plasterboard sizes

[Richard C]

12.5 + 25 = 37.5 so even if you use the shortest screws under the 3x rule (38mm) you will snub the point; that’s assuming your 25mm battens are actually 25mm. Screws at 400mm pitch is way too much for 12.5mm boards, on what bassis did decide that even 300mm pitch was overkill let alone 400mm; your boards will eventually bow & run a serious risk of failure in the long term.

I’ve got a strange feeling about where this thread is going, I suppose now you’re going to tell me you’ve calculated it! I never have but British Gypsum almost certainly have; I would be very interested in seeing your calculations &, yes, I would understand them. You ask advice & then start going all strange; your not geraint’s alter ego are you with the crap he’s coming out with at Alistair? Is there some trolling going on here? Bit tired of this sort of stuff, it's really a waste of my time; my last words are get on with it but buy yourself a hard hat.

 

[joinerjohn]

Hmmmm , so it seems someone is hoping to gripfill some battens to a concrete ceiling and put a few screws and rawlplugs in and hopes it stays up?.
I don't think so. Any spread worth his salt will tell you, that you'll need battens solidly fixed to the ceiling (either plugs and screws probably every 400mm minimum) (or Hilti gunned every 300mm minimum) 12.5mm boards are usually specified for ceilings. I have yet to see an architect today specify 9.5mm boards for ceilings.

 

[jollatine]

No, I'm not messing with you, I'll take your advice and go at 300 centres. I went on this forum to listen to your advice and will use it. The only calculation I made was how much 2 x 1 I needed (I'll need more). It is 25 mm deep, so I wasn't too concerned about the ends of the screws being snubbed as the skim coat from before will take it.

The issue with gunning to the ceiling is to overcome another problem. The ceiling is made of a beam and block type - I'll do my best to explain: There are some solid concrete beams and in between are clay like hollow tubes which run between them. The next layer is my ceiling which is about 10mm concrete and then skim coat. Previous attempts to drill and rawlplug to this is fairly fruitless as if you hit a cavity (which happens 9 times out of 10) there is no hold. So the combination of nail gun and gripfill was the solution. Obviously, your time taken to contribute IS appreciated. I'd rather get it right before hiring the nailgun or have a sheet of plasterboard landing on my head.

 

[Nige F]

hi mr gumby,
as a pro we do not use 8x4 sheets to save time or money!!!!
it is because thats the specifications on the drawings we work from, and is more professional.

never seen the size of the board being specified... and please tell how it is MORE professional...

C,mon even if it was 2 years ago, experienced spreads & builders still “talk” in old money. It’s 2400 x 1200mm in new money as far as specs go as I’m sure you’re aware; unless your being pedantic

not pedantic.. but never seen a spec with the size of board. the reasons of the smaller boards are well evidented... if that is a word...

No it`s not a bloody word it`s like evidenced - tasked etc. you should of said well documented

 

[Richard C]

I'll take your advice and go at 300 centres.

Read my posts again, I didn’t advise 300mm centres; British Gypsum specify a max 230mm, I never space screws more than 200mm apart

It is 25 mm deep, so I wasn't too concerned about the ends of the screws being snubbed as the skim coat from before will take it.

You still only have a maximum of 37.5mm if you use the correct (minimum) 38mm screw, your 1/2mm long. If you bind the tip of the screw on the concrete, there is a good chance the head of the screws won’t end up just below the plasterboard surface where they should be. There is also a chance that the PB is not pulled up flush with the battens, virtually hanging on the screw heads or even force the battens away from the ceiling.

 

[theoldun]

Jollatine
With respect your first post was very misleading, as it would appear that you wished to tack a traditional plasterboard ceiling over timber joists. You then go on in your next post to say that it is a solid deck of pot and beam that has been floated and set, which makes us ask the question, why do you not over skim the existing?
Without going into to much detail, in the 50s pot and beam were usually installed in flats or houses built for the local council. There were two ways these were done, and providing the beams in your deck are at approx 325 or 550mm centres all as present day block and beam then you can tack a plasterboard ceiling if required. The pots are hollow clay terra cotta with internal stiffeners. When we were looking for the start years ago if we saw pots on the job you drove past as they often used to be used for the inner skin of cavity walls. They were a nightmare to lay. You can fix to them with spring toggles or hollow ceiling anchors.
This is how we would do it. Assume your beams are at approx centres as given above and that they run the short span of 1700. Run battens 90 degree to beams, increase you batten size to 5 number 32x50, one against each wall and inters at approx 425 centres, run a heavy bead of sticks like sh*t along top of batten and plug and screw (brown plugs, 5.0 gauge screw) to each beam, On the three inter battens cut 300mm long length of builders band and fix over top of battens into beams two screws into band each side. Scribe your boards into wall and thicken up your skim coat at top of wall to give support to edge battens. If you are still worried chop 5 angle brackets each side into batten and wall. Use 12.5x900x1800 plasterboard and 38m drywall screws. At 425 batten spacing and 12.5 boards no need to nog long edges of boards. She will not go no where. All the best.
We do not like to criticize other members posts as after all, we are here to help one another out , but we are inclined to agree with what geraint has said. In all our years of pricing drawings, specifications and bills of quantities, it is very, very rare for the sheet size of plasterboard to be given. Thickness, yes, i.e. 9.5, 12.5, and 15mm.
In 9.5 boards there are 4 different sized boards, in 12.5 there are nine sized boards, and 15mm five sized boards, so we do not understand how any one can say it is more professional to use 1200x2400 as against a 900x1800 or a 1200x3600.
The reason why 1200x2400 are mainly used is because labour wise and material wise, it used to be the most cost effective way of doing ceilings, how ever, on new builds to comply with both fire and acousticsand to omit noggins it is now more economical to use 15mm first and ground floor.
oldun