Been reading this site for some time now, and decided it was time to post. I have recently moved into a Victorian house which has high external ground levels which are up to the DPC. I have some minor damp problems inside so want to reduce the ground levels to try and alleviate the damp.
The photo below shows what the situation is. The gravel area against the house is probably only 10mm deep gravel, sitting on some sort of membrane (I assume to keep weeds from growing) and beneath that is just soil). The gas pipe you can see running along the ground sits right along the mortar joint with the old DPC. All the mortar had fallen out, so have recently had the pipe moved up and the joint repointed. I don't think whats left of the DPC will be doing very much.
The photo below shows what was a raised rockery by the back door (opposite the front of the blue car in the first photo). This is definately above the DPC, so have already pulled this down. I think this was originally raised to stop rain running down towards the side of the house - which slopes down and the internal floor levels are lower than the rest of the house (you can just see the corner of the back door in the photo at a lower level).
You can see below after I have lowered the rockery slightly and also see how the back door and beyond is at a lower level, so something else I need to keep in mind with any work I do.
So to the point of my post - can anyone give any advice on the best method of reducing the ground level against the house without having to completely relay the patio?
If I was to dig down the whole soil section against the house, could I just lay gravel and not drain away to a gulley? I'm a bit concerned with rain water running straight down into the foundations, but surely that is no different to what is happening now?
I was thinking about the dry area arrangement but not sure how I could incorporate that without redoing the whole patio area.
this is very common with older properties
the path i dug out last week had block paving,on top of pcc slabs ,on top of yorkstone paving
obviously over the years different people have added rather than do it properly and take stuff out
the answer you need is on this page
however only you and your contractor can decide the course to follow
I am not a big fan of gravel traps and would rather the water went somewhere,I.E> a soakaway or a combined sewer
cheers LLL
The page to which LLL refers you contains detail of the most popular workarounds, but as he says, gravel traps are less than ideal. It would be much better to use a linear channel against the masonry and have that linked to an outdfall, maybe one of the rain water pick-ups?
However, I suspect you know that the only real fix is lots of digging and complete re-construction of the paving.
Think about it: you can put in a good weekend's work to install a linear channel and hope it helps, or you can give over a couple of weekends and get the whole lot droppped to a more sensible level, and then sit back safe in the knowledge that it's a job you won't have to do ever again.
Thanks for the replies. Been reading that DPC link many times over the last few weeks, I guess I was hoping for a quick fix which wasn't listed on there!
Eventually I will competely redo the patio and ensure proper drainage and correct ground levels, but think that may be a good 18 months away as I have other parts of the hosue I need to do up first. I was hoping to do some sort of medium-term fix that allowed me to reduce the ground level against the wall immediately to allow the internal walls to dry out (hopefully) and then follow up with a new patio and drainage at a later date.
If I just reduced the ground level at the house and ensure there was a slight incline towards the patio area, is water draining away through the soil likely to affect the foundations adversely?
The other slight concern would be that if I reduced the soil level to the paved area that it might destabilise the paving - I do sometimes park the car on it and it is already falling apart. I suppose I already know the answer to that...
Get a man and digger in for a day maybe 2 and have the lot dug lower. Maybe 400-600 in total to dig out and remove the spoil. Then you can start to consider new surfaces. I can see looking at what has been done previously that none of it is worth trying to save anyway
Also meant to mentioned I'm a bit concerned with digging down to reduce the ground level as I have a feeling the foundations may be very shallow. When I reduced the raised bed area the footings didn't seem to go down more than two courses (although I didn't poke around too much to make sure). There is a photo below showing my handywork. I would be worried that if I dug down to lay concrete to reduce ground levels then I could de-stabilise the house itself.
Has anyone come across shallow foundations like this on a Victorian house?
Maybe the ground levels were always meant to be this high due to foundations - does anyone have any experience with Victorian houses and normal ground levels?
That looks ridiculously shallow. You'd do no real harm digging down another 300mm or so to find out whether that really is a bottom or whether there's summat more beneath.
A small trial pit just a spade width is normal when investigating foundations, and as long as it's backfilled, there's no risk.
Took your advice and dug a small pit to check out the foundations a bit better, about 100mm to the left from the previous photo location.
It seems the foundations go down further than I thought, photos below. The first brick course (the first step out) is 100mm deep, followed by a larger brick 180mm deep. There then does seem to be another brick below this but I didn't dig down any further to find out and it seems to get a bit wonky.
I think my plan will be to reduce the ground level against the house down to the mortar join between the first and second bricks, this will make the ground level about 120mm below the DPC. Only things I'm not 100% sure on is whether to put a linear drain right up against the house wall, or have some paving against the wall sloping away sharply, with the linear drain around 300mm from the house.
Any thoughts? I should point out this face of the house faces south-west so gets a lot of rain driving against it when it rains. Appreciate any more advice
Yep you got it right where the DPC is in your diagram - about level with existing ground level. Based on your diagram, I think I will pave to the first mortar joint (120mm below DPC) with a steep fall mainly because I want to avoid going any deeper in the foundations than I have to. I was then planning to put in a linear drain say a brick length away from the wall - does that sound about right?
