Which glue?

Whilst my loft plans state to attach 6"x1" to my existing 4"x2" rafters.
My BCO said he would be happy with 2"x2" glued and screwed to the existing 4"x2".

Just wondered what everyones adhesive of choice would be for this?
Gripfill?
Pva wood glue?
Epoxy resin?

PVA or PU, possibly UF (urea formaldehyde glue, e.g. Cascamite, etc). GripFill won't hack it

Cheers Job,

Any particular brands to look out for?
Naturally, I'm looking for affordability + performance.

Shame about the gripfill (ease of application/cheap)

If it where me, I would ask him!

Epoxy is very good, and the only one on that list that can structually gap-fill, it also doesnt not require a clamping force for a good bond and is fully waterproof, unlike PVA. But I would say the final bond very much depends how clean the old joists are, and its also a sod as you have to mix the two parts, well, in fairly small batches.

Ive not done it, but I would say the best option in terms of balancing easy/effectivness is polyurethane (PU) , bascally the same stuff sprayfoam is made from, only just in a tube/bottle which you apply, its then foams lightly on the job, bonding where there is contact, and foaming to fill the void semi-structually where the is not. I dont think any one brand is any better than another really. But your after PU wood adheasive, not the sikaflex/tigerseal type adheasive/sealent in guns

I dont know how feasable it is, access, and presents of nails etc, but if its filthy there may be millage in running a power plane over the tops of the old joists to get something to get a good bond to. Your aiming to stop it sliding, at all, so you get the stiffness of a 6*2 instead of a 4*2 and a 2*2 ontop of each.
- 6*6 = 32
- 4*4 + 2*2 = 20


Daniel

Just for clarity, its my rafters. Not the joists. If that makes a difference.
At the moment I'm just trying to work out the cost difference.

A) Nail 6"x1" to existing rafters

26 lengths of 6"x1" is going to cost £160. + The cost of the nails.

B) Glue and screw 2"x2" to underside of existing 4"x2"

26 lengths of 2"x2" is going to cost £73. + The cost of the screws and adhesive.

Could well be the 6x1 works out cheaper/easier in the long run.

As Daniel says, you're after the wood adhesive (sold as Gorilla brand amongst others, but many other firms do the stuff much, much cheaper). I'd not really considered epoxy - I've rarely come across it (West System - the one made for boat building -being the main one to date) probably because it is damnably expensive. By PVA I should have said D3-type (i.e. cross-linked, exterior grade, etc - who'd use anything else for joinery) which should be adequate as the area it is being used in isn't fully exposed

As it's a cold day, again, today, maybe a reminder about temperatures and glue is in order. NON of these glues sets well at low temperatures. Possibly only epoxy will set at just above freezing point - the rest require a temperature or 5 degrees Centigrade or so to get full strength. And if using epoxy, PU or UF glues disposable gloves are an absolute must