Sistering joists - nail or bolt?

[shutter_speed]

Hi all,

New build garage, 35x86mm joists at 570mm intervals. They have a span of just over 6m. I intend to board the centre section for storage of lightweight items. The joists are in two pieces, joined by nail plates, and I want to reinforce this section. I intend to use a similar piece of timber (though I can't find 35x86mm so will use 38x89mm studwork). Question is:

How much should I overlap the current joist by? I was just thinking 600mm each side of the join - so sister with a 1.2m length? This is purely because I then get two pieces out of each 2.4m length of timber I buy.

Should I glue and bolt (I was thinking 3 x M10 coach bolts each side of the join with large square washers both ends), or glue and nail - just bang a load of 18 gauge nails through with a nail gun?

Thanks!

Edited by shutter_speed on Saturday 12th December 10:26

[bobtail4x4]

do you mean the bottom chord of a truss?

or are the timbers really small?

[Aluminati]

600 would be fine, as long as you are not going to store half a dozen engines up there.

M10’s at 150 centres with washers as you mentioned.

[shutter_speed]

bobtail4x4 said:

do you mean the bottom chord of a truss?

or are the timbers really small?

Yes, bottom chord of a truss. Aluminati, thank you, sounds good.

[Flibble]

Wouldn't 18g nails be a bit thin for this? That's a tiny little finishing brad.

[J6542]

For all a few extra lengths of cls will cost you then I would just leave them at 2.4 and overlap 1200 and coachbolt them. To be honest in my own house I would just fire in a load of 5.0x 60mm screws as long as nothing really heavy was being put up there.

[bearman68]

J6542 said:

For all a few extra lengths of cls will cost you then I would just leave them at 2.4 and overlap 1200 and coachbolt them. To be honest in my own house I would just fire in a load of 5.0x 60mm screws as long as nothing really heavy was being put up there.

This, plus this.

https://www.screwfix.com/p/evo-stik-polyurethane-w...