Penetrating damp

[jacdaniels]

Hi all,
I have a victorian house with a ground floor lower than the external street level. I have a damp wall which I believe is due to this. On digging out a concrete section level to the damp on the outside, I found it to be very damp, (there was plastic sheeting below the concrete where water had pooled). I want to remove the plastic sheeting and concrete and replace with something that will fix the internal problem.
Will digging down deeper, (below the internal floor level), filling the hole with some sort of drainage ballast and re-concreting over the top solve the problem or can anyone help with another solution? The damp is about half way down the side of the house which is an external wall directly on to a downward sloping street/pavement.

 

[JerryM]

i feel a combination of actions are probably going to be needed. having grd floors below street level is not good.

1st you need to divert the water away from the wall. i think your idea of digging out and filling with ballast is good. it's important that the trench can drain at one end at least ie onto a lower ground level (sloping street/pavement). i would also put dpm sheeting in an "L" against the wall and on the base of the trench so that it is sandwiched between the wall and ballast. i would not re concrete as you need to get a fall away from the house which is difficult with concrete (tendency to self level).

flags would be a better method but ballast channel would need to be kept narrow so flags have sturdy ground to be laid on.

2nd as a precaution i would also go to local builders merchant to see what's available for sealing the brickwork below ground (in case small amounts of water get between wall and dpm sheet). i've use bitumen inside before successfully.

 

[jacdaniels]

Thanks for the advice.
I have indeed removed the major source of the water, which was a gutter downpipe, and I'll certainly put DPC sheeting in the channel. When you say use Bitumen as a waterprrof layer, do you mean I should paint it on the outside brickwork, in the channel, (i.e. below ground level before I use DPC and fill with ballast)?

 

[jacdaniels]

Sorry, I mean't DPM sheeting not DPC.

 

[JerryM]

i've not had the exact situation as in past have either sorted via flags having a decent fall or tanking on the inside as part of full damp proofing. i do use the paint on dpm bitumen inside and it works well.

i don't know what is best for outside though hence the suggestion to visit nearest builders merchants and ask what's best (used a lot).

the plastic dpm sheet, ballast and drainage outlet at the end of the channel will be a big improvement and may just sort it. you may want to try it and see particularly as the down pipe is now fixed (and would have been a major factor).

the paint on dpm below ground on the brickwork in the channel is a further precaution. my thought being that whilst the channel is open it would be relatively quick to paint on and not too costly. the trouble is we just don't know for sure if it's needed. suggest wait and see a few weeks to see what effect the down pipe repair have.

the other thought i had was to create an air gap to the wall by fixing slabs in concrete in the channel to form a sort of retaining wall. trouble with this is that debris can over time fall into the cavity and therefore not my preferred approach.

 

[jacdaniels]

I think I'll try a bitumen type paint as it can't hurt. I'll leave the channel open to dry for a few months then do the work. At least it sounds like I'm heading in the right direction.

Thanks again for all the help.

 

[JohnD]

repoint the brick if they need it, while you have it open. lime mortar in particular erodes in wet ground.

 

[JerryM]

would endorse JohnD's comment on the repointing. The joints are crucial in keeping the water out and repointing should be the 1st course of action.