Foundations, high ground and slate

[MatthewC]

I have an obvious damp problem with some ground along the side of my house which is higher than the tiled floor inside by about six inches. There is a concrete path about 20 inches away from the house wall (limestone rubble), and between the path and the wall is soil, which I have lowered by about six inches as a starter. Logically the original level of the ground was below the floor level by some way, so I reckon that the wall must continue far enough down to allow me to remove the soil and restore the ground level to somewhere below the floor level.

Today I tried to remove a shrub growing beside the wall*. Digging down beside the roots, I found lots of small limestone rocks and some slate, and about six inches below the floor level there are some flat, level rocks which I would guess indicate the start of the foundations so I haven't gone any further.

However, to the side of the roots I also found some slate which appears to have been carefully laid. It is two pieces of overlapping slate, parallel to the wall, which slope down away from the wall at about 45 degrees, starting at about 2 or 3 inches below the floor level, and ending just above the level of the "foundation" stones further along. I reckon the other slate I found was similarly placed but was mucked up by the roots (or my digging).

Question: Given that the slate appears to be deliberately placed as some sort of aid to drainage, is this use of slate usual?

If so, then I would think that it must confirm that the level of the top of the foundations as well, and so I can dig down to that level, can't I? (The house was built post 1830 as a school and had substantial modifications in the mid-1800s to be a pair of semis, and I think this bit is later.)

All constructive comments gratefully received. I would do a drawing but I'm not feeling artistic tonight...

Matthew
http://houseintheenchantedforest.blogspot.com/


* Outside, of course - The house is not that bad!

 

[Lime]

The slates may have been placed to deflect the shrub roots.
What are you expecting to find if you dig further down next to the wall?
I often read on this forum mention of "foundations" but it is a fact that most old houses do not have them, absolutely nothing.
The house wall in the ground may enlarge slightly (perhaps a brick width or more) but directly under that enlargement the wall stands on subsoil.

 

[MdB]

The house wall in the ground may enlarge slightly (perhaps a brick width or more) but directly under that enlargement the wall stands on subsoil.

If you are lucky. If you are not then you will find that the base stones are on top soil rather than subsoil. I do so love Cornish builders... (even 19th Century ones)

 

[middi]

It is quite common to have slate DPC integrated in the footings of brick built houses of that age. Provided that the slate goes right through the depth of wall and overlapped it would serve as an excellent DPC.
It is my guess that the external floor level has got higher than the internal over the decades. I don't think you will have any problem lowering the external, by at least 200mm, in relation to the interior. If the slates are laying at an agle against the external wall it proves that someone has put them there as an afterthought in the hope that the raised external soil level would have been isolated from the lower foundation wall. It would have been a waste of time.
It appears that you have some external soil to remove :wink:

Middi

 

[Lime]

Following on from middi's comment, if there is slate protruding from a course of mortar between the bricks around the house that needs to be uncovered/exposed.
However I gained the impression that the slates mentioned were just leaning against the wall footings.

 

[Penners]

If the slates are laying at an agle against the external wall it proves that someone has put them there as an afterthought in the hope that the raised external soil level would have been isolated from the lower foundation wall.

That was my first thought, too. If that section of the wall is damp, then there's every possibility that the slate was inserted to try (unsuccessfully, unsurprisingly!) to keep the damp soil away from the wall.

 

[AMc]

I found some slate laid vertically between the wall and the top soil on the side of our house. My guess was it was an attempt to stop roots growing into the wall rather than a damp proofing measure - I wish they hadn't built a brick plinth against the wall and planted a passion flower through it - beautiful and fruitful but growing in an untraceable hole right by the walls. As I can't kill it by pruning it back to the ground I dread to think where its roots may be...

 

[Moo]

As I can't kill it by pruning it back to the ground

Does that mean that you can't bring yourself to do the deed, or you don't think that just cutting it to ground level would kill it off?

 

[Penners]

It's a well-known fact that plants you want to kill become miraculously immortal. Whereas your treasured specimens will turn their toes up at the merest hint of a cross word.

 

[middi]

Remember " THE DAY OF THE TRIFFIDS" ?

Kill it !!!!!.

Middi

 

[MatthewC]

Thanks for the advice so far. Here's a photo which I took today (having forgotten my camera yesterday), after a bit more exploration:

The current ground level is at the top of the picture; the floor level inside is at the horizontal scratch on the second stone down on the left; the possible foundation level is at the base of the third stone down, represented by the flat stone between the two pieces of root. The overlapping pieces of slate (which slope away from the wall at 45 degrees) are on the right, and other pieces were found between the roots.

I'm sure that the ground level rose particularly when someone installed the concrete path alongside the house; on the other side of the path the ground level is already two inches above the path, so possibly they were trying to hold back the natural rising ground.

