Fill gap between brick wall and ceiling

[unionworkeruk]

I have stripped the plaster from the walls as I want to clean up and expose the brick work and wood in the walls.
I will also put a plywood ceiling screwed to the joists through the existing plasterboard.

The problem is that however the ply is cut there will still be gaps between ply and bricks. I am not too worried about the gaps when finished as they will be relatively small.

But there is about 100 years of dirt up behind the plasterboard which since the plaster was removed can now fall through the gap between the plasterboard and brick and down through the ply and brick.

I am thinking I should seal the gap between the brickwork and existing plasterboard which will stop any dirt dropping through. The problem is that the gaps are up to 5 cm in part with nothing behind them for anything to stick to.

Any ideas ? Thanks

 

[scratchyrat]

Expanding foam?

 

[foxhole]

So you want to create a fire hazard with a ply ceiling?

 

[unionworkeruk]

Is a plywood ceiling any more dangerous than wooden panelling, waxed pine floors or hundred of books in wooden book cases or even many sofas and armchairs ? Or are you saying any additional wood in a room adds to the danger in the case of fire ?

I understand you can buy fire resistant ply though.

 

[Blagard]

Cut some expanded metal lath into strips (at least twice as wide as that gap) and slot it behind the existing ceiling, then use a bit of string or similar to hold the lath down onto the ceiling while you squeeze some bonding undercoat into the lath. Once set, especially if you left the bonding back a bit just cut off the bits of string and use some finishing plaster to level up to the ceiling.

 

[foxhole]

Ceiling protects the floor above in a fire, making it more flammable is not a good idea, if you wanted too board then add a layer of fireboard [fire resistant plasterboard]to seal right across the existing ceiling closing all gaps.

 

[opps]

I second the expanding foam suggestion. Spray the area with water first to aid adhesion and curing. Cut away the excess when cured.

With regard to fire risks, it may be advisable to use intumescent foam. In the event of fire, it will expand and ****** the ability of the flames to shoot up the gap and set fire to the flooring above.

 

[Blagard]

I forgot to add to my suggestion that on the wall side the odd nail or staple will stop the expanded metal lath rotating out of the gap when you pul down on the string. I have used this method on holes where cutting out for insertion of a new bit of plasterboard is less practical. I would use it on your scenario as I know it works even on holes in walls!

 

[unionworkeruk]

I second the expanding foam suggestion. Spray the area with water first to aid adhesion and curing. Cut away the excess when cured.

With regard to fire risks, it may be advisable to use intumescent foam. In the event of fire, it will expand and ****** the ability of the flames to shoot up the gap and set fire to the flooring above.

The only problem is that there is nothing for the foam to hold on to as it is a gap between the plasterboard ceiling and a wood beam a couple of cm away. If I spray it on the wall it will drop or dribble down , behind the plasterboard it wont reach the beam but drop before reaching it I need something to span the two.

 

[opps]

I still think the foam will work.

Won't the ply run closer to the wall than the plasterboard?

Insert the nozzle about 5 cm above the plasterboard. The first run will expend, some will slump down and not bridge but you can then wait for it to cure and apply more.

Another method would be to cut some thin strips of hardboard (etc). Coat it with polythene dust sheets and then drill as series of holes in it. Then tack it to the ply around the perimeter, following the wall as close as possible. Then insert the foam nozzle into the drilled holes. When the foam has cured remove the hardboard, the foam won't stick to the poly dustsheet. (I hope that makes sense, sorry, have just woken up)

 

[unionworkeruk]

Thanks I dont want to fill the gaps between the ply and the wall as the ply will be stained and the brick left exposed. Any filler will show. Thats why I want to block the gap between the plasterboard and brick even though there are larger gaps. That will stop any muck falling through from the roof cavitity above.

I will give the foam a go and use some hardboard to hold it up while it sets.

 

[unionworkeruk]

I have found a solution - foam backer rods in different sizes which I can cut to the length of the gap, wedge in and use Gripfix to fix to the wood on one side and the edge of the plasterboard on the other. That then gives me something solid to spray behind if I need to us foam filler.


https://www.dortechdirect.co.uk/sealants-adhesives/backer-rod.html

All the advice set me in the right direction Thanks