When painting outside woodwork with undercoat and gloss I usually go over the areas that are heavily exposed to rain and sun with a second coat of gloss. But i've never actually read anywhere that this will prolong the life of the paintwork. Am I wasting my time?
The bond between the wood and the first coat of whatever is on there has to be good. The rest is really just decoration
Why do something if you do not know why you are doing it?
It seemed like a good idea at the time.
Rednadnerb,
Paint specification from an AKZO rep on external paintwork (preparation and priming assumed to be done) for longevity:
2 undercoat and 1 gloss coatsOR
1 undercoat and 2 gloss coatsBut always remember that it's the preparation that gives the longevity on any paintwork - if that is poorly done, then the finished coats will simply not last.
Cash
Well, it gives your paintwork an extra thickness, so that would help it survive _external_ factors. Just so long as the underlying adhesion between the wood and the paint is sound, so it doesn't flake off then it sounds like a reasonable idea. After all, we know from expereince that the perparation takes longer than the painting, so if an extra coat extends the lifetime of the work by prportionally longer than a strip / prepare / repaint would, then it's a worthwhile investment in paint and time.
If you are painting new wood or over very weathered old paint, consider "Ranch Paint", which is microporous.
I used it on well weathered paint several times (having removed the flaky bits and rubbed it down). Worked a treat and didn't "peel". From past experience, ordinary undercoat and gloss would have.
Ranch paint isn't cheap but you don't need an undercoat and the finish is good- albeit satin rather than gloss.
Probably not good over good old paint as you'd have to do some serious sanding.
Brian
I strongly disagree.
After a lot of experience in painting wood, I came to the conclusion that what painting does, is pretty specialised, and goes like this.
1/. Knotting. This stabilises the wood and prevents resin creeping under the paint.2/. Filling removes major imperfections.
3/. Priming mainly has to stick to the wood, and provide a key for other coats.4/. Filler primer gets rid of grain and other minor imperfections
5/. undercoat is there to provide the base colour and reflective coating.6/. Top coat is there to fine tune the colour, and to provide a tough surface to protect what is below. On cars, you often see that as a clear lacquer, with the normal paint actually being the 'undercoat'.
Now in an outdoor situation, if the top coat gets compromised the underlying coats will fail. Typically UV attack splits the top coat, and water gets into the wood dwells it and splits the paint off.
IF - and its not certain - a second coat of top will retard UV attack, or maybe a coat of UV resistant lacquer will stop it getting to the gloss, its well worth putting ion.
One of the fundemental principles of exterior painting is to repaint before the original starts to crack thus maintaining the protection.
If you go to the trouble of sanding back to bare wood, wood hardener is the thing to use. After that, any paint goes on like a dream and tends to stay there
.. use something other than wood. ;-)
Don't get me wrong, wood is fine outdoors for trees and bonfires but I would love to get rid of it's use here outdoors asap.
30+ years ago I moved here and put up a new paneled fence. The second set of panels are showing their age whilst the concrete posts look as good as the day I planted them. Rather than replacing the 6" square gate posts for the third time I have a pair of steel ones in the garden ready to go in. The uPVC windows haven't had a lick of paint (or much attention of any kind for that mater) in the 15 or so years they have been in. I just wish I'd made the picket fence out of solid plastic board or steel rather than wood when I replaced that a few years back.I wish I'd had plastic soffits when we had the extension and windows done back then. One less thing to have to waste time, effort and money on (knowing it will all have to be done again a few years later).
Wood does have it's purpose though ... it makes nice furniture. ;-)
Cheers, T i m
better to do one of primer, 2 undercoats (the build) and one top
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.