Flashing under cills

[voodey65]

Hi, I'm building my own extension and have made a bit of a cock up with the roof finishing height. It comes just under the cills for the 1st floor windows whuch causes me problems with the flashing. In my head I've got a few options, 1. Replace the cills with a thinner ones to allow more room or 2. Cut the existing cills to achieve the same outcome. There are 2 cills, each different sizes and there's about 50mm bewteen them and the roof. I know I should have got my heights right but it's my first try . Any ideas would be much aprreciated

 

[DiyNutJob]

Picture speaks a thousand words.

 

[voodey65]

It does but its too dark for pictures right now. Hopefully this scribbled drawing helps a bit. Of not ill get a proper pic tomorrow

 

[noseall]

Hi, I'm building my own extension and have made a bit of a cock up with the roof finishing height. It comes just under the cills for the 1st floor windows whuch causes me problems with the flashing. In my head I've got a few options, 1. Replace the cills with a thinner ones to allow more room or 2. Cut the existing cills to achieve the same outcome. There are 2 cills, each different sizes and there's about 50mm bewteen them and the roof. I know I should have got my heights right but it's my first try . Any ideas would be much aprreciated

Is there 50mm of clearance, once the roof materials (tiles etc) are in place? Have you fitted the tiles yet?

We'd pre-empt this whilst at the roof carcass stage and dress some lead under the sill, prior to tiling. It will be largely protected under there in any case. Either side of the window jambs needs a wee bit of care, as the lead will sit higher at this point, so will need some careful dressing into each window reveal.

 

[voodey65]

Is there 50mm of clearance, once the roof materials (tiles etc) are in place? Have you fitted the tiles yet?

We'd pre-empt this whilst at the roof carcass stage and dress some lead under the sill, prior to tiling. It will be largely protected under there in any case. Either side of the window jambs needs a wee bit of care, as the lead will sit higher at this point, so will need some careful dressing into each window reveal.

There will be 50mm clearance once the tiles have gone on and I havent got that far just yet so that's good. When you say dress the lead under the cill, is this as normal only without the 150mm upstand and then 150mm upstand where there is no cill? Like my picture? Thank you for your reply

 

[freddiemercurystwin]

Yes that's the ticket, all assuming you don't have an overzealous BCO ....

Just make sure the lead is dressed properly so that it ties in with the ones under the cill as nosey mentioned.

 

[noseall]

There will be 50mm clearance once the tiles have gone on and I havent got that far just yet so that's good. When you say dress the lead under the cill, is this as normal only without the 150mm upstand and then 150mm upstand where there is no cill? Like my picture? Thank you for your reply

A 150mm upstand is only relevant where its needed. Windows, glass and sills, don't wick water.

 

[voodey65]

Cheers for this, easier than I expected and my BCO has been decent up to this point so we shall see

 

[noseall]

Cheers for this, easier than I expected and my BCO has been decent up to this point so we shall see

BCO?
If 150mm splash was ever an issue with windows, then there would need to be lead sat atop every sill.
As I said, you need to be a wee bit creative with the lead at the jambs/reveals, and how you dress the lead into them.

 

[voodey65]

The lead shouldn't come passed the sills anyway they're 200mm thick so it's just getting it nicely fit around them