Crappy roof junction detail...

[Mulberry View]

I'm fighting for my life trying to get our house water-tight, after the relationship with our Architect broke down, hemorrhaging money trying to get other Architects to fill in the blanks. I built the shell as per the plans and sadly didn't think hard enough about the next steps. This is what I have at my roofline...

 

 

That's a 200mm timber hard-edge upstand, it contains the Celotex for the warm room. This is how the Architect detailed it...

 

 

Clearly we cannot render directly onto Timber. I spotted it after the shell was built and so added an extra 50mm around the perimeter of the roof in a late-stage adhoc amendment, to enable an overhang big enough to take a secondary layer of EPS that I would add to the whole building to cover everything up and give a single layer to render onto.

 

However, I'm now second-guessing it, does the timber need ventilating? Would I be better to utilise a rain-screen system here? I'm thinking of vertical tile-battens with render board attached and render onto that with an airflow passage behind it.

 

Any help is VERY much appreciated.

[Russell griffiths]

Go and get a length of anthracite coloured upvc facia, use this as a mock up. 
cut a couple of pieces to cover that wood up 

try fitting flush to the wood and see how it looks with the render

try adding a 25mm batten to that timber then the upvc, see what you think. 
 

if any of these ideas are good i would then chuck the upvc away and get the profile you want bent up and powder coated 

render comes upwards and finishes with a stop bead against the aluminium, get a coloured stop bead, or spray them, unless your having white render of course. 

[Oz07]

Presumably this timber showing around the edge is no less ventilated than any of the other pieces? That section shows another piece inside of this.  Good question though I bet most people would just cover it up without a thought. 

[Mulberry View]

3 hours ago, Russell griffiths said:

Go and get a length of anthracite coloured upvc facia, use this as a mock up. 
cut a couple of pieces to cover that wood up 

try fitting flush to the wood and see how it looks with the render

try adding a 25mm batten to that timber then the upvc, see what you think. 
 

if any of these ideas are good i would then chuck the upvc away and get the profile you want bent up and powder coated 

render comes upwards and finishes with a stop bead against the aluminium, get a coloured stop bead, or spray them, unless your having white render of course. 

 

All very well, but there's about 60 metres to do. It'd have a lot of joins too.

[Firsttimer]

Is there a way you can get a vapour barrier covering the upstands and not have it pierced by fixings ?

 

The batons and cement board sounds like a good idea. 

 

Cladding might be another thing to think about with render beneath it. This might look aesthetically more pleasing. Rather than having 27mm plus lip between the vented and unvented space.

[JohnMo]

On 27/05/2025 at 16:02, Mulberry View said:

 

All very well, but there's about 60 metres to do. It'd have a lot of joins too.

So how many joints that are not on corners? What's wrong with a joint or two, they are not seen, unless you start looking for them. Your gutters will be covering it anyway, so visually invisible. Too much other stuff going on for the eye to pick up on that detail. Step back a little and don't over think it.

 

Or do a wooden facing board and have it wrapped in zinc while they are doing the roof? Then render up to the zinc