Spare room rip out - how to deal with this window sill?

[Participant]

Hi all

Just starting on the next project in my room-by-room renovation.

I've started gutting the room and the window sill was very out of level and wobbly, so I removed it (and have retained it) and found...

There was a lot of loose plaster, which I have removed (or will remove).

Any recommendations as to the best way to sort out the sill please, i.e. install it correctly and make it level? Is best practice using wooden packers and screwing into them, gripfill, expanding foam, bonding plaster, other?

The whole room will be replastered with bonding where required for larger holes.

Thanks.

 

[Participant]

Thanks all. Had never heard of cavity closers but they sound like a good idea.

Lots of options, is the sill going to be white and painted? If so I’d just screw it down and fill/sand and paint over the countersink screw heads.

Sill is currently a nasty old brown varnish, which will be sanded, sealed with zinsser bin, then primed and painted white.

I think then the plan is to remove the old wooden whatevers, build up with ply or plasterboard, fit a cavity closer, then attach the shelf to the blocks with grab adhesive, levelling with plastic packers as needed.

 

[Participant]

Foam the wood back on and move on. The one I removed was held on this way and it took a lot of effort to shift.

Just any old expanding foam?

 

[Participant]

Cheers all, really helpful.

Any reason I need a cavity closer if I do a good job of sealing the sill / board with caulk / silicone once it's level?

I think I'm just going to remove the wooden packers you can see, glue some plasterboard to the block with some foam adhesive, then glue the sill to the plasterboard with the same foam adhesive and some glazing packers to level.

Shouldn't be too hard and I think strikes the right balance between ease and longevity. Sorry koolpc but just just cbf with cement in this scenario.

 

[Participant]

Not sure why you wouldn't put a cavity closer in then stick down a window board, its hardly a big job. Even a bit of insulation in the cavity before the window board goes in helps with the thermal bridging and reducing condensation...seems like a no-brainer.

Thanks. Are you saying add more insulation to the cavity? What kind should I use?