Lean to extension over outside wall... weep holes inside?!

[mayfel]

Hi!

I'm planning a lean to extension on the back of the house. However, the lintels over the exterior doors and windows have cavity trays and weep holes; as does the bottom of the wall. Surely when water trickles down the inside of the cavity it's going to weep into my new inside space! How is this usually solved?

Cheers,
M

 

[freddiemercurystwin]

If you're doing a pukka job you'll retrofit a cavity tray where your new roof meets the existing wall thus eradicating the issue. Of course there will be the usual tirade of regulars on here who will bleat on that it's a pain but if you want to ensure a dry extension then that's the way to go. Some Building Control Inspectors insist on their fitment anyway though if you use a Private Inspector they will turn a blind eye cos they know which side their breads buttered.

 

[mayfel]

Cheers man, good to know!

 

[noseall]

Not having a CT does not automatically mean your house will be wet either.

Check those existing weep vents out and see if ANY water has passed through them.

Just for you Freddie, note the CT over the arch window....

Untitled

• noseall
• 14 May 2015
• 2

 

[GoferBlue1947]

If you're doing a pukka job you'll retrofit a cavity tray where your new roof meets the existing wall thus eradicating the issue. Of course there will be the usual tirade of regulars on here who will bleat on that it's a pain but if you want to ensure a dry extension then that's the way to go. Some Building Control Inspectors insist on their fitment anyway though if you use a Private Inspector they will turn a blind eye cos they know which side their breads buttered.

What if the cavity has been retro-filled with EPS beads/adhesive coated?
What if the house wall above extension is PVC cladded so no water can get at the wall?

 

[freddiemercurystwin]

If you're doing a pukka job you'll retrofit a cavity tray where your new roof meets the existing wall thus eradicating the issue. Of course there will be the usual tirade of regulars on here who will bleat on that it's a pain but if you want to ensure a dry extension then that's the way to go. Some Building Control Inspectors insist on their fitment anyway though if you use a Private Inspector they will turn a blind eye cos they know which side their breads buttered.

What if the cavity has been retro-filled with EPS beads/adhesive coated?
What if the house wall above extension is PVC cladded so no water can get at the wall?

There can be circumstances where retrofitting may not be possible or is inappropriate, however one has to consider the cost of retrofitting one a year or so after the builder has left site, living with some damp, establishing why, allowing the wall to dry out, maybe re-plastering the wall, scaffolding over the extension and retrofitting later. Far more economical to do it in the first place.

 

[GoferBlue1947]

If you're doing a pukka job you'll retrofit a cavity tray where your new roof meets the existing wall thus eradicating the issue. Of course there will be the usual tirade of regulars on here who will bleat on that it's a pain but if you want to ensure a dry extension then that's the way to go. Some Building Control Inspectors insist on their fitment anyway though if you use a Private Inspector they will turn a blind eye cos they know which side their breads buttered.

What if the cavity has been retro-filled with EPS beads/adhesive coated?
What if the house wall above extension is PVC cladded so no water can get at the wall?

There can be circumstances where retrofitting may not be possible or is inappropriate, however one has to consider the cost of retrofitting one a year or so after the builder has left site, living with some damp, establishing why, allowing the wall to dry out, maybe re-plastering the wall, scaffolding over the extension and retrofitting later. Far more economical to do it in the first place.

I only ask because my son had EPS bead insulation put in the cavity walls of his house and he has similar weep holes above the lintels. He apparently has never seen water coming out of them prior to the insulation. Re cladding. I wondered if the OP could use this above the extension and thereby avoid any discussion of new cavity trays?