issues with laying oak floorboards on to joists

[guymad]

Need some advise. I am building a games room in what was a garage and need to raise the floor by 100mm + floor boards. I want to use 18mm solid oak floor board with T&G on all 4 sides and secret nail to the joists with king span insulation in the 100mm space between the joists. Questions are :
1) the board lengths are random in length as T&G is it ok not to have a joist under the joint where 2 boards but together?
2) with kingspan in place between the joists how can I use board clamps?

 

[WoodYouLike]

as long as the battens are no further apart than 35 - 40cm and every floorboard connects with at least 3 battens you're alright

Why would you use clamps? You're secret nailing the boards, aren't you?

 

[ladylola]

As said you probably won't need the clamps but if you do feel the need to anyway just use the old carpenters method of folding wedges.
Cut a section of your board into a wedge shape, with the groove still on. This will sit against the flooring. next screw the other side of the ripped piece down to the top of the joists and tap the piece with the groove thus clamping your flooring.
It'll be time consuming as you may (well will) have to repeat for every board.

 

[guymad]

as long as the battens are no further apart than 35 - 40cm and every floorboard connects with at least 3 battens you're alright

Why would you use clamps? You're secret nailing the boards, aren't you?

I thought you need clamps to pull the joints in tight and then nail?

 

[WoodYouLike]

You run the risk of over stretching when you do this (causing the board to lift)
The force of the nailer will help to keep everything tight, plus of course the higher quality of boards you purchase the better the T&G will fit anyway.

 

[ladylola]

Nothing to do with the original question really but a quick story about floor clamps.
I was working on a floor once with another couple of carpenters one of whom was wearing the bib and brace type of overalls. He was kneeling down and cramped the boards and popped in a couple of nails. He then come to stand up only to find the material of his overalls had become caught between two boards When we stopped laughing we did release him of course , and he was a tad more observant after that

 

[Symptoms]

mad - if you really do need to nudge the odd board over then use the old screwdriver (or chisel) trick:

At the offending position drive the tip of a screwdriver into the side of the joist (maybe 50mm below the joist top) and use the length of the screwdriver as a lever to ease the f/bd over and into position for nailing. This is a great and quick method which can be employed 'on the fly' and saves time. However, I doubt you'll ever need to use it as most boards available these days tend to be 'straight' and easy to fit together. I've got a couple of Record f/b clamps (had 'em for 30+ years) and only have to get them out when fitting very, very wide reclaimed boards.

The floor nailer (as others have said) will drive 99% of boards into the correct position for nailing under the action of the activating mallet/hammer.

 

[ladylola]

Ah yes the old screwdriver trick I always recall at college we were told that it was " the subbies rough way of doing it" . It may be rough in some eyes but I've done it and I'd bet every other chippy in the world has done it at some time.
The only thing I'd add to using this method is to use a small grooved offcut between the board tongue and the screwdriver to prevent damaging the board.

 

[stevethejoiner]

I am assuming the garage has a DPM and heated.
And yes, cramp the boards, but I would not secret nail.
You cant get joints up tight enough with a screwdriver or a lever to counteract any moisture shrinkage if the garage is heated.
If you don't get them up as tight as possible you will get shrinkage gaps later.
With a traditional cramping method secret nailing is not an option, but if your using solid wood, what is wrong with visible fixings? You may as well fit engineered wood if you want a modern look.

If you cramp, you cramp in blocks not individual board runs.
Firmly fix board no1 against a wall and place at least four or five more board runs on the battens, cramp the last board run with several cramps along the full length of board (sacrificial timber is required between cramp and board).
You will know when the boards are tight as board run no3 will lift/bow up off of the battens, as you apply a little more cramp pressure boards 2 and 4 will start to rise, do not over cramp now as the boards spring up and will break the T&G.
Walk onto your boards and check that your body weight pushes the boarding back down onto the battens, you may have to bend at the knees and put some spring into it. If not release cramp pressure.
It is a compromise between getting as much lift in the boards as you can without them breaking open but not too much that you can't get them down flat again, as the smaller the space you allow for the boards to fit into the tighter the joints will be.
Now firmly fix down the cramping board no5 and then 2,3 and 4.
You could pilot drill and and skew nail with floor brads, the oak will cause the brads to go black, but this could be an aesthetically pleasing feature, alternatively counter-bore, screw and plug with off cut oak board.

You asked how do you use cramps with infill insulation?
By cramping 5 rows of boards you can leave out the insulation where the cramps are. When first rows of boards are fixed remove the cramps and replace insulation and so on.

"Tip" buy or hire a moisture meter and make sure the wood is around 7- 9% before you fix them down.