Screw sizes for loft boarding project

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I will soon be boarding my loft and need a bit of advice re screw sizes. I will be battening the loft with 175mm x 47mm battens and laying 18mm chipboard on top, what size screws would be recommended to screw the battens to the 3xisting ceiling joists and the chipboard to the battens?

Thank you.
 
Why are you laying the battens side on, they only need to be at 400mm centres and 50mm or so deep.

blup
 
I would have gone a little longer for the batten screws, one each side skewed in.
Why are you laying the battens side on, they only need to be at 400mm centres and 50mm or so deep.

blup
They need to be as deep as his insulation, presumably 170mm.
 
Are you screwing the battens alongside, and into, the existing joists or at right angles across them?

Is the flooring simply for storage or are you considering using the loft as a play/study area?
 
Are you screwing the battens alongside, and into, the existing joists or at right angles across them?

Is the flooring simply for storage or are you considering using the loft as a play/study area?
I am placing the new battens on top of the existing joists at a 90 degree angle and screwing down into the existing joist from the side. The finished platform is only for storage.
 
If the timber your are adding is going on top and you are screwing diagonally, I would recommend piloting the holes with a 5mm drill bit first. I'd say 70mm is a little less than ideal for this but you may get away with it. Make sure you alternate the screws on each side.

If I've not understood what you are doing correctly, if you are screwing through the whole width of the 47mm timber, I would recommend getting longer screws. 90mm would be ideal.

You can buy screws specifically for fixing down chipboard flooring, they are normally 45mm I think but the 40mm ones you have bought should be fine for what you are doing.

I'd recommend buying screws from Screwfix or toolstation if you buy any more as you'll find they are a fair bit cheaper
 
I dont think I am explaining this very well! Hopefully the attached pic helps. The diagonal lines are the screws. My thoughts are to screw diagonally into the batten and the joist.
 

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