Joinery Preservation

[chuggy]

I have some windows to make.

I am contemplating acquiring a couple of metres of 160mm underground pipe and fitting a fixed cap on one end and a screw-on cap on the other. Then I will insert the window components, cover with clear preservative (25l bulk-buy), screw on the cap and apply a low pressure via a Schroeder valve for 24 hours.

Any thoughts/ideas/suggestions, please.

 

[Racers]

Or you could vacuum out all the air and when you let off the vacuum the preservative will penetrate the wood.

Pete

 

[RobinBHM]

My thoughts,

-buy some Teknos 1410 preservative and dip your components, if using softwood.

-design your joinery with 2.5mm radius on all external edges.

-extend the 2.5mm radius through jounts of frames and sashes to create a V joint when assembled.

-make sure you dont have any water traps. Ie on dummy fixed sashes make 3 to 4mm smaller all round.

-use V joint sealer and end grain sealer, Teknos or similar.

-paint all surfaces before assembly.

-I would use Douglas fir, siberian larch rather than softwood.

If you really want to use softwood, use green split or engineered.

 

[chuggy]

Or you could vacuum out all the air and when you let off the vacuum the preservative will penetrate the wood.

Pete

Thanks for the suggestion. I am pretty well acquainted with the principles of vac-vac preservation but creating the vacuum on my proposed set-up is another time-consuming step.

 

[chuggy]

My thoughts,

-buy some Teknos 1410 preservative and dip your components, if using softwood.

-design your joinery with 2.5mm radius on all external edges.

-extend the 2.5mm radius through jounts of frames and sashes to create a V joint when assembled.

-make sure you dont have any water traps. Ie on dummy fixed sashes make 3 to 4mm smaller all round.

-use V joint sealer and end grain sealer, Teknos or similar.

-paint all surfaces before assembly.

-I would use Douglas fir, siberian larch rather than softwood.

If you really want to use softwood, use green split or engineered.

Thanks Robin. Some useful suggestions there. However, I haven't painted exterior joinery in 20 years. I much prefer stains. As for timber I don't have the luxury of buying profiles I need other than in Baltic Redwood and I certainly don't have the time to produce them myself from DF, Larch etc.

I was really looking for thoughts or ideas on my low-pressure treatment rather than merely dipping.

 

[YorkshireMartin]

I have some windows to make.

I am contemplating acquiring a couple of metres of 160mm underground pipe and fitting a fixed cap on one end and a screw-on cap on the other. Then I will insert the window components, cover with clear preservative (25l bulk-buy), screw on the cap and apply a low pressure via a Schroeder valve for 24 hours.

Any thoughts/ideas/suggestions, please.

For those of us that aren't familiar with this process, would you mind describing why it's done?

It's a form of pressure treatment, I understand that, but I didnt realise it was possible to do this on a smallish scale.

 

[RobinBHM]

I cant see that the pressure would be low enough to be any different to dipping.

You need to make the compnents, ready for assemhly and then treat. How will the preservative affect the glue jounts?

Also how will the preservative you use affect your stain finish?

In service, the tinber will expand and contract tangentially, so joints like the bottom rail of a sash will have the rail expanding against the stile. If you leave the joint flat and stain over, movement will crack the joint. If you radius each half of the joint the stain wont crack.

These are things you can do with standard profiles. Correct detailing for the surface treatment will have a greater impact on longevity than a diy pressure treatment.

 

[chuggy]

Unless the timber is already treated it seems we have a choice of applying preservative by brush/spray or dipping (and then use best construction techniques).

My idea is to try to use a relatively simple method to increase the efficacy of dipping.

If only time permitted I guess I should experiment with tests to find out relative preservative retention by dipping, pressure at 5 lb, pressure at 10 lb etc .

Only an idea guys; please don't get wound up about it

 

[Myfordman]

Make sure your adhesive will still bond well with the dipped timber.
No point is having a well preserved window that falls apart later!
I'd do a two test joints first, with and without preservative to be safe.

 

[MusicMan]

Using a vacuum to help impregnate wood is common in the musical instrument craft, especially of boxwood, maple etc (grenadilla is too impermeable). It is much better than dipping. We commonly use tung oil diluted 50/50 with thinner. Preservatives would also work well.

A PVC drain pipe is fine, best if it is clear then you can see the bubbles coming out of the wood when you switch on the vac pump. Cutting the wood open after treatment shows that it penetrates at least 5 mm.

A rotary high vacuum pump is best, with pressure tubing going to the pipe. I am intending to try it with a shop vac, and that may be enough to make some difference, but will not be so good.