I acknowledge that there is often no actual foundation on this age of building, and that there may or may not be anything below the flat stone in the centre. However, to alleviate the damp I need to go down at least as far as the top of the slate if not further, and I don't really want to explore down any more! I'll see if there is more slate down there but I see no real point in keeping it as it clearly only adds to dampness.

 

[Feltwell]

It's a well-known fact that plants you want to kill become miraculously immortal. Whereas your treasured specimens will turn their toes up at the merest hint of a cross word.

Very, very true. When we moved in the whole of the back of the house was covered in Virgina Creeper - and the damn thing refuses to die, despite being cut back to the ground and treated with several almost certainly deeply environmentally unfriendly substances.

Still, I did manage to kill my Russian Vine (known by some as mile-a-minute, with good reason). Digging it out with a 5 ton digger then building a garage on top of it seems to have done the trick!! Now, I just need to get rid of the bindweed.......

Matthew, my neighbours house has roof slates stuck on with cement mortar (of course) round the base of part of their wall, as a bodged damp proofing measure against a high external ground level. Totally useless, especially as it bridges the original slate DPC in the wall. The section in question is against my land - when I built my garage, we dug out against his wall to lower the ground level to around 9 " below his slate DPC. 12 months on and he tells me the previously very damp wall is drying out nicely, even though it's covered in cement based render from 3' up.

 

[Flyfisher]

Still, I did manage to kill my Russian Vine (known by some as mile-a-minute, with good reason). Digging it out with a 5 ton digger then building a garage on top of it seems to have done the trick!!

Careful! As I recall, your rather impressive garage is not all that old. That vine could just be building up its strength ready for the day you awake one morning to find you have a new tree house. :wink:

 

[Penners]

:lol: :lol: :lol:

 

[Lime]

I'm sure that the ground level rose particularly when someone installed the concrete path alongside the house; on the other side of the path the ground level is already two inches above the path, so possibly they were trying to hold back the natural rising ground.

I acknowledge that there is often no actual foundation on this age of building, and that there may or may not be anything below the flat stone in the centre. However, to alleviate the damp I need to go down at least as far as the top of the slate if not further, and I don't really want to explore down any more! I'll see if there is more slate down there but I see no real point in keeping it as it clearly only adds to dampness.

I'd take the level down to the top of the flat stone.
As you suggest, I'd remove the slates.

 

[Moo]

Now, I just need to get rid of the bindweed.......

No problem there. Just flatter the plant into believing that you want to turn it into an ornamental feature in your garden.
Provide it with some strategically-positioned supports and encourage it to climb.
When it is looking really healthy, unwind it from the supports, immerse it in a bucket of systemic weedkiller and forget about it. Give it plenty of time to suck the poison deep into its roots.
Job done.

 

[AMc]

As I can't kill it by pruning it back to the ground

Does that mean that you can't bring yourself to do the deed, or you don't think that just cutting it to ground level would kill it off?

I chopped it at the point where it emerges between the paving slabs and it still recovered in less than a year, flowered and fruited.
I'd love it much more if it weren't potentially under the foundations but it doesn't seem to have brick attacking tendrils so I've decided to live with it. esp. after seeing test pits for the foundations a couple of years back that show they go down at least 6 feet under the soil.

We also have bindweed which I've been fighting a valiant battle with for several years. The problem is it's quite simple to remove most of a length of the plant but it will regrow from the smallest fragment of root (as evidenced by the bits pulled up the next time). Even paint on herbicides which I don't want to use will only kill a little bit of it. It grows like a so and so merrily finding its way 8m along the new dwarf wall of the vinery in a few months despite being completely removed.

 

[Penners]

AMc - here's a suggestion. Chop any new growth back to the woody trunks that you show in your photo. Drill several holes vertically downwards into the tops of the trunks and fill them with a strong mix of glyphosate weedkiller. For family safety, plug the tops of the holes or wrap with duct tape.

I've used this technique to kill stumps and it's worked every time for me.

 

[Moo]

Even paint on herbicides which I don't want to use will only kill a little bit of it.

Not if you drown an eight-foot length of the stuff in a bucket of glyphosphate, allowing plenty of time for it to travel right down to the roots.

 

[Feltwell]

No problem there. Just flatter the plant into believing that you want to turn it into an ornamental feature in your garden.
Provide it with some strategically-positioned supports and encourage it to climb.
When it is looking really healthy, unwind it from the supports, immerse it in a bucket of systemic weedkiller and forget about it. Give it plenty of time to suck the poison deep into its roots.
Job done.

Good idea Moo - That does sound like probably the only way to get rid of the damned stuff, even though I'm not a big fan of using chemicals in the garden. I'll have to find some way of ensuring that Les Enfants Terribles are kept away from it.

Most of my bindweed is in the lawn now, which is far from a bowling green - so it just gets mowed. But it does spread and I think one of my hedges is probably full of it by now.