Box off external rsj / universal beam

briaineo

Hi

Just wondering what’s the best option for finishing an external rsj?

Interior wise it’s noggins and then plasterboard I presume?

Exterior wise is it noggins and cement board? 254x102x26kg is the size of beams

Czhornet

Yes inside would be noggins and plaster board, outside I've seen noggins, with some marine ply attached, some DPC or similar over the ply and expanded metal mesh tacked on and plastered over.

BryanF

start with insulation continuity

briaineo

Probably should have mentioned the rsj is 4.2m over a 3.8m ope and there will be no plastering on wall, metal cladding to be used.

The 3.8m window will protrude approx 20mm outside of ope to be flush with the cladding when finished.

Not quite following the insulation continulality comment...

Metric Tensor

Assuminh a cavity wall. If it's 102 wide it's on the outer leaf only? With a corresponding one or something else over the inner leaf?

If we're talking outer leaf only then the insulation should continue in the cavity behind the outer beam so no cold bridging issue.

If there is metal sheeting down the face of the wall and it meets with the window frame then the next question is do you need to anchor the bottom of the metal sheeting to the steel lintel? If so you need some sort of standoff, plate, nogging, etc to provide fixing. If not then is any finish needed? It'll be hidden behind the metal sheeting. I'd galvanise it to be safe myself rather than relying completely on the weather tightness of the metal sheeting.

I've based the above on a lot of assumptions. Apologies if I'm not describing the situation accurately.

briaineo

Metric Tensor wrote: »

Assuminh a cavity wall. If it's 102 wide it's on the outer leaf only? With a corresponding one or something else over the inner leaf?

If we're talking outer leaf only then the insulation should continue in the cavity behind the outer beam so no cold bridging issue.

If there is metal sheeting down the face of the wall and it meets with the window frame then the next question is do you need to anchor the bottom of the metal sheeting to the steel lintel? If so you need some sort of standoff, plate, nogging, etc to provide fixing. If not then is any finish needed? It'll be hidden behind the metal sheeting. I'd galvanise it to be safe myself rather than relying completely on the weather tightness of the metal sheeting.

I've based the above on a lot of assumptions. Apologies if I'm not describing the situation accurately.

Hi thanks for reply

Yes it is a cavity wall and there is another rsj on the inside with insulation between them: engineer said you wouldn’t necessarily need to do anything just clad over it but it’s not galvanized and already in place, it red oxide painted that’s it.

The cladding is to be on a rail (2 rails) so the rail will need a few anchor points and extra flashing will (possibly lead) will be required over the window since it protrudes approx 20mm out from the wall so it is flush with the finished cladding.

The cladding will have joints 3 or 4 above the window for a tile type effect but would not be 100% confident that it’s fully water tight.

I want to box off the rsj as it would be done if no cladding was being used. Also wished to plaster over it to be sure?

Metric Tensor

I don't think there's any point plastering over it if the blocks that it supports are not plastered? There would be no continuity and hence no real protection.

There's a special rubberised water-resistant paint available for painting steel in marine uses so if you want water proof behaviour without galvanising maybe you could paint it with. Google "Sigmadur"

Perfect weather for painting!!

BryanF

briaineo wrote: »

Probably should have mentioned the rsj is 4.2m over a 3.8m ope and there will be no plastering on wall, metal cladding to be used.

The 3.8m window will protrude approx 20mm outside of ope to be flush with the cladding when finished.

Not quite following the insulation continulality comment...

Without a detail it’s hard to see the wall insulation overlap with the window head/jam

Gileadi

Fire resistance been considered?