Gluing treated wood

[Chris Hogg]

Is it possible to glue wood surface-treated with mangers creocote, using evostick polyurethane wood adhesive? I shall nail and screw the join as well, but would I just be wasting glue?

[newshound]

Good question. Given that it doesn't actually "varnish over" the fine surface features (like polyurethane would) you should still get some of the mechanical keying. On the other hand, since it renders the surface hydrophobic I'm sure it would reduce the effectiveness of PVA type adhesives (where, presumably, surface tension helps to draw the particles of emulsion into the surface). I guess polyurethane adhesive

*will* wet the relatively oily surface left by creosote, but the creosote will presumably fill some of the porosity that would otherwise help the adhesive to "key".

Even if it does not provide much tensile strength to the joint, its gap filling qualities will provide some shear strength but I'm sure you are right to add some nails or screws.

[Paul]

There's some advice here, just not for treated lumber.

And the conditions of the test are pretty ideal. It's a furniture wood test.

Paul

[polygonum_on_google]

I am not in the least surprised by polyurethane doing so poorly.

It can be useful but it isn't strong. (I use it for wall plugs into crumbly walls and oversized/misshapen holes. Make the hole and dampen it. Coat and fill the plug with PU. Let it set. Cut off any excess that has foamed out. Then screw into the plug.)

Shame they didn't include any of the softwoods. Quite possibly their differences are so great that the bonds might have been very different.

And they didn't test Aerolite or similar.