Large gap above window

[rreanor]

Hello,

I had to knock off some blown plaster around a window, although i've discovered a large gap above the window frame. This gap was originally covered by a thin (a few mm) piece of wood nailed into the wooden lintel above it, and then plastered over. God knows how the plaster stayed up so long!

Any suggestions on what to fill this gap with? I dont want to put another beam in, as there's nothing to rest it on. I was thinking expanding foam, but i still need to plaster over it after.

I think perhaps expanding foam, followed by a more secure covering, followed by mesh then plaster.

See pic.

 

[Harry Bloomfield]

Expanding foam, trimmed down once set, to just below the surface to allow for plaster.

 

[rreanor]

Expanding foam, trimmed down once set, to just below the surface to allow for plaster.

Can you plaster over expanding foam? Surely the suction is ridiculously high.

 

[Harry Bloomfield]

Can you plaster over expanding foam? Surely the suction is ridiculously high.

Wet it well.

 

[RandomGrinch]

Hi,

It may be an extra step, but I would consider using expanding foam to fill most of the gap and then also use it to attach a small panel of plasterboard level with the exposed bricks. The missing section can then be patch plastered.

The plasterboard would need to be braced to stop excess expansion of the foam pushing it out too far.

If you go for a low expansion type like:

https://www.toolstation.com/soudal-genius-gun-plasterboard-adhesive-foam/p99304

you could build up the layers of foam in a more controlled way.