as above really. I’ll be laying a new chipboard floor over some old joists, some of which have been replaced and now it is all insulated.
The joists are not 2.4m spaced to line up with the join on the short ends. How do i resolve this?
I guess I can always cut the boards and line them up on a joist and screw down without a t&g joint.
or maybe I put a load of noggins in where the joins are to support – but these will then be 90 degrees to the join and will be a right pain now the insulation is in between the joists!

errrr, run the boards across the joists cuting them so that end/end joints are on the joist.

I guess it just won’t be quite as solid / squeak free as it won’t be a t&g join.

Don’t worry about it because the joint will be supported by the boards in front and behind?
You are stagging the boards “brick-style”, right?

my bedroom ^

BTW they werent laid like that, they were staggered.

how wide is your room?
how many end/end joins do you have across the room?
The T&G joins go mid-room, and you cut off flat at the edge of the room.
Very occasionally you might have a flat/flat join so as not to waste too much wood but it wont be a problem if you screw it down well – you may even want to make sure there’s a little gap as it is the rubbing that makes a squeak

Yep, I will indeed be staggering the boards. of course, now I see – the t&g on either side will help hold it all together anyway and the joint will be over the joist. Job done.
thanks.

The room is about 5m wide so I guess there won’t be too many joints anyway, and I can hopefully cut most of the boards at the end the meets the wall so most joints will be t&g anyway.

Assuming that you’re laying 2400 x 600 t/g chipboard over joists…and that you’re laying it so that the longer sides of the sheets are perpendicular to the length of the joists…

The idea of t/g chipboard is that you can “hang” the joins between the joists, so don’t worry if they’re not lining up. Stoner’s idea is fine if the chipboard is not t/g but if it is, then it seems like you’re creating a lot of work for yourself. Also, butt joining chipboard on a joist is a recipe for squeaks in the long term.

Other tips:
drill pilot/clearance holes when you lay the sheets down
A bit of PVA/expanding foam in the joins just before you screw the sheet down doesn’t do any harm
Before you lay the first row, make sure you measure across the room so that you don’t end up with a really thin rip for the last row.
Make sure the joists are as clean as possible if they’re old. Don’t worry about removing old nails, just bang ’em in flat.
Don’t use nails, use screws.

Oh…and a good drill eh Stoner? 😯

like stonor said you should be able to land the joins on the joists until you need a third board when you might miss. If that’s the case then it’s OK to fly the join over free space so long as its T&G. If you’ve got lots of unsupported joins then you could consider 22mm boards especially if the joists are >400mm spacing. If you use the offcut from one end to start the next row then you should have minimal waste with staggered joins.

Don’t forget to glue the joins and screw the floor down with oiled caberfloor screws (from screwfix). All that squaeky chipboard nonsense is the boards rubbing up and down nails.

I did that lot with a crappy Homebase drill 🙂

Butt joining is OK if you leave a gap. But I agree not ideal.

right then. I’ve got 22mm t&g board so that’s easy, I just lay across without worrying about lining up the joint on a joist. winner!

I’ve got the floor-tite screws from screw fix. Are they the puppies?

really drill pilot holes? I thought most of these modern screws in combination with an impact driver meant we could ditch that step?

Almost… you trim the first board (at the wall end) to align the end onto a joist then work across the room from there. You do the same on the second row using the final offcut from the first to land on a different joist to get the stagger.

oh, and out of interest, what length screws for 22mm board? are 45mm ones suitable – they are the ones I’ve got ready, but I can always get different ones.

I’ve just checked it is the MDF-tite 45mm screws I’ve got for the job.

We used powerdrive board screws (screwfix part 13932). They are covered in a lube which gets them into 22mm caberfloor without pilot holes. Ideally you’d want 2/3rds of the screw into the joist so 66mm but we used the 1″3/4 you have and they are fine. Caberfloor website gives the screw pattern to use.

Oh and the pilot hole thing might be more about joists. Where we fitted new suspended floors no pilot holes required. When fixing to 100 year old oak joists it might be a wise move.

the joists aren’t oak they are just older (1930s).

thanks for you advice Digimap.

45mm screws are ok though technically the depth of the screw to the sub-floor should be 1 1/2 times the thickness of the chipboard. So, 45mm is ok for 18mm chipboard if you get me. TBH, 2 1/4 inchers would be better but I don’t see you having a major problem. Screwfix turbo-gold are good screws. SPAX are also good (sold in B&Q). WURTH are the best (not so readily available).

As for pilot holes, no, they’re not essential but if I’m doing it for a client, I tend to drill actual “clearance” holes – which are the thickness of the shaft of the screw. The way a screw binds in chipboard is different to the way it binds in plywood/solid wood/mdf. With chipboard, it’s more about the fix into the sub-floor/joists that’s important which is why I’m recommending 2 1/4 inch screws (No. 10’s minimum). The idea with clearance holes is that the screw flies in through the chipboard and the head (with a good torque setting on your drill) sinks flush and holds the board in place.

If you have a separate plug-in cheapy drill, you can use this to drill your clearance holes. Try to stagger the screws i.e. 3 across one joist, 2 across the next, 3 across the next and alternating this across the rows of board too. It might seem a long way round, but if you do your clearance holes, then “stand” the screws in the holes and then go with your driver, you’ll be surprised how quickly you motor along once you get into the swing. It can be frustrating sometimes waiting for the screws to get the initial bind in chipboard…and sometimes they end up going in a bit “wobbly”.

Sorry, I’m getting far too anal about this now. If there’s anything else you need to know, ask.

what about perimeter noggins? is this important?

Ummm…no I don’t think so. If you’re using 22mm, there shouldn’t be a great deal of flex in that board anyway. It’s not essential, but if you really want to do it, then it’s not going to do any harm.

Just thought of another thing…mark out any pipe/cable runs as you go (even if they’re under the joists)…you never know when you want to get at them and it helps any future occupier (not your problem I know…).

EDIT: The idea is that you use the off-cut from one row to start another. Don’t worry about the stagger having to be half way along the board…as long as it’s more than 500mm away (but don’t kill yourself sticking to this rule), it’ll be fine. Also, if the offcut you use to start the row only hangs on one joist, then this should be discarded. Obviously, keeping to the stagger rules, the last thing should not happen, but never have two hanging joins in adjacent rows of chipboard between the same joists.

good plan with pipes and wiring. I’m doing drawings as well for those 😉

Also, lay the first two rows loose (but tight together, just not fixed) so that you’ve got nice clean joins. If they go out of alignment, it’s a pain. No major probelm if it’s only a few mm but it don’t look purdy.

what about perimeter noggins?

If you don’t put them anywhere else, put them where there is an unsupported joint.

Perimeter noggins probably overkill with 22mm like DD said, especially since 1930 joists are most likely about 18″ spacing. The one exception would be in any doorway or entrance as foot traffic and wear is going to be high and an unsupported edge might sag over time.

Another good idea (as a DIY’er) would be to dry lay the whole thing first. Then part lift it and work your way across final fitting with the glue. Mark the joist positions on the wall before you start then when the floor is down and glued a quick line up with a laser (or string) makes getting the screws in really easy and accurate.

When fitting uses little wedges between the wall and the first boards (we used window packers). With the wedges in place you can wallop each row of boards to close the joints without losing the expansion gaps. When walloping use an offcut mated into the t&g and hit that, not the actual board.

I don’t think there’s much more to know. Don’t forget to post some piccies!

I don’t think there’s much more to know.

Nope, I think we’ve done it to death now!!

No excuses Sam!!

Thanks guys. I’ll definitely get some pictures to show you the end result!. assuming I don’t make a pigs ear of it of course 😉