.

Malcolm, I like your sloped approach (although I don't know where I could slope to which would be tricky)!

I shall investigate tomorrow afternoon and hopefully make a start on Saturday - and no doubt be back on here Saturday evening with a whole new set of problems!

EDIT: Just thought - quick question - engineering bricks, bog standard reds or breeze blocks for the retaining wall?