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Best Paint System for Sash Windows

Hi all, I renovate, draft-proof, repair, and paint sash windows. Ive been using Sandex Flexi gloss of late, also occasionallly used Sikkens Satura, and Little Green Oil Eggshell.

I went fully oil based externally when we set up our own buisness, I wanted to move away from the sub contracting days of flying on quick dry undercoats and then oil gloss on top. I do miss the finishing times but feel ive been offering a much better finish.

Since joining up on another forum and doing more research, some Acrylic systems seem to now be getting reccomeded over Alkyd paints, more flexible, less pealing/ flaking, also water permiable.

For example the Zinsser Allcoat sounds fantastic. Also has some antifungle agent, Zinsser says can be used on the inside of the windows aswell, and has some adhesion resin similar to 123 so will adhere to glass.

Where is TP at the moment are you swithing to wb on sash windows? One main advantage i can still see for oil/ Akyld is sashes have moving parts so should withstand rubbing and knocks from use more than the more flexible Acrylic paint.

Be greatfull to hear your thoughts ? Stik to oil or go to w/b?

My currant customer isnt too conserned anout sheen finish just doesnt want pealing or craking and good durrability.

Hi Chris

There isn’t a right and wrong answer to the best. However there are different degrees of QD primer and waterbased systems, and also culture differences seem to figure in choice of water based over oil and microporous over non-microporous.

In 2011 I did the “Mythic house” all acrylic over old oil. It was in semi gloss sheen, which is the same sheen as most high gloss looks after a year of weathering IMO. It was very easy to work with and fast drying was a huge advantage, especially in rain-soaked Britain.

When speccing the front doors, I would have said that oil based onol primer and a Sikkens oil topcoat was as good as it got, which for finish is still the likely case, but something changed in 2010 and their oil undercoat/primer dry times went through the roof, and I found the system almost unusable. The savings on drying times of the quicker drying water based Sikkens Onol primer were significant. It stuck to well prepared old oil gloss and there seemed to be no noticeable sheen difference in the oil based topcoats.

It is interesting how Zinsser has become the go-to Quick Drying primer shop, nothing wrong with that, as the products are strong, but if something goes wrong, you have no comeback from any other brand company if the top coats don’t perform.

If you use a full Zinsser spec,that negates that potential issue, so you are likely on to something looking at the Allcoat system! But be aware that waterbased All Coat is a copy of a Classidur product and I had this from a dec last March who didn’t like the copy.

The worst covering paint we have ever used( white by the way). Nice & smooth to use quick drying, but thats it! Some areas took 5 coats to cover, & this is white over white.

Zinsser QD coverstain isn’t too shabby as a primer/undercoat. I do hear of issues on to glass. I believe oil based gloss still offers a very high adhesion properties on glass, so keep Coverstain off glass and finish with the tops onto the glass.

@pd67 should have some good info to confirm how the waterborne Valtti specs perform on Shetland. And it is a good idea to ask Holmans who rate Repair Care and Valtti exterior paints, saying it is a whole different ball game compared to the repair system with conventional dec trade paint.

Culturally, in Holland, it is oil all the way outside, they use Sigma and Sikkens a lot.

As far as oil based and microporous, Northern Europe seems really into it. However (and @BenSturges may need to confirm I have my Scandinavian trivia the right way round), I believe in Sweden they wouldn’t dream of using a microporous oil based system, preferring to lock the surface down for 10-15 years with the standard Swedish oil paint system.

That’s me all exteriored out :slight_smile:

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I can confirm that the Valtti system is excellent.
On Windows and doors if previously painted in oil I would go with oil based Otex primer and top coat x2 with Unica Akva.
Developed to go over smooth wood it is a great drop of paint with a satin finish. It dries hard and looks good. You have to be quick with it though!

Hi Chris,

I’ve never been sure about sash windows, whether I should remove or paint in situ.
Most bay windows I’ve painted only have one sash that opens, so it’s never been a big deal as long as that one works smoothly. I think it would give a better finish to remove them, and smoother movements but haven’t been brave enough to try.
What would you recommend or do if you don’t mind me asking?

@andycrichton, Thanks for your reply Andy, I was hoping to get your well rounded opinion on this one.

You make a good point regarding the Allcoat system, it is a complete system as Zinsser recommend.

It seems to be coming down to oil, which should be solid, resist knocks better (sashes moving in box, hitting cill etc), but potentially have joint/ movement cracks in most weathered areas after 2/3 years which need touching up. Or Acrylic which could potentailly resist cracking for longer but less knock resistant and wears away/ picks up dirt easier.

I haven’t tried the AZ Gloss only the HD many years ago, its interested Sikkens now ok the quick dry primer for spot priming, this should atleast help getting all spot priming and frame sealing/ putty work done in the same day. The last Sikkens I used on sashes was the oil based Satura inside and out, i was really impressed with the solid finish.

Re Coverstain, the oil/ solvent based quick dry coverstain adhesion on glass has allways seemed pretty solid and very tough to remove, I do agree tho a fully cured oil offers the best adhesion to glass.

@pd67 Thanks for the feedback, I was speaking to Holmans last week, the recommend finish for exterior gloss windows was a full coat of Otex primer, followed by two coats of the Valtti Ultra. She did recommended overlapping/ sealing the glass with the Otex primer and then applying the ultra on top of the Otex as Ultra wont adhere to the glass as well. How did you find the flow and speed of application of the Otex compared to the Zinsser yellow tin Coverstain?

Hi @Willis_Decorating , removing the sashes is far superior to painting them in imo, even if another company has done the draughtproof service to a ground floor easily accessible window I would still prefer to take it apart to paint. You can get to all of the box and stiles to remove the ridged build up of paint that can effect the operation. You can also temporarily put the windows in over night after each coat but making sure you have air gaps around the sashes and frame so each component can dry effectivly. Its extra work, but works well when you’ve got the order of process figured out. Its also nice to wax around the top of the frame and the sides of the stiles before reassembling, gives you a nicely restored smooth operating window. The bare minimum your likely to need is new sash cords, new parting beads, and some weights to balance the windows.

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Hello Chris,

Firstly I have to tell you that I usually come on here looking for advice not giving it! But last year I wanted to try something different for some exterior work and I tried some Zinsser AllCoat (satin). It went on really easily,was a bit shinier than Superdec (super satin) and went on really easy. Looked nice when dry and customer preferred it to the Superdec. Wouldn’t stick to the glass though and coverage was terrible - my heart sank when I put the first coat on! This was the only time I’ve used it and I’m still learning to decorate so my experience is limited compared to everyone else on here. I just wanted to join in really!


Hi Chris, I can buy Otex and Coverstain locally. In my opinion Otex all the way for ease of use, can be tinted, coverage and finish for sanding etc.