Modern metric floorboards are just a little thinner than the old fashioned imperial ones - about 2 mm.

Is there a simple dodge to build up the joist, or have I really got to plane a wooden shim for each ruddy joist - about 64 at the last count?!   I have seen Marley floor tiles used in the past but don't want to go down that route as they can split when nailed.

Thanks,

JohnD

Adding to what big all said a timber yard can machine boards to match the existing ones and still be cheaper than the DIY sheds.

a quick dodge, use 2mm window spacers

Result!  100 foot of floorboard, good quality, planed to exact size.  Cost  was £60 for 100'.   Cheaper than thinner stuff from B & Q.

It would have cost more for a tongue and groove, but I didn't want one, as the joists are every 18" so springing isn't going to be much of a problem with a 5" x 3/4" board, and absence of the groove will make it much easier to get the boards up for the next rewire.  

Thanks, Dewy!

JohnD

John IMHO you would be better off getting it t&g'ed it's not just there for support, although that is its primary purpose. But as the boards contract and expand it helps to fill the gaps, which otherwise howling gales can blow through; bringing masses of dust with it.

And wait till someone drops something and it goes rolling along the floor and drops through the gap

John I have written this as much for someone else who looks at this thread and would otherwise get the impression that it is good practice, which it isn't.

Keith