Should I paint before fitting windows

[Jacob]

Having done a fair amount of re-painting over the past couple or three years, the main reason exterior wood rots out is due to lack of maintenance and poor initial preparation. Poor design is also a factor. I'm not convinced that linseed oil paint is substantially better than modern paint, but I wouldn't be surprised if it was.

I'm convinced - I've been using both for 50 years and the superior performance of linseed is beyond doubt for me. I now don't use anything else (externally) - I've seen too many failures of modern paints.
Strictly speaking modern linseed oil paints are 'modern' but have very much in common with the old paints - except for having no lead (and some other toxic substances). They can be touched up after a few years with just more linseed oil.
The big difference in a nut shell is that modern paints are very durable in themselves but don't always stick to the wood - water gets in behind and the paint lifts off - the flakes still in good condition as they fall to the floor and the woodwork rots! Hence the need for preservatives.
But linseed oil weathers and deteriorates from the surface, not from behind - so it looks dull but stays firmly stuck for years , until the last traces are washed off. No lifting, flakes or cracks, so can be touched up or covered again with oil alone or paint, at any time, after a bit of a wash down if necessary

 

[RobinBHM]

But linseed oil weathers and deteriorates from the surface, not from behind - so it looks dull but stays firmly stuck for years , until the last traces are washed off. No lifting, flakes or cracks, so can be touched up or covered again with oil alone or paint, at any time, after a bit of a wash down if necessary

virtually all joinery manufacturers use water bourne microporous paints now. They dont harden like the traditional alkyd based gloss paints. These water based products dont suffer oxidisation which hardens alkyd based products, they stay soft. Weathering causes the surface of the paint to erode, so the film thickness gradually reduces -in line with comments above about linseed paints

The key to minimise re-decoration cycles is to design the joinery to allow water shedding, avoid water trapping and capillary action issues as well as avoiding sharp corners.

Whilst Im sure linseed paint is a great product, it isnt practical for a joinery manufacturer to use it.

Modern paints arent carp, but to achieve extended time between decoration cycles requires all the elements to work together; good joinery design, correct application of end grain sealer, correct painting techniques to achieve optimum coating thickness, correct storage and treatment on site and correct fitting ensuring all end grain cuts are properly sealed etc.

Usually when problems with paint peeling or other faults appear it is automatic to blame the paint, when in fact its often a combination of faults leading to paint cracking and peeling.

 

[ED65]

Usually when problems with paint peeling or other faults appear it is automatic to blame the paint, when in fact its often a combination of faults leading to paint cracking and peeling.

Ditto with glue. Almost everyone blames the glue when there's a failure and often they look for a 'better' replacement (as seen in threads here and every other woodworking forum I read) when most of the time it's down to a problem with materials or a failure in method.

 

[Jacob]

Usually when problems with paint peeling or other faults appear it is automatic to blame the paint, when in fact its often a combination of faults leading to paint cracking and peeling.

Ditto with glue. Almost everyone blames the glue when there's a failure and often they look for a 'better' replacement (as seen in threads here and every other woodworking forum I read) when most of the time it's down to a problem with materials or a failure in method.

If I follow the instructions on the can and other sources, use well known branded supposedly good quality materials, and it still peels, then I blame the paint. I've seen it happen too often in too many different circumstances.
Actually it's glaringly obvious - thorough application of timber preservative is more or less standard nowadays. This means one thing; the paint is no good on its own.

 

[Jacob]

...

Whilst Im sure linseed paint is a great product, it isnt practical for a joinery manufacturer to use it.....

Why not?

 

[garethharvey]

...

Whilst Im sure linseed paint is a great product, it isnt practical for a joinery manufacturer to use it.....

Why not?

Probably due to the time it takes to dry.

 

[RobinBHM]

If I follow the instructions on the can and other sources, use well known branded supposedly good quality materials, and it still peels, then I blame the paint. I've seen it happen too often in too many different circumstances.
Actually it's glaringly obvious - thorough application of timber preservative is more or less standard nowadays. This means one thing; the paint is no good on its own.

Im making a comparison with professional supply exterior paint made for joinery and its application for joinery. We have excellent technical back up from our paint supplier and notes on how to detail joinery and fitting.

If paint fails at joints, mitred glazing beads, mitred cills, sharp edges or where timber parts are butted together for example where a trim may be cut to a cill then they are all areas where incorrect detailing has caused the coating to fail, not a fault of the paint itself.

A typical example is where paint cracks at the junction between the bottom rail of a door and the stile. The rail is wide so a significant movement occurs and the paint cracks at the joint line, eventually moisture gets in, wicks along the rail end grain and paint starts peeling.

Linseed paint couldnt be used for joinery manufacture, too slow to dry, not suitable for spraying, probably too soft for delivery and installation.

 

[Jacob]

......
A typical example is where paint cracks at the junction between the bottom rail of a door and the stile. The rail is wide so a significant movement occurs and the paint cracks at the joint line, eventually moisture gets in, wicks along the rail end grain and paint starts peeling.

Not if it's linseed. It doesn't peel and it floods cracks, keeping moisture out.

Linseed paint couldnt be used for joinery manufacture, too slow to dry, not suitable for spraying, probably too soft for delivery and installation.

Yes you might have to change your work routines! Is too soft for delivery and installation and has to be painted in situ, though can be primed in the shop.

 

[Phil Pascoe]

Surely priming defeats the object?

 

[garethharvey]

Surely priming defeats the object?

Not all woods require a primer with this paint, the primer however, is raw linseed oil.

 

[Jacob]

Surely priming defeats the object?

Not all woods require a primer with this paint, the primer however, is raw linseed oil.

Yes primed with oil. Best if warm and in a warm workshop. Very easy to apply, very easy to clean, no VOCs, no solvents required, nothing toxic.

