laying hardboard under carpet

[Robbox]

Which is best nails for hardboard, looking at ring shank 20mm from Travis. They have a flat head, but I assume that will not show through any underlay and carpet.

The room is 4 x 4M, should I bother with the smaller sheets from B&Q and lay them staggered against the line of the floorboards or use the full sheets?

Also, what sort of nailing pattern is best?

 

[Doggit]

20mm nails won't go through the floorboards and hit any pipe/electrics so are perfect size; ring shank nails (unlike un-serrated) wont work themselves loose over time. Size of boards is down to you, and the quality of the floor; you are in essence trying to achieve a flat surface for the carpet, so an uneven floor needs large boards, but small boards can be more manageable - local woodyard will be cheaper than B&Q.
6 to 9 inch nail gap around the edge, with 9 to 12 in the centre. If the board flaps when you walk over it, then not enough nails, and no, they wont' show through. Get the best underlay that you can afford, and don't put felt carpet on underlay; chairs etc just sink straight through it.

 

[Robbox]

I saw a bag of serrated nails in travis today, I imagine 500g would be enough for this room.

The room is a bedroom, so no chairs, but traffic across certain areas.

It's an old house and the floor boards seem thinner and they are not T&G, so as you walk across the gaps the boards flex a little bit. I figured that hardboard would even that out and distribute the forces.

The fitter wants 170 for to lay hardboard! I figured...how hard can it be to do myself? So thanks for the advice.

 

[JohnD]

you can also use a hammer stapler and a big staple. Fast, cheap, and plenty strong enough.

I can't remember the staple size, it is a lot bigger than an office paper staple.

 

[Doggit]

A good woodyard should do the serrated nails as well as the boards. Travis is not cheap unless you've got an account, although they will haggle if you quote Wickes prices as they now own them.

I do use a stapler running from a compressor, but only with 20mm staples. A hammer stapler is good for breathable roofing membrane and paper prior to laying felt carpet, but it wouldn't get through hardboard and floorboards properly.

I think you've got the principles Rob, so go for it. Use a jigsaw for cutting the boards if you've got it, or a hand saw if you haven't. Lay the long side of the hardboard across the run of the floorboards, and then stagger them like bricks and you'll be fine.

 

[Robbox]

Thanks for the vote of confidence!

 

[footprints]

Just remember that if you ever need to raise a floorboard for pipes or alterations to cables serrated nails are a bitch to remove!
I have always used short hardboard pins or staples and never had the hard board come loose.

 

[lockjohn]

if you are laying hardboard it needs to be soaked overnight laid flat do not lay tight up to each other leave a good 3/16 gap at the joints otherwise it will ripple also lay smooth side down