Do we need an engineer?

[FamilyWiggs]

Two and a half walls of our dining room are below ground level. The house wasn't built like this, but at some point the yard above was created by filling into ceiling height on 2 sides. This is causing some problems with water traveling through the stone walls and through the lime plaster - leading to mould behind pictures and puddles on the floor after prolonged periods of very heavy rain.

It's time to do something.

We think the answer is to dig out down to the original floor level, put in a gulley at the bottom and create a retaining wall leaving a gap of some 3 feet between the new retaining wall and the original external wall.

I've dug a small test hole, and think the infill is primarily rubble and a lot of what seems to be coke and some slag/molten metal. I'm hopeful of finding an original retaining wall when I excavate, as well as the original cobbles I'm told were there before the concrete yard floor.

Do we need a structural engineer to advise on the state of the walls and how to proceed, given they would presumably have been under considerable lateral pressure for decades? SWMBO is concerned about collapse once the infill is removed. The walls are approx 2 foot thick sandstone. They looked fine internally before we removed the 70's polythene tanking and lime plastered.

I'm more inclined to hire a big digger, take up the concrete yard and start digging.

Advice gratefully received.

Robin

 

[Flyfisher]

If the house was originally 'free-standing' then, presumably, it was all structurally sound at some stage. Piling stuff up against the walls up to the first storey would have, again presumably, exerted a fair force against those walls. But since the walls have resisted that force for all these years, I can't really see why they'd suddenly become unstable if all the stuff piled against them were removed. That would imply that the walls were somehow 'pushing against' all that stuff and would therefore fall/bulge outwards when it was removed. I can't imagine how that could happen - but then I'm not burdened with the knowledge and understanding of a structural engineer!

As for a retaining wall for the remaining 'stuff', is it not possible just to slope it away from the house, thus avoiding the need for a retaining wall at all? Or, if you decide you do need a retaining wall, you could work on the principle that a 2-foot thick sandstone wall (of your house) seems to have done a good job up to now, though I've no idea about the degree of overkill involved.

Perhaps another way of looking at this would be to consider your home insurance position should any problems arise due to some fairly extensive groundworks that have not been approved by a structural engineer? How much would it cost for an engineer's appraisal anyway?

 

[JoceAndChris]

Gosh Robin how exciting ! ( though puddles do sound lots and lots of fun for your boys, and you could bring your poor remaining goose inside).

But I'm with SWMBO. Women need lots if advice and reassurance from men in hard hats, no matter the technical capabilities of our husbands. It's not a small thing, your proposal, and caution says it would be wise to have a professional opinion before proceeding.

Then, if anything does go a bit pear shaped, you can be absolved from blame.

 

[worms]

I've no expertise on this but I think I would be more concerned about the weight of material uphill than the house wall itself and would advise real caution about getting between the excavation and the house wall in case the remaining infill moves.

 

[FamilyWiggs]

Thanks for the comments so far.

FF - you're thinking much the same as me, but Joce is right that professional advice should be sought. I doubt however it will absolve me from the blame if half the mountain ends up in our dining room! SWMBO would still consider it all my fault.

Not really an option to have a sloping surface, as the ground above is our yard/car park and is only about 20 feet wide before you come to the outbuildings, which are just to the right of this picture.

Worms' advice is very sensible. I hadn't intended to dig out by hand :shock: , but with a digger. And presumably one digs out too much, builds the wall and then infills behind? But yes, I suppose it is potentially dangerous.

Anyone any idea what a report is likely to cost from a reputable surveyor? At the same time I'm going to ask him to look at the front wall of the outbuilding which is bowing out very considerably now, and not tied into internal walls. I'd like advice on the scale of risk, and remedial actions I need to take. I think the roof (which is fine) needs to be supported, then the wall needs to come down and be rebuilt back up and tied in as appropriate. Some of the internal stone wall will probably need rebuilding too. I'll try and post a pic of that if the Welsh sunshine would ease off a little today.

 

[Penners]

since the walls have resisted that force for all these years, I can't really see why they'd suddenly become unstable if all the stuff piled against them were removed.....but then I'm not burdened with the knowledge and understanding of a structural engineer!

I agree with FF - with the same rider about my technical competence (or lack of)! If the lateral pressure on the wall hasn't caused it any problems, then I can't see how removing that pressure would do so. Given that the wall was originally constructed to withstand largely vertical loadings, then I can't see how restoring that that situation would affect it in any way, other than beneficially.

 

[Flyfisher]

Well, they say that pictures are worth a thousand words and that one certainly shows the scale of the matter!

Is it just the bit of land between the house and the 'road' (below the blue toy?) you're planning to remove? Is the 'road' yours or does it belong to someone else? I don't know what happens if you remove a part of your land which then causes part of someone else's land to collapse, but I would guess that you'd be responsible. I wonder if this is similar to a 'party wall' situation?

Hmm. I guess I'm not helping much with all these questions but, having now seen the scale of the thing, I think I'd be seeking some sort of professional advice before rushing in with a digger (good call Joce - a cool head in the face of some gung-ho boys!). I still reckon it should be possible to do what you're planning though and I'm sure it would be good for the house. Perhaps ask a couple of building contractors to come out and advise/quote for the job and see what they make of it?

