The room is an extension, single story with a flat roof (yes I know!)
approx size is 6.6m * 5.3m (with a corner cut out) the joists run across
the short edge (there is a RSJ from the corner of the cut out to the
short wall to which the joists 'join'). There was no insulation at all
hence it was so hot/cold, I've almost put that right.
The question si as the joists are 15" centres - not a divisor of standard
board sizes, which way to run the boards and should I/ do I need to nog
the joins/edges of the boards?
My feeling is I need to put quite a bit of wood in there to support board
ends/edges to prevent sagging.
As a follow up question 9.5 or 12.5mm board?
Have a good week-end
The book I'm reading says put 3" by 1" battens perpendicular to the joists,
correctly spaced for your boards, and shimmed if there's any unevenness.
I havent tried yet myself,
I wonder what those who have will suggest..
(the book says the hardest thing is taping over the joins)
The alternative is to cut the boards short to suit the joist pitch.
Using 2400 x 1200 boards you're cutting 120mm off the length of each
board which is an easy task with a stanley knife
I'd recommend using 2400 x 1200 boards as it means fewer joints, your
35sqm with cropped 2280 x 1200 boards comes out at about 13 boards
whereas using 1800 x 900 mm minis comes out at 22 boards or a lot more
If you want to keep it DIY then use taper edge boards and don't skim. I
view 9mm as little better than cardboard so would use 12.5mm but you
will need help to fit them.
I wouldn't add extra support for the tapered edges (which are running
cross joist) but would leave a 3mm gap, scrim tape and be generous with
the board finish jointing mix to fill the gap and add strength.
The end joints aren't tapered and will be (slightly) noticeable but you
can save the cost of a plasterer if that is important.
FIVE TV's superbright logo - not the DOG's, it's bollocks
More joints, but heavier boards. I got 1200 boards for my ceiling, and after
lifting one, I changed to 900mm, using the 1200 for walls. With assistance
1200 would be ok. 9.5mm at 2400mm board may be too bendy for single handed
One or two large T squares to support the boards are almost essential, 2x2
with a length of floorboard for the top bit is what I used, a few mm more
than room height.
Thank you for that (and the others who have replied) that sounds like a
doable job - I've got a favour or two to call in when it comes to the
I am trying to avoid a plasterer for various reasons not least I can't
strip the room to make access easy for them.
That's quite doable, just leave a 5-7mm gap between the boards so you
can squeeze lots of plaster in to reinforce the joint.
Re the boards, you'll need asssitance lifting them, though it is
possible, albeit a little awkward, to do 6x3 9mm on your own, using a
dead man. I'd suggest 2x 1/2 for it rather than 2x2, makes it easy to
bend into position.
You'll not need to nog the joints. Put the length across the joists and cut
to length (you'd lose 4" on an 8' board) to put joints in the middle of the
I would use taper edge boards (thickness to suit fire regs, 9.5 would span
ok) and just tape and fill the joints.
Firstly, if you've never plated a ceiling before, you aren't going to be
able to get it good enough to just tape the joints, it will need plastering.
15in centres is slightly odd as they are normally 16in, but no, you don't
need any extra support or noggins.
You're better off using 6X3 plasterboards and get the thinner ones as they
are easier to handle, and they need to be fixed pale side down.
They have to be jointed in the centre of a joist on the shortest edge, that
is to say, the edge that is 3ft will be fixed, the long edge won't, and
obviously you will need to cut them so that they land on a joist.
If the joists are thin, you might want to get some 2X1 batten to add a bit
of extra width to the joists that the boards meet on - you won't need it on
all the joists.
Before you start, mark a line on each wall where the joists are, and use
screws rather than nails to affix the boards.
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