Is this a proper flooring screw?

[redhexagonal]

My hallway is screwed down randomly with these screws. They are 50mm , do they look like they are the right ones to secure 22mm chipboard? I noticed a few have come loose and spin in their holes

 

[John D v2.0]

50 is too short, you would need more like 70 x5mm for that situation, especially on existing joists with lots of holes in already

 

[Deleted member 174758]

They look like a suitable type of screw - flooring screws should either have an unthreaded shoulder (like those) or have a small length of opposite-direction (left hand) thread at the top. Normally onto new joists 2x floor thickness is regarded as being adequate (we normally go for 4.0 x 50mm with 18 to 22mm flooring), but that is with new joists. The length that manky old joist need may well be greater, as John says, however, be very careful to ensure that you aren't going to screw the floor down with longer screws only to hit a wire, conduit or pipe going through the joists (always worth checking first by lifting a board or two). Sometimes a thicker screw (e.g. a 5.0 x 50mm screw) is a safer approach.

 

[foxhole]

I always use fully threaded screws, smooth section at the top means the board is only held down by the head, chipboard is not dense enough for that meaning the board can slide on the screw resulting in loose boards , as you have found.Should also be glued .

 

[Deleted member 174758]

I always use fully threaded screws, smooth section at the top means the board is only held down by the head, chipboard is not dense enough for that meaning the board can slide on the screw resulting in loose boards , as you have found.Should also be glued .

I agree with you on the glue - boards should always be glued, however, if you glue the boards down and use the proper screws at the correct centres that's good enough in my experience. In point of fact collated flooring screws are only ever of the plain top of shank type.

Technically, when you pilot for screws the hole through the upper piece if timber is supposed to be a clearance hole, so the thread shouldn't be able to gain any purchase on it. If the thread goes all the way to the head you always increase the risk that the board will "jack off" the joist below, leaving a gap between the board and the joist.

Personally I find life is too short for piloting sub-flooring - I just stand with my feet either side off the screwing point and drive in. My collated gun does 4000 rpm the impact driver does 3600 rpm. Both pull up tight every time (well, almost)

 

[big-all]

its also worth noting the safe zone for electrics not in line or expected areas like vertically or horizontally between fixings like switches and sockets is 50mm below the surface including on floors
now on a floor there are no electrical fixings and you always check for services but on say a wall your 50mm screws are the limit iff things are within the safe zone to be certain