Should I nail, and glue my hardwood flooring?

Question

Well since I'm waiting for an answer on my first hardwood floor question I might as well throw my second question out there too.

I’m face nailing my new hardwood flooring (Tasmanian Blackwood 19mm x 130mm) then puttying the knot holes and nail holes. This will be done through the whole house. The subfloor is Particle Board (Brand name: Yellow Tongue) that has been glued and screwed down.

Additional information: This is solid T&G timber flooring that was purchased direct from the saw miller. In the event nailing and gluing is recommended, there would be no moisture barrier.

My question:

Is there a benefit to ‘nail and gluing’ my hardwood flooring to the Particle Board subfloor or will this just interfere with the natural expansion and contraction of the hardwood?

Answer 1

You said the subfloor is particle board, so if there's some kind of isolation under that you don't need more barriers.

Attaching your floor to the subfloor depends on what kind of floor that is. If it's floating floor, it needs to float, so no gluing at all, and you need some kind of padding to level out the floor. Generally floating floors are tongue/groove or click install.

And if it's kind of parquet you have to glue it to the subfloor, because the grip of nails to particle board is very weak.

Answer 2

At 130 mm (5 inch), you're at the edge of the range for a nail only installation. Certainly most hardwood manufacturers recommend gluing for widths greater than this.

You may be able to get away without gluing, but if you're in a high moisture area, the floor boards may cup. Gluing would help mitigate this. Talk to the the manufacturer's rep for the appropriate installation in your area.

What I don't understand is why you would be face nailing the floor. T&G is typically installed using a special floor nailer which puts the nails in at an angle through the tongue, such that the nail is hidden in the groove of the next board. You should only need to face nail the final one or two courses of boards, where the nailer won't fit in against the wall. The savings in labour over face nailing and filling the holes is tremendous. In my experience, hardwood is HARD. Face nailing often requires drilling first, so the nail will actually penetrate the wood without bending.

Rent an air compressor and a floor nailer. With it, you will be able to do about 300 sq ft. a day (25 sq m). Without it, you'll be able to do half that or less.

Answer 3

Think of it this way - what other methods could you use? You have to somehow get the floor firmly attached to the subfloor, otherwise the seams between the planks will be loose and water gets in there and the floor is ruined in no time. So at least you have to glue it down and once you've done that nailing it will not make any real difference.

I've seen a lot of hardwood floors that have been glued down, usually to concrete, and they serve just fine for dozens of years under reasonable humidity. However I once saw hardwood exposed to water for a long time - it expanded so much that planks were torn off the concrete base and I'm sure that no nails would prevent that. That part needed serious repair.

Nailing hardwood floors is almost always useless, because if the glue is intact it will hold the planks but if it fails then nails won't help - stepping onto different parts of a plank that it not perfectly glued will make the plank bend slightly and pull the nails out and it gets loose over a course of month. If you want some metal fastening - at least use wood screws, they won't be pulled out.