Lead flashing directly under cill acceptable?

[warmington_ash]

Hi,

 

Our extension is progressing well and I'm looking for an answer I have to a query re the new roof.

 

We're proposing a pitched roof (as crudely drawn below, red). In order to achieve a suitable fall, I was planning to tie the lead flashing to the ridge tile directly under the stone cill. Is this likely to be acceptable?

 

With this, the pitch will be around 16 degrees, which is based on the pitch meeting the adjacent mono-pitch and gutter (which you can just see to the right of the photo).

 

Any help or advice would be appreciated.

[Russell griffiths]

Have you picked a roof covering ? As 16 degrees is low for a lot of coverings. 

[Conor]

No, we had the same issue and had to raise the sill of our bedroom window. Can't remember the exact gap needed but was around 150mm.

[LA3222]

2 hours ago, warmington_ash said:

Hi,

 

Our extension is progressing well and I'm looking for an answer I have to a query re the new roof.

 

We're proposing a pitched roof (as crudely drawn below, red). In order to achieve a suitable fall, I was planning to tie the lead flashing to the ridge tile directly under the stone cill. Is this likely to be acceptable?

 

With this, the pitch will be around 16 degrees, which is based on the pitch meeting the adjacent mono-pitch and gutter (which you can just see to the right of the photo).

 

Any help or advice would be appreciated.

What you have drawn is exactly like my sunroom roof. I used the sandtoft 20/20 tiles and the lead flashing goes up to the underside of the cill, about 50mm between the two I reckon. BC ain't complained🤷‍♂️

[Mr Punter]

I think you need to find out from Building Control.  They may also want you to have a cavity tray, which is very difficult to achieve.

[ETC]

You will definitely need cavity trays and flashing. I don’t think you’ll get away without a 150mm upstand between your roof and underside of your cill - but check with your local BCO - they might accept lead flashing directly to the cill since there should be a DPC directly under the cill under which you could chase the lead flashing into. Best job would be to put in cavity trays and lead flashing throughout complete with stop ends and bedweeps and a 150mm upstand.

[warmington_ash]

Thanks all for your comments.

 

I'm starting to think that a last minute switch to a flat roof is probably a good call? Obviously this would completely eradicate the issue with the ridge height, and retro fitting a cavity tray would be much simpler to do along a horizontal line (note that the stonework is in varying heights and widths, which will make retro fitting a cavity tray diagonally a very complex and expensive task).

 

A friend of mine who is a good with 3D stuff did actually draw this option for us when we first started planning this project. Obviously it's a change to the approved planning drawings, so I'd need to agree it with planners, but as it's to the rear of my property I'm not too worried about that.

 

Brickies are due for their final visit Friday, so this is all very late in the day! But better late than never I guess.... I'd certainly rather be having this discussion now instead of when my rafters are in place!

 

Any further thoughts would be really appreciated.

[CharlieKLP]

Flat roof actually looks gorgeous, and I love the stone/bricks you’re using. Nice job.