Lead flashing limitations

[Hobo84]

Hi,
Currentlly lagging behind of a self build project and decided to pay someone to put my roof structure up for me to tile etc...
The problem is that the roof has been built too close to 3 windows and the flashing will not be big enough. I should note that I've assumed and included 55mm for the roof tiles and batterns. 2 windows along the back of my house which run parrell to a wall plate have a 70mm gap and a 3rd window which sits above the slope of the pitch roof and a 20mm gap (at the pinch point). BC have said that I need at least a 75mm gap to pass.
The roof was always going to be tricky as the margins were quite tight to achieve a 18' pitch and keep a decent ceiling height. I've gone around and measured what the plans say and compared to what the chippy has actually built. It's 65mm higher that planned, which if built too I would pass with BC.
My solutions are to either remove the windows and rasie with a run of brickwork, then replace with new window or drop the roof by the 65mm.
I haven't paid the chppy yet as he still needs to complete the soffits/fascias. Is it the responcibility of the chippy to come back a correct the work (mean unpicking the entire roof) or is 65mm a reasonable amount to be out by and I change the windows myself?
Hope this makes sence. I really struggled explaining this!!
Thanks

 

[freddiemercurystwin]

So for clarity, you’re saying if the timbers - where they sit against the existing to wall if dropped 65mm lower would give you an adequate gap for your lead flashing and the pitch/tile combination would still be compliant? And that’s what the drawings show?

On the face of it if that’s the case it seems like a no brainer, why did the chippy build it 65mm higher? Is there a reason? Have you asked him? Will he have to scrap any timbers if he lowers it or just a bit of trimming here and there?

 

[chappers]

My guess is that you could drop that by 65mm with minimal alteration , re cut the birds mouths at the top and re cut the plumb cuts on the up and over bit. Probably wouldn't bother with the birds mouths at the wall plate. It is a pain but that's life.
As to whether 65mm matters depends on the job in hand and on this occasion it's an unreasonable amount, but when building the Eiffel tower 65mm too high or low probably didn't make much difference

 

[Toproofer]

Back windows might be ok as for the one on the slope you could remove the timber spar off the wall then put a smaller one in and form a box valley, secret gutter against the wall giving you more upstand for your lead flashing.other wise it's a big job altering all the roof!! And would you get the pitch if lowered?

 

[Hobo84]

It is a little more complicated to explain, but yes, it's 65mm too high..!! I'll try explain better. I have planned a vaulted ceiling round the back of my house leading to the garden and a normal ceiling arrangement in my garage/bathroom. It's the garage ceiling which was built the 65mm too high. If it was dropped then the side window would have the required clearance.
I have mentioned there is an issue to the chippy but BC was still looking into the issue at the time so we didn't speak in detail about the issue.
He was hired on the premise that I could help him (as it's a self-build and I was keen to be involved). Unfortunately he brought another lad with him and I was pretty much surplus. I did hang around at first and remember him saying something about the roof height, I hadn't built the gable so he had to prop the purlins/ridge board up until I managed to finish the block work. As he had a copy of the drawing I didn't pass any heat.
I think the issue is that he's placed ridge board right in the middle of the extension. It should of been slightly off centred but kept at the same pitch to pass the side window. This would of made the garage door height slightly lower that the back of the house. Hope that makes sense?! I imagine to fix it the rafters will need to come off, reposition the ridge board and relay them.

 

[Hobo84]

Thanks everyone.

I'll go back to my chippy and suggest the above and see what he says. I'm no pro so it's great to get use your experence/ideas!!!

 

[^woody^]

You dont need a 75mm gap as stated by building control. And you dont need to lower the roof.

You can flash under the cills and it will be OK.

Or you can leave the tiles and lath off under the cills to get lower height, and then use lead instead of tiles on a ply base.

 

[datarebal]

Personally I dont think the chippy is at fault here.
If you cut 65 mm out of the birds mouth then there isnt a whole lot left.
Its more of a design issue.
The pitch doesn't look 18 degrees to me ..could be wrong.
cavity trays? lack of will bite you one day.. solid walls? still need trays under windows. BC not say?
That aside, form a small flat area below each window this is easy to form in timber and lead.
problem solved.

 

[Hobo84]

Just to let you all know that BC have informed me to raise the window height or add a flat section. I've agreed with the chippy to replace the window, didn't think the flat section would look that good. He's agreed in princable it was his fault. He wrote on the wall his measurement of 2500mm to the top of the wall plate but built it to 2610mm.

I've caluated the pitch and it came to 17.6 degrees (which I think it pretty good).

Cavity trays... Sorry to sound like a numtpy but are you suggesting to add a cavity trays under all the window cills? The existing walls are soild but the new walls are cavity. As we're replaceing the windows I don't see why I wouldn't add them if it's recommended.

 

[datarebal]

Chippy sounds a good guy. The plate height generally isnt down to Carpenters.
So a plate height set by others, plus an 18 degree roof pitch rafter ends where they end..
The windows do look past best so obviously the easiest route would be replace to suit.
tray under windows is a wise move.
what tiles are you using to the extension?
have you checked the roof pitch?

 

[Hobo84]

He's been good so far. I did offer to put the wall plate on for him (it would of saved me having to dry pack underneath) but he wanted to do it.

Tile options were either the 20/20's of a remond mock mini (something like that). Think we're going with the remond. The supplier said the 20/20's can 'chatter' when windy.

Yeah I checked the pitch. it was 17.6 degrees.