Lengthening Timber

[Argonaut]

I have a large outside framing project .. Pergola and then tied into roof over a large deck area.

I posted a Q on scarf jointing .... https://www.ukworkshop.co.uk/forums/scarf-jointng-t61618.html

To go with this ... what is currently the best external waterproof glue.


Timbers will be pressure treated softwood ...not the best material for glue ... but all joints would expose clean wood ...for glue surface.

In past I have used Gorilla Glue but recent test reviews have rated this the weakest .... so my usual Evostick Resin W Waterproof PVA glue would be my next choice unless someone knows better.

I have used Cascamite on large lay up projects, but it is a pain to keep having to mix small quantities when doing a joint at a time.

 

[mrpercysnodgrass]

You could try this http://www.agwoodcare.co.uk/prod/polyur ... _grab.html

 

[Eric The Viking]

You could try this http://www.agwoodcare.co.uk/prod/polyur ... _grab.html

Bookmarked, thanks!

E.

 

[Argonaut]

The test report I read shows PU glues are the weakest of all glues.
They are fast grab and Gap filling, but low strength.

 

[Eric The Viking]

The test report I read shows PU glues are the weakest of all glues.
They are fast grab and Gap filling, but low strength.

That's odd. I've a strong suspicion PU is used in laminated beams. If it's weak, it's an odd choice.

 

[Steve Maskery]

I've had great results and disappointing results with PU outside.
The best outdoor glue I've found is West System Epoxy.
S

 

[Argonaut]

The test report I read shows PU glues are the weakest of all glues.
They are fast grab and Gap filling, but low strength.

That's odd. I've a strong suspicion PU is used in laminated beams. If it's weak, it's an odd choice.

Maybe in manufactured beams with perfect face to face fit and machine pressure it is good ... in home made joints it seems not ...

I can't upload any files to this site (upload never completes) so can't attach report ... but here is a link to it...

http://www.finewoodworking.com/Materials/MaterialsPDF.aspx?id=28897

 

[Mike.S]

The best outdoor glue I've found is West System Epoxy.

+1

A bit pricey, but I've used it for repairing window cills - gluing in new timber and 'filling' gaps/cracks and impressed with its performance.

 

[andersonec]

Ask yourself this, If I buy some expensive formula for this job, am I going to use all of it or have half left over to go to waste?

For a couple of minutes mixing some Cascamite which very strong, waterproof, cost effective, no waste, very long shelf life, it will all get used eventually on various other jobs.

To me it's a no brainer, think about it and you should come to the conclusion it's not really a pain to mix up a little Cascamite as and when you need it.

Andy

 

[Argonaut]

I was (and suppose still am ) a fan of Cascamite, my 'thought' here would be I was using Cascamite 40 yrs ago.

There have been such inroads in adhesives, would have expected there was something that now surpassed Cascamite ...

 

[Phil Pascoe]

I was (and suppose still am ) a fan of Cascamite, my 'thought' here would be I was using Cascamite 40 yrs ago.

There have been such inroads in adhesives, would have expected there was something that now surpassed Cascamite ...

............or that cascamite now is different to what it was then, maybe?

 

[Harbo]

A. Sq

 

[Argonaut]

A. Sq

?

 

[custard]

Another vote for Cascamite. I've been using it for boating projects for decades and always found it a reliable and reasonably priced product.

Incidentally, a few years ago Fine Woodworking ran an exhaustive series of tests on various glues, the final conclusion was that there was only the tiniest differences in terms of absolute strength, the cheapest yellow glue performing virtually the same (or even better on some timbers) as the most expensive glue (West Epoxy).

There were however three major conclusions. Weather resistance varies hugely, so for an outdoor (or even a bathroom/kitchen) project pick the glue with care. The quality of the joinery work swamps the choice of glue in determining strength. End grain gluing has almost zero strength, and a 45 degree mitre isn't half way between end grain and long grain, it's actually a lot closer to being end grain.

 

[woodbloke]

I've had great results and disappointing results with PU outside.
The best outdoor glue I've found is West System Epoxy.
S

That's an excellent, if spendy choice for a marine application where the timber is immersed constantly as in boats. Try Everbuild D4 which is also waterproof and ought to be available for around £5 a litre...I pay a little less that that. Good stuff :wink: - Rob

 

[Argonaut]

Interesting Rebuild data sheet states that D4 although fully waterproof is not suitable for Load Bearing application


Quote " • Not suitable for load bearing applications, use Everbuild 502 Wood Adhesive."

and 502 is a D3 adhesive, and not suitable for this job as external wood will be subject to full exposure.

As for Cascamite - it has changed names a few times as company changed hands ... Extramite, Polymite ... but back on sale as Cascamite. (current owner seems to be Polyvine)
This is also only a D3 rated adhesive ... not fully waterproof.

 

[johnf]

My choice would be Aerolite 306 they built spitfires with this ( I think ) 100 % waterproof and stronger than the wood itself

 

[Argonaut]

My choice would be Aerolite 306 they built spitfires with this ( I think ) 100 % waterproof and stronger than the wood itself

Aerolite 306 was originally developed for the deHavilland Mosquito bomber, don't know about the Spitfire.

 

[johnf]

My choice would be Aerolite 306 they built spitfires with this ( I think ) 100 % waterproof and stronger than the wood itself

Aerolite 306 was originally developed for the deHavilland Mosquito bomber, don't know about the Spitfire.

Well Mosquito or Spitfire it must be good its easy to use I have built boats with it never had a disaster yet

 

[Argonaut]

I have used this in past when I had to build four 5' high bass 'horns' for a powerful club sound system ... built up the curve by using this to glue 1" x 1" strip to follow former.

Although when I had next 'contract' I swapped to Cascamite as to me it seems it had better gap filling properties, it was a sod to sand down though.