Treating exterior oak

[Jelly]

If you're really committed to having a coating, you could try using multiple coats of something like kreidezeit base oil, which is used for mixing linseed oil paints and varnishes, and will form a genuine coating, which is (somewhat) capable of accomodating the natural movement of wood (any other genuine linseed oil based "stand oil" would do).

However without pigments and resins you'd need a lot of coats to build up a sufficient film thickness to prevent the wood becoming exposed and weathering, and with it being a relatively soft coating, whilst it will self-heal a little bit when scratched, it would almost certainly perform poorly with the significant abrasion I would imagine a table top recieving.

Probably still more trouble than it's worth, but it's an option which will provide an actual coating, whilst remaining sympathetic to the natural appearance, and accommodates the natural expansion and contraction of wood (alkyd varnishes and resin based coatings generally don't like wood movement, and will begin to crack and flake quickly, requring complete refinishing frequently to avoid weathering occuring in a less than attractive patchy fashion).

 

[Cabinetman]

Hi, i’ve just been back to your original question which we seem to have gone away from, so, slabs of oak, outdoors but undercover, some areas with copper or stainless studs? to stand hot pans on.
I can’t see anything wrong with copper or stainless, or brass for that matter, I have used the last two with oak and not had a problem. Personally I would treat the oak with an exterior yacht type varnish and have some marine polyester covers made to cover them up when not in use. Think elasticated corners. Ian

 

[Steve_Scott]

I’ve never seen it done with oak but it might be worth considering treating the worktop like a canoe and costing it with a marine epoxy to seal it and then a varnish to give some UV protection to the epoxy. It’s not maintenance free but might be worth a look?

Another solution, thinking outside of the box, is to not use oak to make outdoor worktops... there’s plenty of options that are far more stable and durable.

 

[JAW911]

Only use stainless steel for your studs/rods for pots and pans. Copper whilst looking nice will stain the oak. Oak (like douglas fir, sweet chesnut, etc) is so reactive with metals that you really can only use SS. In Bury St Edmunds you are not near the sea so you won't need 316 quality - A2 or 304 grade will suffice. I used Osmo exterior UV oil on an oak bench and the finish on the flat panels lasted less than a year. I even used their 'primer' and that had no benefit. Better to leave it natural in my opinion.

 

[Nautilus21]

You appear to want to keep asking the question until you get an answer you like.

Oak exposed to rain and sun goes dull in a year and grey in 2 years. Max.

not really - otherwise I'd have happily used Osmo like 'the bloke in the shop' said - I came on here to get other opinions and explore options - hopefully with real experts who know - hence asking questions....

I haven't used many oils/finishes in the past outdoors so want to make sure I've explored all... and thanks for your input..

 

[Nautilus21]

I’ve never seen it done with oak but it might be worth considering treating the worktop like a canoe and costing it with a marine epoxy to seal it and then a varnish to give some UV protection to the epoxy. It’s not maintenance free but might be worth a look?

Another solution, thinking outside of the box, is to not use oak to make outdoor worktops... there’s plenty of options that are far more stable and durable.

thanks Steve.. already got the oak slabs unfortunately - otherwise would not be using oak for this project!

 

[Nautilus21]

I use oak a lot. Most of my buildings are made out of it and clad in it. I use offcuts to make thick chopping boards etc for my outdoor kitchen.

Do not apply a finish. You will regret it. During the year you get heat, frost, hot sun and soaking wet rain. The wood will move. It is very durable though. The finish will look terrible inside a year and it will become a trial renewing it. A jetwash every year is what I do.

Thanks for this...

why do you need to jet wash out of interest?

thanks

 

[Austin Branson]

Thanks for this...

why do you need to jet wash out of interest?

thanks

I think you’ll find that jet washing will clean off a lot of the dirt, and it’s the dirt that’s black, not the oak. I agree with most of the answers you’ve had on this, and definitely agree with the advice to leave it untreated.
I think you may have problems with it moving. I don’t know how long it’s been since your timber was felled, but if it’s less than about 10 years it will move. You can attach galvanized steel fabrications to stop it moving successfully, but there is no way you’ll bring it back once it has moved.

