cheek panels

[dpmiller]

Well not really, but this is the closest section I can think of to put the Q...

 

Above our porch- and in a similar fashion at the rear of the house- we've small triangular areas that need building up as spandrel panels to continue a return block wall. Crappy photo of the scenario below, the blockwork will rise as a vertical edge to the left.

 

So I've 150mm of depth to fill (100mm block + 50mm cavity).  The outside will be half inch renderboard but what else? 140mm treated CLS straight onto the TF, or is some counterbatten a Good Idea? Studs are all 400ctrs max...

[dpmiller]

any thoughts here please?

[ProDave]

There is a material I have seen used for this but I don't know it's name. It is a sort of cement board but with a woven structure that looks a bit like straw.  I think it was in 50mm thick panels where I saw it used

 

I think this may be them https://www.savolit.co.uk/savolit

 

[Mr Punter]

From outside render, renderboard, 38 x 50 counterbatten fixed with long screws through, membrane, Celotex - thickness to suit, existing timber frame.

[dpmiller]

@Mr Punter I'm intrigued- why the Celotex? Seems like an expensive way just to make up depth and as all the specc'ed insulation is on the inside of the frame would this not require reconsideration of condensation risk?

 

I presume that any airgaps in this built panel don't have to align with the TF-block cavity?

 

On the render side of things, as we're undecided as to whether it'll be a simple sand and cement affair or a monocouche would it be safest to site the renderboard back behind the block a bit with EML on?

[Mr Punter]

I suggested Celotex as dormer cheeks are often a lighter weight construction than the main walls - maybe 89mm - so sometimes the extra insulation can help prevent a cold spot.  If you are planning on the render being continuous from blockwork to render board then you could look at stainless eml over the render board with a big lap onto the blocks or an expansion gap bead between the 2 materials. Another option may be to tile hang or lead clad this bit but it may look a bit crap.

[dpmiller]

Rendered over with EML sounds like a plan...

 

The portions I'm looking at are part of the main TF so 140mm with all the insulation package inside, so it really is just choosing a means of standing the render clear of the frame a distance to match the blockwork. They aren't even massive areas, perhaps 1.5m2 each panel.

 

I do have one "normal" dormer to deal with at the back but that'll be easier to detail as there's nothing it needs to align with.

[dpmiller]

...and time to do  the dormer. The side panels worked out nicely, we went with an aluminium abutment tray from Kytun and will do the same at the sides of the dormer.

 

But a simple Q.  Do (why?) all dormers require a window tray? The -upvc- window in our dormer is fitted exactly the same as the rest of the house- firestop batten around the top and sides of the opening, window fitted flush with. There'll be a upvc cill screwed to the bottom of the frame externally, and the whole clad in renderboard. Why would this window need a tray where the rest of the windows in the house don't? All have a ventilated free-draining cavity after all...

[LA3222]

@dpmiller, do you have some photos you could stick up of how you solved all the details of your dormer?  I am trying to get my head around how the flashing should be done and like you, my dormers will be rendered.  I believe there should be lead soakers u dear the tiles at the side which are nailed to the dormer cheek under the counterbattens?  Then once the tiles are down they should have lead flashing over them which goes up the dormer cheek over the counterbattens?  The render board goes on top of the battens and then render away?

 

I'm not at all sure if I'm thinking along the right lines here, if you could give me a steer it would be appreciated

 

Ta

 

Jamie. 

[dpmiller]

I'll see if I can find any but yes that's pretty much where I am. I may run a narrow strip of leadax down the edge of the renderboard before the render goes on tho.