Thread: large ceiling joins need filling - HELP!

another few questions...
I have not back blocked as the roof cavity at this end of the house is
very low and it would mean that I will have to remove a heap of roof tiles to get to the ceiling plus remove all the new insulation I just did!
Do I really need to back block what I have done?
Have only used 3 sheets as you can see and the rafters are 500-560mm spaced.

Stud adhesive & screws.
I have noticed that some of the daubs of stud adhesive have come away from the ceiling at the edges which makes me feel a little uneasy and question the rest of the spots. I remember having read somewhere not to put the stud adhesive on the ends (after I did the work!)
Now I know that it says you should not screw or nail where the adhesive is but this relates to when the sheets first go up and the adhesive sets yes?
As the adhesive will suck up the sheets as it dries and may cause cracking around the screw/nails.
So can I go and screw the sheets to the rafters for peace of mind when all is set and dried?

Yes you can screw those sheets, however when the sheet pulls up tight the stud adhesive could cause a blister in the sheet. If that happens just cut it out and patch.

With those gaps, you can prefill them with base coat and when set scrape the excess back, be carefull you do not fill the recessed edge, just to gap.

Only use paper tape, only use paper tape only use paper tape. Get that? do not listen to the inexperienced people at Bunnings that have never had to fix a house full of joins that have cracked from using fibreglass tape.

Cheers Rod

Rod hi,

thanks for the tips
I'm actually working on it now! Went and bought a cordless drill.
As when I first fixed the screws I only had my electric drill (usingh the special plasterboard screw bit) but it had too much torque and was snapping off the heads.
So I am unscrewing, pre-drilling and rescrewing using the ratchet on the cordless. Done about half now and it is working well.
Have noticed that the stud adhesive hasn't worked in quiet a few spots. Not sure why as I did it without a chance of the stuff going off.
The only reason I can see is that maybe the sheets may have been a bit dusty and therefore spoiled the contact.

You say fill the gaps with base coat, is this the same as the bucket of Ready Mix QuickCote RG4000 that I am going to use for the jointing and fixing the cornices.

I was going to use selleys gap sealant flexible due to the fact that it is flexible, does it matter.

If I do use the QuickCote shall I mix some salt with it (got that one off your site!) so it will set quicker?

again thanks for the help

First the salt will not help the QickCote go off as it is a drying compound not a setting compound. I would not recommend this for putting up cornice! Nothing beats cornice adhesive, you can buy it in a 2.5 kg bag or 5kg.

Filling the gaps will the QuickCote will work but you will be waiting a long time for it to dry before being able to scrape back and do the taping. DO NOT fill the gaps with a flexible sealant. The plaster used for taping will not adhere properly to the sealant.

The best thing to fill the gaps is any setting type plaster that will go off reasonably quick, will scrape back, and will allow the taping coat to adhere. Rembember scrape back as soon as it has set. do not wait for it to dry as it will be tooo hard.

There are a few reasons the glue has not taken up. The 2 most common is, 1st, that the daubs of glue have just been wiped onto the joist, (they should be like a walnut about 20mm deep at least. The 2nd is that when positioning the sheet the glue is wiped off the joist. the sheet should be positioned againts the rebate or the wall on an angle then pressed up to the joist. Any sliding of the sheet to correct the position will wipe the glue off the joist and break the seal.

To fix screw at 300mm centers along the joist.

Personally I do not like the pre-mixed type products except in the middle of summer where they will dry much quicker. They also shrink a lot more than setting type products, and are not so good for filling big gaps in joins like you have.

When using these products in summer we still go around the job and pre-fill any gaps wider than 2mm with a setting plaster. The reason being that the drying compound when filling a wide gap can take up to 48hrs to dry becuse it is so thick.

Also as well as using glue you should have a row of double screws throught the center of the sheet.

Good luck with it.

Cheers Rod

Rod hi,

had to get on with it so I have been using the QuickCote to fill the gaps.
What I am doing is not trying to fill in one go but create an edge on the edges of the gyprock to basically narrow the gap, it seems to be working.
I'm letting it dry for around a day then to do the next fill.

I think I'll get the proper cornice cement as a quick set seems the way to go.

Stud adhesive. Did as the instructions said, wallnut daubs and I also used a sheet lifter. The sheets went straight up into place.

Any question for ya!

I have a small sheet that fills a staggered section 1200mm x 280mm.
Now where the join is it has a diff of say 3-4mm.
I have evened this out with QuickCote with the plan to then go with the tape
over the top. I just thought no point trying to tape with that edge as it would prob damage/tear the tape. Is this OK?

cheers mate

cornice cement?

is it a quick enough set that I don't have to use nails to hold the cornice in place
or would you rec to still do this?

No need for nails if the mix is the right consitency. Not tooo thin but not thick and dry.

Cornice adhesive = cornice cement (for us oldies in the game).

Prefilling the butt join was ok to do

Cheers Rod