Treatment for new cratch

[Tony Brooks]

One for the chippys.

 

I am building a new front board from Maranti (or that's what the timber merchant said it is) and need to treat it before fitting. I suppose traditionally I would varnish it but I really do not relish scraping it back to wood every few years so am wondering about some form of oil, maybe Teak oil to Danish oil.

 

Advice please.

 

 

 

 

[fudd]

http://www.wood-finishes-direct.com/brand/osmo

 

Try this link Tony. They have a few exterior finishes. Easy to apply. Top stuff

Steve

[Mike Jordan]

Light red or dark red Meranti is one of the budget hardwoods, regrettably its life expectancy is little better than you would get from a decent softwood. Having said that you can get reasonable results with varnish or oil based varnish both of which have strengths and weaknesses. Your suggestion of oil finishing would be ok providing that you do regular coatings and bear in mind that the dirt that falls on the timber will tend to stay there rather than washing off as with varnish. If you use Danish oil your will get a better result since this is really a mixture of oils with a varnish content which puts a surface film on the timber.

Exterior quality varnish or yacht varnish will give a good waterproof surface and is flexible enough to cope with the movement of the timber. It usually fails in time at the joints or other areas where water can penetrate or lie on the surface or in between the cratch board and the steelwork. Whichever system you choose, exterior woodwork needs regular checks and early maintenance.

If asked, I always advise oil based exterior varnish with the first coat thinned 50% with white spirit to soak in well and give a good key to following coats.

I tend not to trust the water based vanishes, although we are being forced towards their use by EU rules. Water based paints do seem to work well on cars though!

It helps if you follow good joinery practice and ensure that all exterior edges have a weather slope to shed rainwater (9 degrees is the recommended minimum) its also sensible to put the glazing beads on the inside rather than out in the weather!

If you want a timber that is extremely weather resistant then Iroko is the one to chose next time, it contains a natural oil which makes it last for years even if you neglect it totally.

I hope this missive hasn't depressed you, best of luck with the project.

Mike.

[Tony Brooks]

Thanks, looks as if it will be varnish then. I already planned to rout a radius on and horizontal exterior surfaces to help it shed water. I do not intend to use glazing beads because on the wooden hire boats they always seemed to be the cause of rot so I hope to bed the perspex on a small silicon bead and fix it by direct screwing. Hopefully that will make any damp visible and the screen easy to get out to clean and treat its recess.

 

The steel framed plywood one lasted about 7 years.

Edited November 24, 2013 by Tony Brooks