underpinning

[timegoesby]

In a barn conversion, is it worth underpinning the walls on the outside by digging a few trenches and pouring concrete in, backfilling and digging the remainder? Is it worth doing inside too to prevent movement? When excavating the centre to lay the new insulated floor I know it is possible for the walls to move. Anyone ever done this? I don't want the walls to move when the excavation starts. The main part of the barn will be a timber frame which takes the loadings. All suggestions welcome as barn conversions can be problematic.

[PJO]

There's rather a lot more to underpinning than that!

Maybe you should seek the opinion of a structural engineer in the first instance and then maybe a specialist.

It's not usually a DIY option and can run very expensive if you c*ck-up.

[Hugo Nebula]

On 6 Feb 2004 07:05:53 -0800, a particular chimpanzee named [e-mail] (timegoesby) randomly hit the keyboard and produced:

Depends on whether the walls need underpinning or not. If there is evidence of continuing movement, or the conversion is likely to cause movement (by undermining the foundations to lower a floor for instance), then yes. It isn't something one should attempt willy-nilly, and if it is required, you should carry it out as per a structural engineer's recommendations (which the Building Control will want you to do anyway).

My experience of timber framed barns is somewhat limited, but a substantial stone barn very rarely warrants underpinning, as the movement has usually occured soon after the structure was built, and the lime mortar allows for a lot of movement anyway. Most failures are caused by a lack of lateral restraint and inadequate buttressing.

It sounds like you need the advice of a structural engineer, and an architect or building surveyor.

[IMM]

As I see it: Didn't he say he just wanted no wall movement when the centre of the stone barn is excavated? That is not actually underpinning, which is digging under the existing foundations and pouring in concrete. This appears a logical move as even if a structural engineer says the foundations are correct there is no guarantee that there will not be sideways movement when excavating.

"Most failures are caused by a lack of lateral restraint and inadequate buttressing." "Lack of lateral restraint". He want to puts some in. Disturbing a stone wall probably resting on earth can cause big problems. Barn abandonment's are common because of foundation problems when the build starts.

Sounds good, but even that will not account for "lateral movement" when the build starts. He did say the walls are non-load-bearing, so the existing foundations should be adequate. I would rest the roof on the inner timber frame and leave the barn walls as virtually cladding holding only them selves up.

[Dave Plowman]

It's certainly a DIY option given that the majority of the cost is labour

- and not particularly skilled labour.

Of course it's advisable to get decent pro advice on any structural job.

[timegoesby]

Thanks to all who responded.

Some nearly got it. I should been mire specific. I will have a structural survey. The point is that I don't want the walls to move after any excavation. I know someone who had a survey and the foundations were assessed as good enough. The walls moved and it cost a lot of money to put right.

I was thinking of "side-pining" rather than underpinning. Anyone know how wide? I was thinking of 1 metre. Maybe this is too wide and it should be 18 inches wide (from the wall) and 1 metre deep.

[timegoesby]

Thanks to all who responded.

Some nearly got it. I should been mire specific. I will have a structural survey. The point is that I don't want the walls to move after any excavation. I know someone who had a survey and the foundations were assessed as good enough. The walls moved and it cost a lot of money to put right.

I was thinking of "side-pining" rather than underpinning. Anyone know how wide? I was thinking of 1 metre. Maybe this is too wide and it should be 18 inches wide (from the wall) and 1 metre deep.