External Strucural wood adhesive

[Osprey]

I need a very strong wood glue for external structural project. This is a number of vac-vac treated Glulam beans 270 x 90 and tanalized 150 x 150 posts. This will be made up of a number of posts joined with gallows brackets to beams.

The posts will have a 90 x 270 notch cut in the top so Glulam is resting for it's full thickness and depth - for some reason I can't think of name for the joint ..

This and the 45 degree struts that form the gallows brackets are trough bolted with 10mm thick steel Y plates ... on both sides - holds everything square. simple sketch on: (45 deg struts left out for clarity)

thought it worth putting a good glue on the Glulam to post joint, and the 45 strut faces.

Had thought about inserting dowels or biscuits - but been dissuaded.

Needs to be weatherproof glue, with moderate gap filling capabilities, no requirement for quick setting or initial grab .. quick googling around has told me that Phenol Formaldehyde, Urea Formaldehyde or resicornal glues would be best ...

And it seems a polyurethane glue is unsuitable ?

On previous jobs over the years I used Cascamite ... but guess better glues must now exist.

Welcome advice .. and some 'trade names' of what glue to look for.

[Leon]

Polyurethane can be strong and can fill gaps but does neither very well at the same time. I'd look for an epoxy or WeldWood.

[Chris Friesen]

From the picture it's sort of a modified half-lap joint, where only one member is actually cut.

If you glue the whole notch, any rigid glue will likely crack fairly soon due to cross-grain movement. If you're going to glue it, I'd suggest only gluing a few inches of the post above the notch.

Given the steel plates, I'd say glue is unnecessary.

Chris

[Lew Hodgett]

Laminating epoxy with a slow hardener and thickened with micro-balloons.

Anything else is down hill from there.

Check out Gougeon Bros for details.

Lew