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

Participant

Participant

Participant

Caporegime
Joined
13 May 2003
Posts
34,515
Location
Warwickshire
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...

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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.
 
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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. If it’s bare wood then you either need to make plugs to hide the screws or use oval nails or something like that.

I’ve done it two ways recently with solid oak sills which I’m not painting and don’t fancy making plugs for. I got it level with glazing packers. Then CT1’d the packers down. Then stuck it down with large dollops of CT1 on top of the packers. That’s one way, second way is the same with the packers but I used PU adhesive foam instead of CT1.
 
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I had some sort of drip tray over the breeze block. As the existing sill was wood it took up quite a bit of room, the new ones are PVC and about quarter the thickness so I've had to chuck some plywood under it and then packers to level it.
 
wouldn't you put some insulation across the cavity beneath the sill - folks had a casement window (ok slightly different) done recently.
(that's the proverbial cavity wall fill too ? which they had too. )
 
I've just dealt with a couple of sills like this. I put plastic cavity closers in to seal the cavity which for me was the key point as I don't want the sill and its sealant being the final damp/draught excluder.

After that its down to preference and size of the gap to be filled under the window board (sill). In one case I used finishing plaster and another mortar as a base coat and then top coat plaster. In both cases I fixed the window board down by brackets underneath and down the wall, however any form of plastic/wood packer or construction adhesive would have been fine.
 
Thanks all. Had never heard of cavity closers but they sound like a good idea.

Mason- said:
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.
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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.
 
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.
 
Pack the window board level.
Lift it off foam on the brickwork, lay the window board down and weight it with a few bricks.
Low expansion foam is best.

www.toolstation.com

Soudal Genius Gun Low Expansion Insulation Foam

• Quick setting • High insulation values • High linear yield (more metres) • Reusable for up to 6 weeks • Interior and exterior useProfessional quality insulation foam with high insulation values, both thermal and acoustic. The foam has minimal expansion, providing a greater linear yield...
www.toolstation.com www.toolstation.com
 
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.
 
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Participant said:
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.
Click to expand...

I'm thinking of the same route as you when I replace mine. I may just double / triple up on the plasterboard for packing, using adhesive foam to stick down, then adhesive the board on top.
 
Participant said:
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.
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I wouldn't bother with cavity closers. It's not like it is super airflow friendly as it is. I wouldn't even remove the wood Packers tbh.

I wouldn't glue new packers with foam either as it's a messy stuff. If required stick them with whatever you have available (I used caulk/gripfil or something just to stop them wobbling off) as the foam will be sufficiently 'structural'.
 
Participant said:
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.
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Well, that, to me, is the bodge way of doing it sorry.
 
koolpc said:
Well, that, to me, is the bodge way of doing it sorry.
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It’s a perfectly acceptable and quick way of doing the job that will last years and nobody will know the difference from the outside. It’s not the traditional way of doing it but modern materials open up a myriad of new methods.
 
Participant said:
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.
Click to expand...

That will be fine. I did similar ish in one of my rooms but didn't take the board off just filled it with expanding foam pre plastering.
 
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.
 
gingergundog said:
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.
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Thanks. Are you saying add more insulation to the cavity? What kind should I use?
 
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