patching ceilings?

[EMistral]

Hi guys,

this might sound a silly question but here we go!
I am going to have a ducted heating installed and the company doing the job will remove the 2 old wall furnaces.
These furnaces are fixed on the wall and through the ceiling up to the roof
The company will remove them leaving a hole or square in the ceiling.
The stupid question is: how to patch that? how would you proceed?
The holes/squares will be probably 15cm x 30cm

Thanks for your help
Eric

[namtrak]

Is the ceiling made of plaster?

Assuming so then, glue 2 pieces of plaster together. One slightly bigger than the hole and one slightly smaller than the hole. Then from within the ceiling glue the piece into the hole. This will leave a small gap between the hole and your insert which you should be able to patch up with base coat and top coat.

Cheers

[EMistral]

I see what you mean
The ceiling is made of plaster

First: what type of glue do you use to glue the 2 pieces ?
then: what do you mean by base coat and top coat? what product do you use for that ?
Thanks

[mic-d]

choose appropriate patching material eg gyprock or fc sheet. Cut one square out for the patch and holding it up over the hole, scribe a line around it. Cut out the hole to the line. Dust off inside the ceiling around the hole to allow glueing a backing sheet. Cut another piece about 40-60mm larger that will be the backing sheet. using liquid nails, glue the backing sheet over the back of the hole. fit a screw to the middle of the backing sheet to allow pressure to be applied and allow glue to dry. glue in the patch making sure it is flush or just below the surrounding ceiling. Topcoat and sand the gaps to feathered edge. wipe the dust out of your eyes and paint.

Cheers
Michael

[namtrak]

I see what you mean
The ceiling is made of plaster

First: what type of glue do you use to glue the 2 pieces ?
then: what do you mean by base coat and top coat? what product do you use for that ?
Thanks

Liquid Nails will do.

Base Coat and Top Coat are 2 plasters. Base Coat holds the joins together - be careful with base coat because it is very hard to sand back. Top Coat is a finishing plaster which is easy to sand. You wont need much, but even if you get 1kg buckets, they come in handy patching up holes and stuff

[EMistral]

I am going to be a bit more silly:
I am guessing base coat and top coat are the type of material.
what brand would you recommend?

[namtrak]

The cheapest - there's only a couple of choices (Im using Boral at the moment). Head along to your nearest hardware store and ask them for the smallest amounts of basecoat and topcoat that they sell. Top coat generally comes pre-mixed, base coat you need to mix yourself (but work quickly because it dries very fast - and remember to wash you tools)

[silentC]

You can get a total jointing compound, which I wouldn't recommend for a complete job but which I'd guess would be OK for patching. I've used it and it sands like top coat. Just saves buying two buckets/bags...

[HavinaGo]

Eric,

a) watch the different thickness of gyprock/plasterboard. I've a place with slightly thicker plaster than the modern stuff (10mm) and that means setting up the front face of the fill piece needs to be done a little more carefully.

b) Given my inability to feather an edge nicely, I've found it easier to remove the paper from the front face of the pieces along a join to create a recess. ie create a rebate that will be filled with jointing tape and plaster to leave a join level with the front face.

c) reinforce the joint with tape. There are other discussions saying paper tape is best, but I've used the self sticking fibreglass stuff OK

Have fun

[EMistral]

ok I see the picture
Now once you have glued your 2 plaster sheets and created this patch and glued the backing sheet in the ceiling so that it leaves only a small gap between the hole and the plaster, how do you apply the base coat and top coat ?
I mean, do you apply the base coat on the side of the plaster boards then glue the plaster sheets (backing one + the other one) on the ceiling ?
or you glue them first them using a trowel or any type of tool, you apply the base coat in the gap between the patch and the ceiling?
It might not be clear for a question :)
So a simple draft of what I think is better
I have attached a sample word doc to described what I think you guys are trying to tell me
on this drawing, where would you apply the base coat and top coat ?
Thanks

[mic-d]

Really if you've scribed the hole to match the patch, the gaps should be neglegible so as not to need a base coat, just a total joint cpd. And because there are no shear forces on the patch since it is only attached to the sheet and not to a wall stud, you shouldn't need tape either. I've done heaps of patches by this method and never had any cracking.

Cheers
Michael

[namtrak]

Nice Picture, thats the idea though.

Mic-d is probably right about the base coat - I get carried away with this sort of stuff.

Whichever way you go, you apply the base coat, top coat after the glue has dried on your patches. You apply the base coat with a clean trowel edge to say 2 inches wide over the crack as flat as you can make it. Once it's dried, scrape off any burrs and then apply the top coat to say 4 inches wide, sort of feathering it over the edges. Once this is dried, sand and paint and in your in the good books.

I think a total joint compound is probably a little more elastic than top coat which has no elasticity at all, and is therefore probably a better solution if your not bothering with the base coat.

[silentC]

Mic-d is probably right about the base coat
I'd just like to point out that I mentioned it first :p

;)

[namtrak]

Yeh, but yours was with a SilentC - so I missed it. Speak up next time :)

[wombat47]

One more hint - if you are mixing your own compound (adding water to dry stuff) -

If you don't make up enough and need to make up more, wash all traces of first mix from container and tools first. Otherwise, the first lot will make the second lot set very, very quickly.