Why is this new external wood paint looking so bad already?

[MisterBoy]

We have a lot of old, traditional wooden sash windows. It had been quite a few years to my knowledge since they were last painted, with a lot of cracking and even some bare wood patches on sills.

About this time last year I hired a painter to repaint them all, he came recommended and seemed like he knew what he was doing but already there are some quite bad looking parts, cracks and discoloured or rough looking bits.

Can anyone tell what's caused this from my photos and what I can do? It seems the problem areas are all on the parts that were in the worst condition previously.

 

[DiyNutJob]

A good paint job takes more time than labour. I am not convinced painters you hire would ever get enough time for a good job. Unless you are willing to pay a painter to sit there and wait for the paint to dry, the job will probably fail in the time period you observed.

The big crack in the first pic looks to be failed caulking. Try a non-shrinking wood filler instead. If there's movement there then silicone sealant would work.

The second pic is probably to do with the sub-surface. Sand it back, clean it out, fill it in, prime it, and then overcoat it. You only need to repair the failed bits. Providing access is not a problem, painting is not hard to master or even hard work. In my painting DIY, I paint for 10 minutes and sit for 16 hours waiting for it to dry. I don't even need to clean the brushes. After painting, I put brush into jar with water or white spirit depending on paint type. When I need to paint again, the brush is ready to go. I use and reuse the same small plastic cup as a paint pot. I only put just enough paint in the cup for one cycle of painting. The leftover could stay in the cup to dry.

 

[MisterBoy]

Regarding the crack, that was pre-existing not part of the job - but the sill has gone a funny colour and obviously looks weird. From memory this was one of the places where the bare wood was showing through. I wondered if he'd been lazy in the preparation department.

I don't mind painting non-fiddly bits especially at ground level. I don't really know what I'm doing but have had good enough results though it takes me ages.

 

[DiyNutJob]

All cracks must be filled and then covered. If water gets in there, the wood will rot and paint will fail. The hired painter was likely rushed. So, some failures are inevitable.

Painting isn't hard. After a few goes, you will get the hang of it and speed up. Also, you will do a better job because you have the time, the pro's don't - they can't be quoting 1 week for a window, you'd just laugh even though it'd really take a week.

 

[MisterBoy]

Sadly I may have left it a bit late for painting this year, barring a warm week up in the north east. I'll have to get that crack filled though, I don't know why I haven't already.

 

[DiyNutJob]

It's not too late for water based primer/sealer. They dry fast and offer some protection. Oil based exterior paint is more difficult because of the rain. If dry weather, they only need 10C to cure, although might take longer than what the tin says.

 

[MisterBoy]

Is water-based as good? Although you mentioned primer specifically - are you maybe suggesting I get the primer done and wait until spring to apply the top-coat?

 

[DiyNutJob]

I find water based primer/sealer works as a top coat foundation (in contrast to oil based primer) and passed my test of time. Although I can't tell you if it's to do with the specific brand I used. Once dried in an hour or so, the primer is water resistant and so it offers protection for whatever is underneath. You don't need a full dry day for that to work.

For the top coat, you need oil based paint for longevity. Each top coat you apply would need a couple of dry days. This should be doable if there is a break in the rain.

Having something to stop water seeping in the cracks is better than nothing. Once the base is fixed, you can use the primer on it and wait for better times for the top coat.

 

[misterhelpful]

As has been alluded to, the time it takes to do the job properly is often too much work for some Decorators, or too expensive for some customers.
The dark patches on the ledge are likely caused by denatured wood (bare and grey looking), which may also have contained excess moisture when painted. This will cause the wood and colour to deteriorate further, while also allowing mould to grow below the paint surface. This makes the paint system fail and produces the cracking/crazing and discolouration you have.
It's vitally important to thoroughly clean and sand back denatured timber to a sound surface, or even replace it if necessary, in order to avoid the issue you have. Stopping further moisture ingress is also vital, so after sanding, repairing and priming, all joints should be caulked and then painted.
Oil-based paints have always traditionally been the best for exterior wood, but most of those are being phased out or are not as good as they were. There are some good water-based or hybrid alternatives available now but most are still not as good as the old oil based products. Unfortunately, I wouldn't count on many exterior products lasting more than 5 years, anymore, even on new and perfectly prepared timber.

 

[MisterBoy]

I was curious to see isolated cracks in paint that appears otherwise good... Perhaps movement of the underlying wood as there are different pieces and it's in direct sun?

Or maybe bad adhesion; though I didn't watch the painter work I'm suspicious that he didn't appear to do any prep other than washing the existing paint down.

 

[sparkwright]

I would say looking at the vertical bits he didn't do much sanding.

Is there shiny paint under the peeling areas?

Sanding seriously increases the life of paint, and avoids that annoying peeling which is so hard to rectify on the next re-paint.

Personally I would wait until next year now - nothing worse than an unfinished job for six months.

 

[opps]

It's not too late for water based primer/sealer. They dry fast and offer some protection. Oil based exterior paint is more difficult because of the rain. If dry weather, they only need 10C to cure, although might take longer than what the tin says.

Waterbased paints shouldn't be used if the temperature is going to drop below 10°c. Oil based paints can be used as low as 5°c.

Dulux Trade weathershield oil based undercoat is (light) shower proof after a couple of hours. The oil based gloss will end up with craters in the finish if it rains within 4(?) hours.

Another advantage of oil based finishes is that you can use Terebene to speed up the curing and Owatrol Oil to help the paint flow when it is particularly hot or cold. They also have greater longevity, from memory, DTW oil based has an 8 year life span, whereas the water based version is 6 years.

 

[opps]

I was curious to see isolated cracks in paint that appears otherwise good... Perhaps movement of the underlying wood as there are different pieces and it's in direct sun?

Or maybe bad adhesion; though I didn't watch the painter work I'm suspicious that he didn't appear to do any prep other than washing the existing paint down.

Exterior paints are designed to absorb and distribute UV sunlight.

Not sanding and providing a key is one of my many pet hates. A couple of years later, I turn up to paint woodwork. I start sanding and the paints just rips off the surface. It can result in increasing my prep time by up to 30%.

 

[opps]

Looking at the pictures, I am not convinced that undercoat was used. I could be wrong though.

Why not ask the decorator to explain why it has failed so quickly.

Is water-based as good? Although you mentioned primer specifically - are you maybe suggesting I get the primer done and wait until spring to apply the top-coat?

I am currently massively over running on the exterior of a double fronted, detached house. The sliding sash windows had been "restored/repaired" previously and left with waterbased primer over the bare timber. At the time of quoting, I was unaware that they had been like that for two years. I found 100 year old paint lifting where I would never expect to.

I'd recommend that you fill the sill crack with a MS polymer (eg CT1, sixaflex, etc). They are almost as flexible as silicone but they can be primed with waterbased paint and then coated with both waterbased and oil based paints. Silicone repels paint. If you have any exposed paints, coat them with an exterior primer and oil based undercoat and leave them until the spring (unless you are confident that you can finish them in a 2(?) week window).

 

[MisterBoy]

Is that the sikaflex EBT? I have a tube but it doesn't seem to advertise as being paintable. Although it's white and so is my paintwork...