Lean to abutment cladding detail?

[junglejim]

Going to be starting this abutment to cladding in the next couple of weeks. I’ll be using vertical cladding so double battening (onto timber frame). Any tips or insights appreciated. 
many thanks

[Russell griffiths]

You will need a really robust design for waterproofing the window cill. 
any water getting around the cill will be further back into the building than the flashing from the roof, so any water can easily get behind the waterproof method for the roof. 
 

I have 5 windows all above a roof like this and it took some serious out the box thinking to get a good detail 

i ended up using a single part roof liquid membrane to waterproof the window cill area. 
 

or you need to take your lead flashing up high and dress it into the window area, with all corners welded, not just folded. 

[junglejim]

Thanks @Russell griffiths. That’s helpful.  I’ve lapped the roof membrane into the breather so anything going behind will run down. I’m interested to see what you did though… do you have any photos?

[Russell griffiths]

No photos. 
you need to stop water getting behind or under the roof flashing, the membrane is only there as a second defence. 
whatever flashing you are using needs to go really high and lap into the window area. 

[junglejim]

11 hours ago, Russell griffiths said:

No photos. 
you need to stop water getting behind or under the roof flashing, the membrane is only there as a second defence. 
whatever flashing you are using needs to go really high and lap into the window area. 

Thanks. I hadn’t really anticipated the extra challenge of water running in under the cill. I’ll be adding vertical cladding which will shed most of the water over the flashing but appreciate some may go behind  in which case I wonder if some kind of flash band to seal the lead to membrane / below window might be prudent.

 

or perhaps cutting the membrane and lapping lead underneath?

Edited February 5 by junglejim

[junglejim]

On 03/02/2025 at 22:18, Russell griffiths said:

You will need a really robust design for waterproofing the window cill. 
any water getting around the cill will be further back into the building than the flashing from the roof, so any water can easily get behind the waterproof method for the roof. 
 

I have 5 windows all above a roof like this and it took some serious out the box thinking to get a good detail 

i ended up using a single part roof liquid membrane to waterproof the window cill area. 
 

or you need to take your lead flashing up high and dress it into the window area, with all corners welded, not just folded. 

@Russell griffiths can I ask why you didn’t either tape the lead to the membrane or attach a piece of membrane to the current membrane and overlap the lead?

[Russell griffiths]

1 hour ago, junglejim said:

@Russell griffiths can I ask why you didn’t either tape the lead to the membrane or attach a piece of membrane to the current membrane and overlap the lead?

Mines not timberframe, no membrane on the walls.