Structural wooden Beam

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The local builder doing some work for me has opened up the rear wall of a single floored house and used 4 floor joists bolted together to hold up the wall above it which has a right angled triangle of double brick work above it forming the roof slope. One end of the beam sits on the side wall at roof gutter level, the other end sits under the apex on the party wall, the brickwork above at the party wall end is about 1.6m high. Span is about 2.5m . Does the supporting joist sound ok, he tells me a structural engineer did the calculations and its to be encased in plaster board.

[Dave Plowman (News)]

Did you get the bill from the structural engineer? That's what happened here when a builder had to use one.

I'd say it pretty unusual to support brickwork on wood these days.

[RobertL]

Have building control approved it?

Robert

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I suspect not

[John Rumm]

The short answer is that based on what little detail we have, its probably ok.

The lintel will be carrying all the bricks in the "load triangle" directly above it (i.e. visualise a triangle with sides leaning inward from each end of the lintel at 45 degrees meeting at an apex above the centre of the lintel). That sounds like an area of around 1.5m^2. Since you have a fairly shallow roof angle by the sounds of it, you may find some of that is full of nothing but air. However if we assume its all masonry, and take the weight of a wall at about 4.5nN/m^2 that's an all up weight of say 7.5kN (allowing a bit of leeway). You can look at that as a uniformly distributed load of about 3kN/m of lintel. Assuming by "floor joists" you mean four 200 x 50 timbers bolted together, then that should be well inside their capacity (in fact you would be hard pushed to even measure any deflection in the centre of the span with that load).

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Thanks

[Phil L]

It'll be fine, until it rots, which usually starts at one, or even both ends. It needs to be steel, and for the price of it, I can't fathom out why he has chosen wood - I've just used a 4m long, 100mm X 200mm steel beam to hold up an upstairs wall in a 2 storey house and it cost about £60. Obviously you would need two 2.5m lengths, one for each skin of brickwork, but I can't see it being much more, the timber he's bought, along with the bolts and the time used bolting everything together must have cost more than this and it has a very limited life compared to steel.

If it's structural work he's doing, and it sounds like it is, the BCO should be involved, and I'm 99% certain he would not allow this.

[John Rumm]

To clarify a point, My answer was in relation to the structural aspect of the work. I also agree with the others that its slightly unusual to use wood for this application in this day and age unless its for restoration/preservation work. Ready made steel lintels are surprisingly cheap.

[Dave Plowman (News)]

The one in my Victorian house is in rot free condition, but has sagged in the middle.

[Jules Richardson]

We've got structural supports like that in our place, and they've been that way for 60-odd years. Admittedly it's all timber construction this side of the pond rather than brick - but with 2 storeys I imagine the weight they're supporting is quite significant.

I suppose you could ask if there's a good reason for not using steel in your situation, though.

cheers

Jules

[Tony Bryer]

No argument from me. A risk when supporting brickwork off timber is that the timber has a higher moisture content when fixed than it will ultimately have and so will shrink a little. And as with steel beams, the beam needs to be properly preloaded against the wall above by wedging or slate packing, not just mortaring in any gap.

[John Rumm]

A retired builder friend of mine (also a great fan of slate for packing in these applications), also rated "dry packing" as an alternative for some tricky cases. Basically a practically dry strong mortar mix (probably no more moisture than just that in the damp sand), physically rammed in hard and tight, and then allowed to cure naturally. Supposed to result in practically no shrinkage.

[Hugo Nebula]

As the house owner you are ultimately liable for any work on your property, so I would suggest you should make it your business to be aware.