Expansion joints and firestops..

ali68 · 16 Apr 2009

Starting to block in the extension now (it's timberframe). One wall is 14Mtr long therefore requiring two expansion joints in the blockwork.

Can I place these expansion joints adjacent to my firestops (2x2 with dpc stapled to the surface).

i.e. down the centre line of the firestop.

Spoke to an ex-builder who says "No you cant" and went on to say they are not needed! so I not sure how cosha his advise is, anyhow BCO will insist they are there.

Once again thank you!!

^woody^ · 16 Apr 2009

Why do you need two joints in 14m - one should do

Firestops do a specific job at certain places in the frame, if this coincides with the location of an expansion joint, then there is no reason why the two can't be adjacent

Shytalkz · 16 Apr 2009

Blockwork is every 6m including around corners.

And if you do that, it will only go and crack some place else.

^woody^ · 16 Apr 2009

But its not bang on every 6m - ie an extra 1m is not going to make any difference, but two joints in this wall is going to weaken it unecessarily

Shytalkz · 16 Apr 2009

No and, equally, putting them in at every four metres is not necessarily going to stop it cracking.

Why will it be weaker? It's a timber framed structure, so the timber frame is doing the work, the blockwork is just a veneer. It will be tied back to the frame; you just put double-intensity ties either side of the joint to stop it flapping.

denso13 · 16 Apr 2009

Spacing should be halved from an internal or external corner, if you have any, so 3m max in that case.

Shytalkz · 16 Apr 2009

Not so.

denso13 · 16 Apr 2009

How not?

ali68 · 16 Apr 2009

^woody^ said:
Why do you need two joints in 14m - one should do

Just going by the spec on the drawing, they state a joint every 6mtr.

Seem to have opened a can of worms ..

noseall · 16 Apr 2009

ali68 said:
Seem to have opened a can of worms ..

Great.

^woody^ · 16 Apr 2009

Worms are good

tawelfryn · 16 Apr 2009

Always amused me expansion joints, They want the wall to expand and contract, yet they specify, wall ties tying the two leaves, (or nailed to timber frame) at every course of blocks, or 3 courses of bricks, either side of the joint, cant see it doing much expansion or contraction myself after all that

hotrod · 16 Apr 2009

Aaaarrghhhhhhh.... not this old badger again

tawelfryn said:
Always amused me expansion joints

Ain't that the truth, whatever did we do before expansion joints were dreamt up.........

denso13 · 16 Apr 2009

http://www.nhbc.co.uk/NHBCPublications/LiteratureLibrary/Technical/filedownload,21417,en.pdf page 30, is one example

Whether it helps or not, that's a different matter.

^woody^ · 16 Apr 2009

tawelfryn said:
...They want the wall to expand and contract, yet they specify, wall ties tying the two leaves, etcl:

The wall will expand/contract along its length, and there is enough flexibility in the ties to accomodate this. The ties are intended to tie the walls together and prevent movement in the other direction.

We have some properties near us where the wall above DPC is built in some soft red brick and this has expanded over the past 40 years and overhangs the wall below DPC by 20mm at each end of the gable - so in 7m it has expanded 40mm

On some older terraces, where every second house is set back by about 1m, the walls have expanded by about 20mm or so, and cracked every return on the set back

The silly thing though, is that some bricks/blocks will cause the wall to expand more than others, so the general guidance of joints every x metres is not always necessary

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Expansion joints and firestops..

hotrod

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