Wood Glue

[Rick Hughes]

Need to have a high strength wood glue for a external joinery - joining some 8x2 beams end to end ... with stopped scarfed dowelled joints.

Originally was going to use my usual external adhesive (Resin W), but thought that a D4 adhesive with gap filling properties might be better.

AFAIK Polyurethane while having D4 waterproof rating are not that high in structural strength, especially when they have foamed to fill gaps.

The worst gaps are less than 1mm ... but want to use gap filling adhesive to prevent water ingress in future.

I could use an old style powdered urea-formaldehyde (used Cascamite previously not sure if Resintite is the same formulation) .. but this is D3 rated only .. just wondered if there is something better.

I see that there are 'Gell Polyuretane' such as Lumberjack:

Also glues with wood fibres such as Elmers Max:

Comments ?

FYI - if you are unaware D 'Durability' ratings come from BS EN304 .... and while may places advertise glue as 'Strength D4' or similar, this actually has nothing to do with strength ... and is water resistance rating:

D1 = Interior areas, where the temperature only occasionally exceeds

50°C for a short time and the moisture content of the wood is 15% maximum.

D2 = Interior areas, with occasional short term exposure to running or condensed water and/or to occasional high humidity, provided the moisture content of the wood does not exceed 18%.

D3 = Interior areas, with frequent short-term exposure to running or condensed water and/or heavy exposure to high humidity. Exterior areas not exposed to weather.

D4 = Interior areas with frequent long-term exposure to running or condensed water. Exterior areas exposed to weather.

[polygonum]

How about this?

EvoStik Polyurethane Wood Adhesive 310ml

Screwfix Product Code: 40778

Class D4.

IME it does not foam as much as other PU adhesives

[Rick Hughes]

Seems to be very similar to description for 'Lumberjack' i.e., 5min D4 Polyurethane

Interseting in all tests I can find Polyurethane comes off the worst for strength .. e.g.

[polygonum]

I don't really have anywhere that I have used this and been able to compare directly with other glues, but as a gut feel it seems significantly stronger than brown PU I have used. Trouble is, the woodwork has been rather crude so no two joints have been similar enough for a real comparison.

I know that such reviews are to be taken with huge quantities of salt, but many of the Screwfix reviews are quite positive.

[John Rumm]

If you want gap filling and strength, then you would probably need an epoxy like West Systems. As you say poly will fill gaps but not with any great strength.

[dom]

+1

[harryagain]

Unwise to rely on glue for any external/damp places joints in any critical application. Timber expansion/contraction soon causes failure.

[The Medway Handyman]

Boat builders might disagree.

[fred]

l+310ml/p78519

Resorcinol as used by boat builders.

I use Cascamite for out door applications. Find it excellent

[stuart noble]

Not likely to be much movement outdoors I wouldn't have thought. Moisture content in exterior joinery typically fluctuates between 15% and 17%

[Rick Hughes]

So would manufacturers of marine plywood & Glulam beams

However in this case this is to glue up Ridge Scarf joints which are also dowelled ... and bolted to 4x4 posts ... so not relying on glue alone

[Rick Hughes]

Cascamite, Polymite, Extramite etc. are only D3 rated and have to be protected from getting wet (paint etc)

Aerolite 306 is exceptional - but too expensive for just this job, as is Polyproof which is another superb 2 part glue

[Vir Campestris]

Not since last millennium. It's all epoxy now, although I admit to using a bit of PU on a small repair.

Andy

[harryagain]

Boat builders now use GRP exactly because plywood was no good. The only wooden boats that lasted (for a while) were traditional boats, traditionally built.

You see any glue in the Victory? How many Mirror dinghies are left?

And, how many Mosquito aircraft are left?

If you don't keep an outdoor flush door well painted, how long will it last?

Resorcinol as used by boat builders.

I use Cascamite for out door applications. Find it excellent.

Oh which ones?

[harryagain]

I know you don't park wooden aircraft outdoors. Not if you want them to last.

[fred]

I don't know where you are getting this from but I first used Cascamite to build a sailing dinghy 50 years ago. The boats was kept for 10 years. None of the glue joints failed.

7 years ago I made a wooden tripod to hold a sprinkler head for the vegetable garden. Cascamite is still holding it together. The wood is looking ropey as it was never stored inside but the joints are excellent.

Last year I built a wooden table for the patio and used Cascamite. I'll report back in 10 yeasr time.

[Bob Eager]

My father did a lot of small boats and canoes in his spare time and he used Cascamite a lot. Never had any problems.

[Tim Lamb]

In message , Bob Eager writes

I once used Cascamite 1 shot (53 years ago!) to glue a rather nice dovetail jointed Oak cabinet I made for a girlfriend's birthday present.

Lovely purple discolouration which had to be planed off:-(

[Rick Hughes]

On 11/09/2013 08:25, fred wrote:> On Tuesday, September 10, 2013

They are sold by manufacturer as D3 rated only ... that is where I am getting it from. Look at OP ...

D3 = Interior areas, with frequent short-term exposure to running or condensed water and/or heavy exposure to high humidity. Exterior areas not exposed to weather.

Which mean it is NOT suitable for immersion or constant water exposure unless protected by another finish (i.e paint)

Assume your dinghy had varnish or paint finish ? ....

If it could meet D4 Durability requirement then it would be sold as D4 ... it isn't.

[Rick Hughes]

I'm happy for him, but it is not the right glue for the job ... should be D4 rated.

Presumably successful as they had a finish over the glue, but they are not D4 rated.

Almost all wood boat building is now done with Epoxy which is fully D4 rated, and as gap filling as you want it to be.

I built several Beehives using Cascamite - all lasted fine, because white gloss paint kept water off the glue.