Also, I bow to no-one in my enthusiasm to play with some big-boys-toys but I don't think I'd want to operate a large powerful digger in such a confined space so close to my house.

 

[FamilyWiggs]

Yes - we own all the land, including the stone outbuildings you can't see on the right of the picture, so no probs about access, etc.

We're thinking of excavationg the front wall you can see, the wall with the blue toy and door and about 10 feet round the back that you can't see.

I've done some digger work previously so am not too fazed by that - but admittedly am a little puzzled by the access issues - ie digging a trench parallel to the house.

I've made enquiries with a chain of surveyors (Peter Cox) - initially I thought they looked like LPOC-linked fine olde purveyors of dampe and woodworme chemicals, but they advertise that most of their work is pre-WW1 and have worked on many important N Wales buildings including Portmerion; so I presume the must be kosher? Anyone have experience of them (PM me if you like) or recommendations of structural surveyors/engineers in the N Wales/Chester borderlands.

 

[chuckey]

The problem with diggers are that they are lousy for digging close to walls. I did what you intend to do but by hand, trench right up against the wall, about 9" wide and 60"deep, two layers of black viscrene up against the wall, 3" drainage pipe in bottom and the trench filled with 10mm pebbles. Now any water that soaks down through the soil hits the gravel and drops into the pipe and runs around the property (both sides) and exits(?) beyond the house.
The thing I now regret is that I did not put any insulation foam ("Claystop") between the plastic and the wall. It would have substantially reduced the heat loss through the wall.
Frank

 

[MdB]

The problem with diggers are that they are lousy for digging close to walls.

Agreed but it is possible. (well ok, not right up to the wall but close)

What you need is a digger which has a pivot at the bottom of the arm as well as the whole body being able to rotate. Using this facility I was able to run the trench right past the front of the greenhouse without actually hitting it (this surprised me a lot). I did manage to go straight through a water pipe but that is another story...

 

[Penners]

The problem with diggers are that they are lousy for digging close to walls.

If you can find a hire centre that has one, Volvo make a backhoe-loader that has a handy feature for digging close to walls. The knuckle between the main boom and the dipper (in human terms, the upper arm and the forearm) has a lateral swivel function as well as a vertical one. So by angling the main boom towards the wall and using the horizontal swivel on the central knuckle, you can get the dipper arm and the bucket parallel to the wall, right up against it.

Not that I would necessarily advocate this. Unless you're a bit of a whizz at operating a backhoe, it's better to start your trench at the farthest point from the wall, then carefully work your way towards the wall. This enables you to stop when you feel that you're getting dangerously close, and dig the last thin skin of soil away from the wall by hand.

 

[FamilyWiggs]

Splendid. Thanks Guys.

I'll look for a digger with a swivelly-pivoty-elbowy-thing.

It's obvious, but I hadn't thought of digging *towards* the wall. :roll:

 

[MdB]

It's obvious, but I hadn't thought of digging *towards* the wall. :roll:

Unless you are good, very good, you don't want to dig perpendicular to the wall. That is a recipe for taking a chunk out the house. I would dig a trench parallel to the wall and a short distance away. I would then dig the remainder by hand. I would be very worried about collapses though and cables, pipes etc.

 

[FamilyWiggs]

That's what I was think of doing MdB.

Without putting in those steel interlocking panels to prevent against collapse whilst working in the trench or building the retaining wall, how does one reasonably protect against collapse?

Does one dig a section, build the wall, then dig the next bit, etc - in order that there is never more than a metre or two of face that is unsupported?

 

[MdB]

Have a shallow angle for the bank? How shallow, I don't know. There are a large number of Elf'n'Safety regs on digging holes due to the number of people who have been squished. I don't know what they are though, sorry. 1.2m depth comes to mind but I'm not sure. It would seem sensible to get advice on this.

 

[Penners]

Is this any help?

http://www.hse.gov.uk/construction/safetytopics/excavations.htm

 

[Flyfisher]

Noooooooo - don't post H&S info for excavations in case FF junior gets ideas above his station. It's hard enough keeping social services away while I work him through the night to get some new drains finished, without having to worry about 'elf&safety as well. :wink:

 

[FamilyWiggs]

Very good of you to give him some proper light FF; must be costing a fortune at 500w. Could he not manage with an LED miner's lamp? 8)

 

[FamilyWiggs]

Is this any help?

http://www.hse.gov.uk/construction/safetytopics/excavations.htm

Thankyou Penners - very helpful and kind of you to search it out for me.

The more I think about this, the more significant an undertaking it is - and needs to be approached properly prepared. It's not a weekend hire from HSS and have a stab at it. Looks like I will need to consider carefully about support/battening during the works.

Has anybody done this themselves? The trench will be 1 storey deep and about 3 feet wide, and probably 30 feet in length across the 3 sides of the building. If not, can anyone point me in the direction of other t'internet fora they recommend?

Thanks.

 

[Flyfisher]

Very good of you to give him some proper light FF; must be costing a fortune at 500w. Could he not manage with an LED miner's lamp? 8)

300W actually, but it's a good point. I've got some candles somewhere . . . .