Exterior clear coat for rural timber house

We have a 1980's timber kit home on a farm block that has a lot of clear coated window frames and doors. While many of these are on the veranda away from direct sunlight and rain, many are fully exposed to the elements and cop a fair bit of sun and rain. Not surprisingly there's a lot of weathering of the existing clearcoat breaking down to expose the raw timber.

This is a long house with lots of windows so I'm looking for a compromise between a very robust clear coat and one that doesn't cost the earth. So wondering if anyone has recommendation/experience of a good weather resistant and UV resistant clear coat and what is the recommended number of coats etc? I might need to use two different products, one more expensive for the exposed timbers and a cheaper one for the ones under the veranda. Also, do I use different product for the raw timber prime coat and/or the final top coat for example? Any feedback and experiences of longevity would be good.

Gday Russell

Maybe some close-up pics of the surfaces to be painted might help.
cheers
Keith

There is NO known clear product that in those circumstances will will withstand UV for more than a year before it starts to deteriorate. Your choices are ; sand and re-coat every couple of years, let it go grey, or use an opaque paint. I sanded and clear recoated 3 times a set of 9 casement windows before I gave up and opaque painted them 15 years on and they still look OK.

What Bob said - paint is your friend.

Before we built we wanted natural timber framed windows, but speaking to a neighbour soon put us off that. He was totally fed up with the constant maintenance, having tried any number of different clearcoat products. Suffice to say we went with an industrial grade powder coat on metal frames - I have enough other painting to do on the house without having to do windows too !!

For what it's worth, the best I've found in terms of longevity for outdoor timber is the Sikkens Cetol system, but this isn't a clearcoat (see comments above). This job wasn't windows, rather a large solid timber outdoor sign I had to put together for a client (constant exposure to sun and rain). A single large flat surface beats fiddly window frames any day. Boards were glued together using polyurethane glue (AV 515) which was a bit of an experiment in itself, but is holding together perfectly 5 years later.

A long-lasting finish with Cetol products needs 3 coats (!). One of Cetol HCSe in the tint of your choice (the teak looks OK), followed by 2 coats of their Filter 7 UV protection product (clear). 3 coats is an awful lot of fiddly work for windows.....rather you than me :rolleyes:. The end result still looks great, but will probably need a sand back and recoat soon after 5 years outdoors.

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I agree about options there - just wondering if there had been any recent improvements. The first and second images were FeastWatson years ago, so didn't stand up well. First one easterly facing and cops morning sun and direct rain. Second is exposed but southerly aspect. Last is original clear coat on verandah that is about 30 years old so due for renewal.

Definitely no recent improvements in anything Feast Watson related; in fact, most of their products have gone seriously backwards in recent years IMHO. Other forumites may be able to suggest the "best of a bad bunch" from other manufacturers. I've found Sikkens to be one of the few who are still serious about professional/trade products. I used some Bondall Marine Grade clear finish recently, but it hasn't been outside long enough to tell if it's any good or not.

Thanks. I was thinking of using Sikkens for the worst exposed bits. I agree 3 coats is needed in these conditions, but not FeastWatson, I'll try something else. I see there are also boat varnishes but probably expensive.

Whilst some commercial products may perform better than others the main fact is even when carefully applied a clear coat over a wooden substrate is a very difficult technical ask. Mostly coatings fail due the the degradation of the timber substrate beneath the coating resulting in cracking and flaking in the horizontal areas especially where sharp edges have lower film build. Whilst coatings with high levels of UV absorbers help best results are obtained by coatings that have some pigments making the clear semi-transparent. Australian exposure conditions are some of the worlds toughest and getting coatings to work on a variety of Australian hardwoods even in pigmented form also causes issues. I recently also saw some severe paint failures after two years exposure on weatherboards that I suspect was due the the failure of the European imported factory applied primer flaking off the substrate along with the topcoats. (the primer did not have the flexibility to withstand the extremes of movement ) In regard to clears for both decking and windows one school of thought suggests that modified oil based in either solvent or water based forms is the easiest option but again with some colour pigmentation. This type of technology slowly erodes away by oxidation in the weather rather than flaking off and hence is just a matter of constant recoating rather than a full stripdown to maintain.
Cheers,
Paintman

Thanks everyone for the info. It's going to be a choice between Sikkens and Intergrain products (DWD) as they both have a primer coat and a tinted top coat. i'll use a paint stripper to remove the current varnish to ensure the best bond, then at least top 3 coats, so it'll be a bit of a job, but that's the only way forward it seems. Most of these products are designed for decking or outdoor furniture that are completely exposed to the elements.

My rear house extension is cedar weather boards exposed on the north side and sheltered by a roofed pegola on the east side (back of house). East side is mostly windows and a set of French doors - all cedar.

I used the Sikkens system as outlined above. The north side needs to be treated about every 8-10 years. It’s a wash down with a stiff broom and soapy water then recoated with the Filter 7.
When I put the pegola up, the rear was pretty bad (it had been fully exposed and neglected) so it was all windows out , everything sanded back then a coat of Cetol HSE? then two coats of Filter 7. That was over 10 years ago and it still looks great.

I know it’s a different situation but I used Intergrain on my front veranda timber floor - I’m not impressed.