Any building regs experts in the forum?

cyclonebri1

I'll keep this short as I'm sure more info will be needed. We are having a "wraparound" extension built on one corner of the house.

We need to remove as much as possible of the back face of the corner to allow the new bit to blend with the old. What is the min safe bearing needed for the new lintels, this being standard cavity brick/block construction.

I know a drawing would help but no can do,

Doozergirl

A structural engineer would have to work out the minimum bearings needed for your RSJ, it depends on what is to be supported and therefore the size of your RSJ. Building control will expect you to adhere to the calculations.

Our wraparound we have removed the original back of the house top and bottom and have had to leave at least 450mm bearings of the original back wall to hold up the roof or we'd have had to start piling and underpinning.

I'm not entirely sure what you mean by 'back face of the corner'? so perhaps we're talking at cross purposes.

If you phone the building control officer, they will happily clarify for you. They don't always tell you the right thing though and go overboard, but that's a whole other story!

cyclonebri1

Doozergirl wrote: »

A structural engineer would have to work out the minimum bearings needed for your RSJ, it depends on what is to be supported and therefore the size of your RSJ. Building control will expect you to adhere to the calculations.

Our wraparound we have removed the original back of the house top and bottom and have had to leave at least 450mm bearings of the original back wall to hold up the roof or we'd have had to start piling and underpinning.

I'm not entirely sure what you mean by 'back face of the corner'? so perhaps we're talking at cross purposes.

If you phone the building control officer, they will happily clarify for you. They don't always tell you the right thing though and go overboard, but that's a whole other story!

Hi,

I don't think so, from the outside corner to the end of the lintel support
Yes we are approaching this form allsides. ie, the builder, the druaghts guy, and the building regs bloke

The calcs have been done but I think the info has not been made clear to the builder?

You say 450 as a bearing surface?, which I take to be from the original outide skin to the end of the support?

That equates to 150 to 175 extension to the interior wall, dependant on cavity. Our builder is saying it has to be a min of 750. To be honest I don't believe him

Added info;

I think the builder has mis interpreted the plan. He thought he could remove the existing widdow and door on the rear corner, which share a common lintel.

That's not what the plans show hence his struggle, as it will need additional rsj's etc which I suspect he hasn't priced for.

Doozergirl

No, I gsaid it wrong didn't I. It's 450mm inside the house. So I got the boy to measure and the wall outside is 230mm. Makes it 680mm but that was based on the structural engineer calculating it.

That doesn't exactly help you does it because mine is now about the same size as what your builder says!

iamcornholio

Not sure what's going on there, but the minimum bearing for a lintel is 100mm.

If you are referring to the minimum width of a pier supporting a lintel, then it depends on the loading, and it is possible to have something like 215 x 215 (or x 250 if a cavity wall)

If piers are too slender, then a steel column can be used

cyclonebri1

iamcornholio wrote: »

Not sure what's going on there, but the minimum bearing for a lintel is 100mm.

If you are referring to the minimum width of a pier supporting a lintel, then it depends on the loading, and it is possible to have something like 215 x 215 (or x 250 if a cavity wall)

If piers are too slender, then a steel column can be used

I new it would get confusing. It's not the width, it's the length of bearing surface. The plans guy has speced two beams one for each in and outside skin and then bolted together. They will of course be 100 mm min width

We want to remove as much wal as possible up to the external corner. It's how much of the corner return do nwe have to leave in.

I posted this on a couple of other forums so may be back with some more detailed info later.

ormus

its impossible to give an accurate figure. we would need a full drawing and spec, of the buidling.
ie a bungalow would be very different to a 3 or 4 storey house.

cyclonebri1

ormus wrote: »

its impossible to give an accurate figure. we would need a full drawing and spec, of the buidling.
ie a bungalow would be very different to a 3 or 4 storey house.

No problem the is sorted apart from reminding the builder to read the spec before he quotes, :wall::wall::wall:, that is yet to be resolved

Doozergirl

If he's using two lintels then is he just using concrete ones?

The bearing for those is quite small, certainly not 650mm, but there is a maximum length before you have to use an RSJ.

cyclonebri1

Doozergirl wrote: »

If he's using two lintels then is he just using concrete ones?

The bearing for those is quite small, certainly not 650mm, but there is a maximum length before you have to use an RSJ.

No rsj's bolted together.

I think we have resolved this, the designer, as in struc eng , didn't show it clearly on the plans, did the calcs, but the actuall buider missinterpreted, I can see why.

Wer will now take this forward, cheers, to all. :T