 

[ED65]

Usually when problems with paint peeling or other faults appear it is automatic to blame the paint, when in fact its often a combination of faults leading to paint cracking and peeling.

Ditto with glue. Almost everyone blames the glue when there's a failure and often they look for a 'better' replacement (as seen in threads here and every other woodworking forum I read) when most of the time it's down to a problem with materials or a failure in method.

If I follow the instructions on the can and other sources, use well known branded supposedly good quality materials, and it still peels, then I blame the paint.

That's fair enough within reason. But you're tarring modern paints with a very wide brush here. All other things aside no matter how many windows you've personally painted that's a very small sample group. We don't know if 75% of other users of the same paints had much better experiences (for a host of reasons we can only speculate about).

You're going by what you've seen with your own eyes which is fair enough. But I can give a counterexample that I've seen with my own eyes from the family home. It is only a single case but it shows that modern paints aren't all cr*p (your exact words) and don't always crack or flake or peel, even after zero maintenance for ~20 years. Instead the paint weathered down in just the way that you described linseed paints do a few posts above, while I can guarantee that that isn't what was used.

Actually it's glaringly obvious - thorough application of timber preservative is more or less standard nowadays. This means one thing; the paint is no good on its own.

That's one interpretation. Another is they're taking a belt-and-braces approach based on known failure modes of wooden windows.

The thing is this knowledge base goes way back because since at least the 70s DIY books have been advising to use preservative or sealer on end grain where possible and the implication of this can't be over-emphasised in this context: the rotted windows they were basing the advice on would go back to a time when linseed oil paints were still common, if not ubiquitous.

 

[Jacob]

.......

Actually it's glaringly obvious - thorough application of timber preservative is more or less standard nowadays. This means one thing; the paint is no good on its own.

That's one interpretation. Another is they're taking a belt-and-braces approach based on known failure modes of wooden windows. .....

I'd amend this to; "known failure modes of wooden windows painted with modern paints"
Preservatives only started being used routinely fairly recently, from the 70s as you say. Old joinery seems to survive very well without it - unless totally neglected for a very long time, or until stripped and painted with modern paint, which is the kiss of death!

 

[ED65]

By definition those were old windows painted with old paints, so I reject that amendment

 

[RossJarvis]

I think the main problem is with the painting not the product. Modern paints are very good and in many respects much better than linseed oil paints, particularly in regard to finish and colours, but nobody wants to put the effort into proper maintenance.

Even with older paints, including linseed oil, there came a time to strip back to bare wood, you can't just keep on painting on top of paint, at some time there'd be more paint than wood. This used to be between 10-15 years. So prime properly, undercoat and top coat. every three years rub down and re-coat. after 10-20 years strip back to bare wood and start again. At the very best today you could expect to re-coat after 8 years.

What really happens? The joinery turns up and even if the joiner has said what the primer is and paint regime should be, the painter slaps on whatever he has in the van., if lucky the process is controlled and a correct system is followed. In my experience, more than often, one top coat is applied. When it comes to repainting, people select someone on price and go for the cheapest, which is someone who may wipe down with a rag and then slap on a single coat of whatever the client wants. On a job I did a couple of years ago the painter was recommended on how quick he worked, particularly as he did no prep.

I've never known paint to flake or peel if done properly, only if something has gone wrong (not always obvious to the user). Two main problems are painting over badly prepared/deteriorated paints, or using a non compatible paint system over something else. Unfortunately the data sheets given by manufacturers don't really cover all the essentials.

The days have now gone where people realised you need to strip back to the wood regularly, so I'm fairly sure the days of long lasting woodwork have gone. That's why I recommend plastic joinery over wood, I don't like it but it'll last longer with neglect than wood will.

 

[Jacob]

....
Even with older paints, including linseed oil, there came a time to strip back to bare wood, you can't just keep on painting on top of paint, at some time there'd be more paint than wood. This used to be between 10-15 years. So prime properly, undercoat and top coat. every three years rub down and re-coat. after 10-20 years strip back to bare wood and start again. At the very best today you could expect to re-coat after 8 years.

Not sure if this is true. I started enthusiastically stripping my grandparents joinery many years ago. A victorian house in Nottingham. It rapidly became obvious that it had never been stripped before and I was removing the accumulation of 100 years of paint - which was in fact in excellent condition but just a bit thick around the mouldings etc. It was also extremely difficult to do (3 bay sash windows, half a ton of lead paint etc) and obviously pointless.
I think paint work was cleaned down and touched up with very thin coats (linseed oil paints don't work if too thick) and never stripped back. Hence the longevity - once stripped and repainted the life of the woodwork would be drastically reduced.
Since then I've worked on hundreds of bits of old joinery and basically never encountered the tell tale signs of stripping - burn marks on the wood.It was never done.

.....
I've never known paint to flake or peel if done properly, only if something has gone wrong (not always obvious to the user).

That's what is called a 'truism'. The question is - have you known paint to flake or peel (I certainly have) when paint does peel is it the fault of the paint or the painter? I've learned to blame the paint.

PS about incompatibility - they don't recommend it but I've found that linseed oil sticks brilliantly to other defective paints - and also seems to stabilise it - floods into cracks and soaks into bare wood. So no need to strip back - just brush off loose stuff and sand back to a nice edge. It may not work with all paints of course.

 

[garethharvey]

My house was build in 1904, we have quite a decorative bit of woodwork just under the 2nd floor. I stripped this back to the bare wood in 2015, this was the first time it had ever been stripped back. There was minimal pain on there. I would estimate this had been painted once every 20 odd years.

The quality of the wood is as good as it was when it was put in place 113 years ago. I would argue that this would would not have survived 113 years with modern paints.