Proper Tyvek housewrap & flex wrap installation

[Bagheera]

Hi all,

My timber framed garden room now has tyvek house wrap on the exterior and I need to cut out the window holes and flash them properly.

The way to do it in the US seems to be to cut the house wrap flush with the edges of the window holes and use flex wrap on the bottom cill wrapping 6 inches up the side. However, they seem to use windows with nailing flanges around the outside and then tape those flanges to the house wrap as well as doing a flap at the top.

Here in the UK we don't seem to have nailing flanges and the window are set into the window hole and screwed into the sides rather than the front. Should I then cut an 'I" with 45 degrees at the corners and wrap the house wrap around the edges of the window hole and then once the window has been installed, cut the excess house wrap flush with the inside of the window and then use a sealant?

I hope that's clear. Basically we don't do enough timber framed houses in the Uk for the information to be out there on best practice.

Thanks in advance to anyone who has done this and can help.

 

[bobsuerita]

we normally cut membrane at corners then wrap inside covering whole window reveal

 

[Bagheera]

I suspected as much. Do you use the tyvek flexwrap on the bottom? Anything else I should know?

 

[Bagheera]

Thanks. I cut them out today, wrapped round and stapled on the internal side. Photos on my project thread:

https://www.diynot.com/diy/threads/insulated-timber-framed-garden-room.474157/page-3#post-4000414