PVA and pressure-treated timber

[Elessar]

While waiting for a glue-up to dry (a beehive stand - hi Mary!) I passed some time by actually reading the instructions on the Unibond Exterior Wood Glue bottle. I was surprised to find it said "do not use on pressure-treated timber". Does anyone know why?

It's certainly cured OK and has survived the last three weeks of sun and rain. And I've certainly glued pressure-treated wood with exterior PVA (can't be sure what brand though, or whether it said the same in the small print) on other things that have survived in the garden for years.

Polyurethane glue is probably an alternative but I'm not sure it expands biscuits as a water-based PVA does.

[Andy Hall]

I'm not certain about the issue with pressure treated timber if any, other that perhaps the treatment reduces the ability of the glue to bond.

Regarding PU glue,..... You can use it with biscuits. WHat I tend to do is to apply the PU glue to the slots and surfaces on one component and brush to form an even layer, then I moisten the other surface and biscuit and assemble. This has proved effective.

The normal rules with PU glue apply:

- Make sure that the surfaces are a good fit. It is not a gap filler.

- Clamp well while curing

- Don't get it on your fingers unless you want it there for a week.

For other wood glues, I tend to prefer the Titebond aliphatic range (traditional and Titebond II) which are aliphatics.

.andy

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