22mm chipboard flooring T&G short side joint to land on the joist or not.

[chrismac]

I am getting ready to lay 22mm chipboard flooring, my plan was to cut 400mm insulation board for under floor insulation, the 400mm ties in nicely with the insulation sheets but the spacing of my floor joists does not lend its self so good and the flooring joins dont land on the joists, I will be glueing the joins, the joists are approx 65mm wide,
After lots of reading up, there are very mixed ideas of if the joins need to land on a joist or not, I could reduce my joist spacing, I would probably end up needing 2/3 additional joists for the losses,

I am interested to hear the thoughts of the group, am I over thinking this, or do I need to either add supports to the joins or reduce my joist spacing.

Thanks

 

[Welderpaul]

I looked into it when i did my loft conversion a couple of months ago because I ended up with a odd joist centres to work around existing trusses as my structural floor had to be in first before cutting out the braces. I let the board short sides join off the joists and there is no flex in the floor.

As long as you stagger the board joints, the T&G supports each long edge next to the joint. I glued every joint, and glued to the joists.

 

[chrismac]

I looked into it when i did my loft conversion a couple of months ago because I ended up with a odd joist centres to work around existing trusses as my structural floor had to be in first before cutting out the braces. I let the board short sides join off the joists and there is no flex in the floor.

As long as you stagger the board joints, the T&G supports each long edge next to the joint. I glued every joint, and glued to the joists.

Thanks for the reply, this will save so much headache, I laid a few out tonight, dry fited and there is very little flex when I walked over them,

 

[gaz1]

glue and stagger the boards dont go right up against the wall its better to use a 5mm spacing at wall sides

what you cut off you reuse in a stagger pattern again and restart every 4 boards layed

theres no point gluing the joists as soon as you lay the board and slot the board into the other board the glue has gone this one below not glued on the joists only the boards have been glued and screwed 3" away from the ends of the boards screw any closer any you cant slide your boards into each other

the screws also give you lines to follow when your screwing all the boards in after laying them all down so then becomes fast board screwing

 

[chrismac]

glue and stagger the boards dont go right up against the wall its better to use a 5mm spacing at wall sides

what you cut off you reuse in a stagger pattern again and restart every 4 boards layed

View attachment 523590View attachment 523591View attachment 523592

and your also in agreeance the boards joins (short side) dont need to land on a joist?

 

[Onoff]

Really only one thing to add to this, these:

https://www.screwfix.com/p/spax-tx-countersunk-self-drilling-flooring-screws-4-5mm-x-60mm-300-pack/88716

 

[gaz1]

note the 1st and second pic the edges are on a joist as the edges can fail if they are so far out fit some 2x1s as support for the board between the beams

or use any offcut of board and some 2x1s screwed to the beams as a bridging board if you cant be bothered making sure there on the beams

 

[harveyp6]

I didn't cut to make the short sides join over a joist because I thought all those joins were supported at both ends by the adjoining boards, and I haven't had any problems.

 

[gaz1]

I didn't cut to make the short sides join over a joist because I thought all those joins were supported at both ends by the adjoining boards, and I haven't had any problems.

have steps or someone jumping and those unsupported joints can fail as ive repaired many of them for that same example ive just said

 

[Welderpaul]

Really only one thing to add to this, these:

https://www.screwfix.com/p/spax-tx-countersunk-self-drilling-flooring-screws-4-5mm-x-60mm-300-pack/88716

I used these, pretty decent.

 

[chrismac]

note the 1st and second pic the edges are on a joist as the edges can fail if they are so far out fit some 2x1s as support for the board between the beams

or use any offcut of board and some 2x1s screwed to the beams as a bridging board if you cant be bothered making sure there on the beams

its not a case of not being bothered, 2x1 supports for what? I dont understand where they would go,

 

[harveyp6]

have steps or someone jumping and those unsupported joints can fail as ive repaired many of them for that same example ive just said

I won't be jumping about any time soon, but steps maybe, but although I didn't mention it, rather than flooring, it was loft boarding, which would get an easier life than flooring.

 

[Welderpaul]

someone jumping and those unsupported joints can fail as ive repaired many of them for that same example ive just said

What with 22mm board, glued joints with joists at 400mm centres? Not a chance in normal service.

 

[addjunkie]

What with 22mm board, glued joints with joists at 400mm centres? Not a chance in normal service.

Id glue the boards down too, stops any squeaky floors.

 

[gaz1]

its not a case of not being bothered, 2x1 supports for what? I dont understand where they would go,

2x1s across from each beam to beam used as support or 2x1s screwed to either side of the beam and a piece of board between the beams and screwed

What with 22mm board, glued joints with joists at 400mm centres? Not a chance in normal service.

when people are bone idol and jump off the steps and it does happen that joint can fail if not supported its the ladding of a person that starts to give at the joint and when it fails and it does, you can go through the board

chipboard is not like floor boards which are much stronger

 

[Pigeon_Droppings2]

chipboard is not like floor boards which are much stronger

Floorboards are less annoying too when you need access in future!

I'm not a fan of chipboard.

 

[Turbo]

I would not trust the t&g join to support itself unless it is on a light traffic area like a loft.

It's not difficult to screw an offcut of flooring on the short edge of a board to carry the adjoining piece. That way you have 22mm carrying the board, not the thin tongue.

I would not recommend glueing them either if there are any wires or pipes running under them. If you have to lift them for access it will be impossible.

 

[Agroshield]

After lots of reading up...

That is where you have gone wrong. Lots of reading up is not needed. One single piece of reading up, the installation guide from the manufacturer of the product you have bought, is all that is required.