Building off a set of RSJ's

[Jupiter01]

Hi Guys,

The footprint of upstairs is different to downstairs.
I have a set of RSJ's bolted together as per structural engineer specifications and wanted to check that you just build off these (using brick and block) in the normal way i.e cavity wall and wall ties, etc.

The beam will be covered by the plasterboard ceiling of downstairs.

I have a follow-on question but wanted to keep it simple to start with

Thanks in advance.

 

[John D v2.0]

Yes that's what our builders did, just make sure you fill with insulation at the bottom, then cavity tray to outside. The outer leaf is coming down to the beam so it's a risk for thermal bridging.

 

[Jupiter01]

Thanks @John D v2.0.
My builders started laying bricks onto the RSJ as I recall it. They did put the appropriate amounts of kingspan insulation in. I have plenty of insulation below the beam (above the ceiling from downstairs). There is a cavity tray where the windows are. Is that what you mean?

 

[John D v2.0]

There is a cavity tray where the windows are. Is that what you mean?

No the cavity tray should be above the RSJ and immediately above the flashing for the attached roof

 

[Jupiter01]

ummm...
I think I've been sold a dead horse

My walls have been built directly on the RSJ's and I am now worried that when moisture gets through the outer leaf and collects on my RSJ, it will seep through to the ceiling below. Out of interest I spoke with around 5 friends who've had similar extensions and confirmed that they've had exactly the same procedure in their properties and not experienced any issues. I may be over-thinking this but something doesn't feel right.

Can you please shed some light on this please.

 

[^woody^]

From internet somewhere. Don't forget the weep holes, and the tray should be built in to a bed joint in the inner leaf

 

[John D v2.0]

Can you please shed some light on this please.

You can get away with all sorts, but to guarantee no issues you have to do it properly. With missing cavity trays you may well never have any problems.

 

[Jupiter01]

I've been reading up on this and am reaching the conclusion that I need these retrofitted. I would appreciate your thoughts on this.
http://www.cavitytrays.com/pdf/23-Type-E.pdf

This would be the only proper solution as I see it.