Linseed putty or 2 part wood filler for sash window refurb?

I’ve had a few quotes for painting my sash windows that will require some of the window putty redoing in areas where it is loose and falling out.

Half the decorators suggested using 2 part wood filler (same as used for car bodywork). The advantage of this is they can paint it within an hour or so. Just concerned whether the lack of flexibility is an issue.

The other half wanted to use traditional linseed putty. On paper this sounds better, but it should really be left 3-4 weeks to harden before painting, however I guess this is a bit impractical for pro decorators who want to get in and out quickly so one suggested he would prime it within an hour and the other said he’d give it the weekend to skin over.

Wondering what is the lesser of the 2 evils. Non traditional car filler or linseed putty that hasn’t hardened fully before painting.

The two part will trap moisture and cause rot around it

I’d go for putty. You would need to leave it for quite a while to skin. The puttying should be quick and easy. It’ll be two trips but it will be done properly. I’m restoring some windows at the moment and the hardest parts are definitely where they have been bodged in the past.

I’ve renovated a few sash windows now. The two part epoxy filler is rock hard, the differential expansion has caused cracks almost everywhere I used it. I won’t use it again.

The other half wanted to use traditional linseed putty. On paper this sounds better, but it should really be left 3-4 weeks to harden before painting, however I guess this is a bit impractical for pro decorators who want to get in and out quickly so one suggested he would prime it within an hour and the other said he’d give it the weekend to skin over.

Do it properly. The ‘pro decorators’ just want to get and finish the job, take their money and move onto the next job, and have no concern for what your windows will look like in time. Use proper putty, as it helps absorb shocks which could shatter the glass, as it never fully hardens (well, it takes a very, very long time, and you’ll be removing old stuff and replacing it when you next paint your windows anyway). I’m currently restoring a Victorian front door, with leaded glass panels, and I’m doing it properly, because it’s my home, and I want it to look as good as possible, for as long as possible.

Get some better decorators in.

Toute pret single part wood filler, I used it for patching sash windows, very impressed.

No the “pro decorators” will go for putty and charge accordingly for time and visits taken. Few pro clients willing to pay though. Look out for starlings if you have lots roosting locally they’ll come and eat the putty for you.

Epoxy will not expand or contract so will crack. In 2yrs time you’ll wish you had used putty.

Theres acrylic options but I’ve never tried them.

I have got some fancy acrylic putty to do mine. Claims to be paintable in a few hours. I haven’t used it yet tho.

Not quite the same application but…

I drilled out all the knots in our pine front door and filled the holes with two part expoxy. Several years later and no cracks or issues from it. The door gets strong sunlight in the mornings and the knot sealant couldn’t cope and the knots kept weeping through the sealant and paint.

do the putty yourself. get a different decorator to paint it at a later date.

a nice day and a putty knife and you’re good to go.

Linseed. Traditional aint it.

I refurb a lot of sliding sash windows and for all glazing applications I use this.
https://www.repair-care.co.uk/product/dry-seal-mp-white/

It’s flexible and will move with the timber and not crack or split, more expensive than putty but better in every way.

I refurbed rotten sash lintels with 2-part ronseal stuff (that frankly, once I’d dug out the rot was mostly hole!) and its held up well. Putty wouldn’t have done it. For the glazing I used some glazing silicone which has been OK.

you can’t paint silicone though so don’t do that!

Wood filler for glazing windows sounds like a complete bodge to me

do the putty yourself. get a different decorator to paint it at a later date.

a nice day and a putty knife and you’re good to go.

I’m thinking this might be the best option. Can putty be left unpainted for an extended amount of time? Some of the decorators are booking out until September.

I refurb a lot of sliding sash windows and for all glazing applications I use this.
https://www.repair-care.co.uk/product/dry-seal-mp-white/

It’s flexible and will move with the timber and not crack or split, more expensive than putty but better in every way.

That reminds me I bought something similar from geocell last year but didn’t use it. I guess they aren’t breathable though, but maybe not an issue as I assume neither is gloss paint.

https://leylandsdm.co.uk/geocel-glazing-putty-310ml-white.html

That geocel glazing putty is what i used (not silicone as i said previously)

I’m thinking this might be the best option. Can putty be left unpainted for an extended amount of time? Some of the decorators are booking out until September.

No – It will crack and then let in water. a couple of weeks.

Why not get them to do everything but repaint the putty and then paint that yorself?

Can putty be left unpainted for an extended amount of time?

Yes. The recommended time to leave it before painting can be between a few weeks and a few months so extending that a bit isn’t an issue.