Advice needed on order of sealing plaster, applying mastic & oiling bare wood window frames
Léa 17/07/2025 - 8.13 AM
Hi everyone,
I’m quite new to this. I’ve sanded my painted window frames back to bare wood, and patched around them with new plaster, leaving a small gap for movement.
I’m planning to caulk with Toupret Fill-Flex and finish the wood with Rubio oil. But I’m not sure about the right order:
Should I seal the plaster first with something like Zinsser Guardz or just do a mist coat? Is it better to apply the mastic onto the bare plaster, or wait until it’s been sealed or painted? And finally, should I only oil the wood at the very end, carefully masking off the mastic so the mastic can stick properly to the bare wood?
Really appreciate any advice!
Are you a tradesperson and able to answer this question?
Hello, I would paint the wall with primer, then the wood(watch out for the wood). You apply the mastic before the final painting, so that it is painted over along with the wall.
If I am plastering, I always try to remove all relevant woodwork, that way small gaps do not need to be left. I always wait until it is sealed before attempting anything else. Sealing first gives you the chance to apply your mastic and have it adhere to a fresh surface.
Get all the grubby sanding done first.
The mist coat this helps seal the plaster of its high suction then the the chalk will stick and go on much smoother. Painting walls without a mist coat will leave more trails marks from the roller and can cause pealing in the future.
When I mist I use normal matt emultion watered down roughly 1 paint / 3 water. This way you can catch those trail marks, a much better finish and cheaper with out having to buy plaster paints. I always sand the plaster first with p120 grit, why scratch up the painted wall! So many painters do this after but as a plasterer it drives me mad! There will always be water marks left.
Once walls have a coat of paint you can see if you need to fill any marks before the final coat of paint.
Do the messy painiting first then touch up the sanding of the wood cleaning of any painting splashes. Then carfuly oil and finish the woodwork last.
You dont need to use masking tape if your any good at cutting in. Tape can cause more trouble than its worth, be very careful to buy the lowest adhesive tape if you do so not to peal of the new paint. As in a decoraters store for advice, like Brewers or dulux.
