Outdoor wood preserver and finishing product?

efunc

Hi all,

I'm new to all this but coming to the final stages on a floating bench project. The seat is comprised of a couple of new scaffold boards made of an untreated rough sawn white softwood. I'll be sanding them down, but not too much. The bench is located under a canopy roof, so it will not be rained on, however will be subject to seasonal humidity changes and temperature etc.



I've never made anything like this so need to know what products to apply to finish the wood. My goal is to protect the boards from twisting and bending and stabalise them as much as possible. I don't want to colour it too much really. A slightly golden colour or light oak is fine, and it adjoins a cedar clad garden room. I also don't want a glossy or plasticy look. I like the idea or an oil or wax, but I'm not sure if they do much in terms of long term protection. One thing I do have in my shed is some Barrettine Clear Universal Wood Preserver which I bought for the garden room:

• Contains Tebuconazole, Permethrin & IPBC.
• Protects uncontaminated timber against wet rot, decay and wood boring insect attack.
• Suitable for use on all types of timber, rough, sawn or smooth.

Barrettine

I've also come accross a similar product, OSMO WR Base Coat, which actually sounds similar, but more suitable:

1. Extremely water repellent
2. Resistant to blue stain, rot and insect attack
3. Reduces wood swelling and shrinkage
4. No future application necessary
5. 4001: Oil-based, brush or roller applied only

WR Base Coat

Both of these are just a base product requiring the use of an oil or other finishing product. The OSMO specifically mentions that it "Reduces wood swelling and shrinkage" which appeals to me, but is this also implicit of other similar products, like the Barrettine Clear Universal Wood Preserver? If not, I may choose to buy the Osmo WR Base coat instead.

Does anyone have experiance of either? And what of recommendations for a low sheen product to go over the top for a bit of depth and protection? Osmo oil, Tung oil, Boiled Linseed?

Thanks for any advice

danrv

The Barretine would be ok. Solvent based and probably wouldn't need reapplying again for a long time.
I've used Cuprinol clear wood preserver with good results. It gives a slight golden tint to light wood. Water based, easy to apply and soaks into the wood well.
May need reapplying a couple of times a year depending on exposure to the elements.
Maybe consider covers also to protect the wood from bowing. 

efunc

Thank you. There are differences between these two primers though which might be important, but I don't really know. The first is that Osmo say their's reduces wood swelling and shrinkage, but The Barretine doesn't. I don't really know if it does or doesn't though, and it seems fairly desireable! The second this is that teh Osmo one says you only ever need to apply it once, and it's permanent, whereas the other one should be reapplied after a few years, which seems crazy if it's to cut ends and inaccessible wood joints and under a coat of oil or wax.

danrv

Any wood preserver would do the job.
Not too cheap though. 
Solvent/oil based would naturally be water repellent and longer lasting. Osmo also do UV resistant versions.
You could treat the inaccessible cut ends with varnish or something durable before assembly.

efunc

Thanks, it's the desire to prevent excessive bending, cupping, twisting that I'm trying to acheive before finishing with a topcoat. The bench will be undercover, so I'm not expecting direct sunlight or standing water.
I'll contact Barretine to see if this product possesses those qualities and if not will try the Osmo. I may well be finishing with Osmo decking oil anyway.

efunc

I went ahead and ordered Osmo WR Base Coat which is quite expensive,  ut I'll see how that performs. I'll be leaving expansion gaps betweek all the joints too. And when it comes to screwing down the boards, I've learned that less is better and that I should drill slotted holes to allow the wood to expand and shrik  whilst being screwed down.

twopenny

Twisting and bending will be down to having seasoned wood and the support the planks have if you've done it correctly.
No ,preserver will make up for that.

efunc

The support for the boards is very good, completely solid all round with no flex. The boards themselves though are rubbish. Standard 'A1' scaffold boards, but basically soft white sap wood which will probably behave like a sponge. But I'm going to sand them quite finely and seal them and they'll also remain under a covered area and in the shade so not open to the elements. Time will tell..

bjorn_toby_wilde

You’ve done a nice job of putting that together. You’re right about scaffold boards though and looking at the pictures those will probably crown to some extent. Sealing the end grain will help as it should slow the process.

Maybe leave the finishing for a little while though until they’ve finished acclimatising? You can always plane or belt sand them once they’ve settled down.

I’ve just had to lift some floorboards in my son’s 1901 terraced house. Perfectly flat timber because it was quarter sawn and properly seasoned. Not like the kiln dried rubbish we have to put up with today. 

efunc

Thanks for that, I'm fairly pleased, given that I haven't really attempted anything like this before and in my head it was a quick 2-3 day knock-up job. In the end it became more like 2-3 months, and also many ££££ in materials! But it's solid with about 30 chemical anchors securing every point to a firm fixing and utilising interlocking and half-lap joints wherever possible to distribute load and allow for movement.

You're right about old timber. I would never throw out salvaged wood if at all possible. Stuff we have from 1920 through to about 1980 seems so much denser than the fast grown rubbish today. Old fence posts can sit in wet ground for decades without even a trace of decay seemingly because it was slow grown heartwood. Such a mistake when I recently replaced some with newer stuff. Doh!