plasterboarding garage ceiling


As title says....currently it is open with joists at 24 inch centres.If I use mainly 8 x 4 9mm plasterboard sheets, I guess the long sides will butt up to each other "longitudely" in the centre of every 3rd joist, as well as all along each edge, and I can nail 'em in place. However this leaves the ends ( 4 ' ) of the boards fixed by just the three places where they contact the 3 joists at right angles. ( if you see what I mean! ) Would this be acceptable, or will I have to fix extra wood pieces across joist to joist where thes board 4 foot ends are? I do Intend to have it all plastered afterwards. It is not going to be used as a "room" as such, just that it is very cold and hard to illuminate at present and I use it as a workshop quite a lot. Alternatively, any suggestions of other ways to achieve a good result - EPS Insulation sheets for example??
Also, will "external white masonry paint" be ok to use on the "breeze block" wall? The wall is also the house wall ( internal in other words) and shows no sign whatsoever of damp/ lime etc, ......unlike the opposite side of the garage which is single course common brick to the outside. Is there any special preparation I need to do before painting, apart from obviously brushing well to remove loose chips / dust etc. TYIA
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I would secure the sheets with drywall screws instead of clout nails, seems to be better, and just as quick with an electric screwdriver. The edges of the sheets need to be secured, so you need timber doublers at the back of the joints. If you nail the sheets up they will have to be very secure! If you screw them up they can almost just be attached to the sheet before it goes up, and to be honest i have used a bit of plasterboard stuck on with adhesive where it was a tight corner!
I dont think it is really necessary to skim the surface, not for a garage cieling anyway, you can tape the joints and get a special primer.
That advice has probably saved you a few bob!
Oh and get a step up the right height so you can balance the sheet on your head whilst you put the first three or four screws in.
Good luck with the job.
John

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Just had our garage built over with an extra room. Check your building regs cos I had to have ours insulated above,`6mm ply and then 12mm plasterboard, finished off with plaster skim to provide req'd fire proofing.....pain in the ar*e I know. Hopefully your building inspector will not be as stringent...... Eric :-)

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And/or get a couple of bits of timber and make a " T " about half an inch taller than the height of the underside of the plasterboard. Then you can stick it under and give it a bit of a kick to hold one end up whilst you work on the other.
Steve
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Thanks for all the advice folks....have decided to go with 15 mm board to avoid having to fit noggins. Think maybe I will skip the skim coat, and tape neatly at the joins, - what is this special primer called ? Don't intend bothering the building inspector ( its not a habitable room after all, just a garage.)

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The primer is called Gyproc Drywall primer, also you need the correct tape, not just plasterers scrim, and the correct filler.
You should vbe able to get these from your local builders merchant (or B&Q?) but it would be worth looking at British Gypsums website, and specifically the page http://www.british-gypsum.bpb.com/immediacy-1446
Justa thought though Tim, make sure you dont shut off all ventilation to the roof space, or you will finish up with a timber decay problem instead of a nice clean ceiling!
John

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Thanks John....what is the correct tape then?? do you mean filler to use in the joins under the tape?? Also, good point about the ventilation, could / should I put in some ventilator grills in the actual ceiling, or arrange some airflow from the actual roof space somehow? TY sorry for so many Qs

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The filler, tape, and so forth are all described on British Gypsums website, and they used to produce a book** on good practice. If you go to a good builders merchant rather than a DIY store, they will probably be able to get these for you. You ca get a "proper" taping knife, but i just used a broad bladed filling knife when i did some of this work. There is a "proper" sander for drywalling (i.e. not skimmed!) but you can do with a sanding block if it is a one off job. If you smooth the filler carefully there wont be much sanding. If you watch professional dry walling people working, they are incredibly fast. There are probably DIY books on this as well, but it isnt a great score really.
** I just checked, and the BG "White Book" is now on line, so you can read up about the tape, filler and techniques.
This is at:- http://www.british-gypsum.com/whitebook.htm
Ventilation, every job on its merits, every building and every use makes it a bit different. If its a flat roof with plasterboard on the underside of the joists, it wont need much. Perhaps some small plastic push in ventilators in the plasterboard.
If its a big pitched roof, you need more. perhaps a vent in an external wall?
If you are going to have the car engine running in there for very long it needs to be thought about. If there is an enclosed floor above, the ceiling needs to be fireproof, so the ventilation needs to be other than from the garage.
You could ask your council building officer, a local architect, or a good local builder. If he isnt good you may get poor advice!
John

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