 

[Claud1]

I used a product a few years ago called Flexterior and it has lasted well but it is not available any longer but I suspect any high quality Yacht varnish may be as good as anything

 

[AJB Temple]

Yacht varnish will not protect exterior oak in a horizontal exposed position unless it is reapplied frequently. Having had some yacht experience, with a teak decked boat left natural, and mahogany varnished to high gloss elsewhere on exterior cabin joinery, you will be dealing with discolouration and flaking regularly. But salt spray is harsh.

The jet washing I suggested, strips off all dirt, green mould and the greyness and takes the oak back to a natural colour. Some people do this with buildings, and also use oxalic acid. It works but again is a job to do.

I jet wash our garden furniture every year. It restores it cosmetically but does raise the grain and is not ideal for joints.

 

[Bm101]

Seem to remember Custard did a properish test comparing Osmo and Sikkens external. Sikkens was slightly better on external oak but there were disclaimers. Unless you want to continually (annually) maintain then leave it as bare oak. Part of the charm for me is the weathering.

For a bbq area I'd be tempted to leave oak bare. However this is not 'advice'. Be warned.
Give it a good scrub up with green pads in the spring or jet wash it. Let it dry, quick sand then maybe oil it with an oil like rapeseed etc and continue to maintain like that during the summer months of UK bbq use.
I'd use copper bolts/studs because they are softer than your pots. Also look nice. I wouldn't be worried about staining personally from domed copper nuts etc if used seasonally.

What I'd really make sure of was that I could remove the slabs and store them internally during the winter in a garage or shed.

 

[Nautilus21]

Seem to remember Custard did a properish test comparing Osmo and Sikkens external. Sikkens was slightly better on external oak but there were disclaimers. Unless you want to continually (annually) maintain then leave it as bare oak. Part of the charm for me is the weathering.

For a bbq area I'd be tempted to leave oak bare. However this is not 'advice'. Be warned.
Give it a good scrub up with green pads in the spring or jet wash it. Let it dry, quick sand then maybe oil it with an oil like rapeseed etc and continue to maintain like that during the summer months of UK bbq use.
I'd use copper bolts/studs because they are softer than your pots. Also look nice. I wouldn't be worried about staining personally from domed copper nuts etc if used seasonally.

What I'd really make sure of was that I could remove the slabs and store them internally during the winter in a garage or shed.

Great advice thx.... hadn’t even thought about taking them off for the winter..... lots of the rest of the area is also made from oak (shed cladding, sleepers etc) and some of that has been treated with OSMO before I started this thread!! I’m really happy to do maintenance every 3/6 months as required.... sanding/oiling wood etc i don’t see as a chore digging weeds etc is another matter!

 

[Nautilus21]

Yacht varnish will not protect exterior oak in a horizontal exposed position unless it is reapplied frequently. Having had some yacht experience, with a teak decked boat left natural, and mahogany varnished to high gloss elsewhere on exterior cabin joinery, you will be dealing with discolouration and flaking regularly. But salt spray is harsh.

The jet washing I suggested, strips off all dirt, green mould and the greyness and takes the oak back to a natural colour. Some people do this with buildings, and also use oxalic acid. It works but again is a job to do.

I jet wash our garden furniture every year. It restores it cosmetically but does raise the grain and is not ideal for joints.

Makes sense thanks

 

[AndyT]

A couple of earlier discussions in this area:

My own experience with Le Tonkinois varnish on an oak garden chair. I take it indoors in winter and have refreshed the finish. It's lasting nicely.

https://www.ukworkshop.co.uk/threads/found-a-good-finish-for-outdoor-oak.107328/
RogerM's really useful long term experiments with Sadolins and Sikkens and other finishes

https://www.ukworkshop.co.uk/thread...olin-classic-vs-sikkens-filter-7-plus.108601/

 

[Cabinetman]

The reason I suggested yacht varnish as a possibility was that in the original question this piece of oak is going to be undercover, I also suggested fitting an elasticated cornered bag over it, in this situation I can see no reason why it wouldn’t work. Ian