Timber cladding detail around windows

[pezzer]

Hi,

I'm building a timber frame, timber clad extension. I'm fitting painted timber windows, and am rather confused about the detailing around the window.

Everything I can find mentions preformed flashings at the head. Does anyone know where I can get these, and what they're called?

Also, from what I can tell the external breather membrane and internal vapour barrier are supposed to be overlapped. Where should this happen (ie. externally / internally?)

Should there be a DPC anywhere?

Thanks!

 

[freddiemercurystwin]

There are various ways of detailing it eg

http://www.woodspec.ie/media/woodspec/content/sectionbdetaileddrawings/detail_b_12.2.2.jpg

http://www.scotland.gov.uk/Publications/2002/03/15098/8744

http://www.p3estates.co.uk/static/uploads/pdf/Timber_Cladding.pdf

Pre-formed flshings will be expensive unless you can get one 'off the shelf' that happens to suit your set-up. This really needs to be thought about alongside the battens/windows/type of cladding etc. They're called Preformed flashings! They usually come in aluminium and are powder coated.

For an extension lead would be the easiest and cheaper.

http://www.calderlead.co.uk/wp-content/uploads/2011/07/Calder-Guide-to-Good-Leadwork.pdf

the vapour barrier will just wrap around the underside of the headers or under the cill to meet the breather membrane.

If flashings are used no need for a dpc that's what your flashing is doing. At the head you dress the brethable membrane down over the top of the flashing. At the cill the flashing should be going back to the underside of the window cill.

Many ways to do it really, no one best solution.

 

[^woody^]

Also, from what I can tell the external breather membrane and internal vapour barrier are supposed to be overlapped. Where should this happen (ie. externally / internally?)

No, that's not correct - the timber frame prevents this!

You need form a drip detail above the window so that any water running down the membrane behind the cladding is cast off the drip.

Whether you form this with lead or a suitable substitute or DPC material is up to you. Your membrane will lap over this

It also need to extend past the jambs, and not just be the width of the window opening