Is he going to have a problem?

[bigbrian]

When I had my conservatory built last year, the builders had to go down

1.4 metres with the trench to hit something solid to build on. A Readymix lorry delivered the base and 6 guys barrowed it into the back garden.

My next door neighbour is having one built (different builder, and at much lower cost for a slightly smaller conservatory). There was one guy hand digging the trench - he started yesterday morning. Don't know how far down he went, but there wasn't anything like as much earth in the skip as when mine was dug - indeed, my builders had to get a second skip because they filled the first one up in a day,

This morning, when I went out (about 8.30), they were just starting to mix some concrete in a small mixer out on the front lawn to start pouring the concrete into the trench. By the time I cam back (about 2 pm) there's a three foot high brick wall already built

My concerns are

a) did they dig deep enough b) have they waited long enough before building the brick on the concrete

(He's away on business, and his wife is out all day at work, and I'm guessing neither of them has much of a clue of the right way to go about it, any more than I do really)

[Andy Cap]

I guess your builder complied with Building regs and he's hasn't.

When a neighbour of mine recently had an EXTENSION built, they made him go down about 1.5 metres, onto the chalk for a firm base.

This was about 1 metre below the 25cm thick footing the three-bedroom semi was sat on !

A conservatory can't require more than a three-bedroom semi can it.

Andy

[Nigel Molesworth]

No such thing for a conservatory.

My builder was delighted when I told him the base I had prepared actually had footings, many just use a raft. Unless you are on incredibly soft sub-soil, I would have thought that 0.5m was ample.

Did your builder charge you for "extras"?

[Rednadnerb]

I only went down 300mm with the footings for my conservatory, the slab goes up and down with the seasons opening a 1/4" gap in one corner which closes again in summer but I don't care because it's only a conservatory!

[Andy Cap]

Well he might be planning on an extension in the future ! ;-)

Andy

[Dave Plowman (News)]

That's a recipe for the two separating. Happened to a friend when adding to a Victorian building. After a few years it was cheaper to simply demolish the lot.

[Weatherlawyer]

That sounds more like water movement. You must have a layer of impermiable soil building up a resvoir under it when it is wet (it could open in a wet summer and close in a dry winter.) Look up "hydraulics + soil".

I must admit. though, that it sounds the wrong way around. But what do I know.

Whatever, the footings and the concrete pad just serve to hold the unit together, not to bond it to another unit. Obviously going down to the bedrock would join them together provided the original was on it too.

I believe the minimum for a concrete foot is aout 18" to keep it out of the frost. The bricks can crack but are not likely to, as they are a small enough section to cope with frost. The footing must not crack, or the wall will fall.

The frame of the conservatory will be screwed to the walls of the house, I imagine. that should hold it until the screws snap or pull out, or the wall gives or something.

[Andy Cap]

I'll tell him ! :-)

Andy

[meow2222]

Last one of those bolt on adjustable wall bonding jobs I saw has already cracked the house bricks into pieces due to the wall moving. Seemed fairly obvious it would, but there ya go. Seems to me these are a bad design, and much better would be to put threaded studs into the wall and plastic sleeve them. This then prevents sideways movement, as wanted, but allows the new wall and house to move apart to some degree, which is much better than having the wall break up.

Its also cheaper of course. =A32 for enough ss threaded stud, not much for a little (optional) resin. Not sure about the cost of 1/4" pipe, but very little. And it takes no longer to do. Junk product really.

NT

[none]

Depth and type of founds is entirely dependent on ground conditions and loadings, would reccomend any building attached to an existing building that has been in place a number of yeras has the found seperated with board from the original and that walls are connected with 'crocodile' type wall ties that allow vertical movement which is inevitable due to differential settlement.

[dg]

A conservatory puts relatively little load on the ground, and copes with movement well. However I would not expect much movement from a conservatory

1.4 m deep for a conservatory is excessive compared to 1m for 2 storey extensions which is commonplace.

I would question which builder actually knew his stuff?

Where you by chance charged extra for the foundations?

dg

[nightjar]

That is excessive, unless there is a very good reason, such as a Willow tree nearby on clay soil.

...

That depends on why yours was so deep and, if it was for something like a thirsty tree, how far away that is from your neighbour's property.

Colin Bignell

[Lobster]

So what's the answer - there's no building regs that account for this, are there? Should old properties just never be extended?

David (now slightly worried about the cracks in the plaster of his recently-extended Edwardian property...)

[Tony Bryer]

Probably not, but conservatories (that pass certain tests) are exempt from Building Regs.

[Rob Morley]

If you're really worried you could underpin the whole house ...

[bigbrian]

No, I wasn't. Indeed, the builders who were working on my build were also operating on another site nearby at the same time where, so they said, they were down to 2 metres and still going. They were talking about piling it, and the conservatory company, who had already had the unit custom built, were trying to get extra money from the customer, who was telling them to get lost, cos he knew they couldn't do anything else with the conservatory

[bigbrian]

No trees to speak of. The guy doing the digging said they normally have to go about 1 metre, but he always keeps going until he hits something strong enough to build on. It was all soil until he hit the chalk at 1.4 meters.

[Tim S]

You're supposed to go below any organic matter. It's not per-se necessary to hit rock. Doesn't do any harm of course - just not necessary most of the time.

Tim

[nightjar]

He would have had fun at a site I was involved in developing, many years ago. The trial pit showed chalk at 6 feet down, so the chief engineer commissioned trial borings to only 20 feet. It turned out that there was an underground chalk cliff across the site and in parts he had to rebore, to find that the bedrock was over 60 feet down across about half the area.

Colin Bignell

[Tony Bryer]

I had one of those in my BCO days on Kingston Hill: phone rings "we've gone down ten foot and still haven't hit clay". Well up there you wouldn't - going down 2'6" on to the sand and ballast is fine.