How to paint sash windows
You should paint sash windows about every 4 years to keep them looking great!
When to paint really depends on the amount of weather they get.
Before painting sash windows there’s a a few things you need to check first.
- Check the window putty, if it’s loose then remove as much as possible.
- Check for rot, any rot should be removed and whatever is left treated with a wet rot hardener.
If there’s any rot about the windows then you will need to to remove as much of this as possible. If it’s not too bad you can use a wet rot hardener to strengthen the wood before filling over. A small amount of rot can be repaired without the need of a carpenter
To paint your sash windows you'll need to make sure you have all the tools necessary.
You’ll need the following tools –
- Screwdriver
- Tungsten carbide scraper (if you can find one!)
- Filling knives 2″ & 1″
- Putty knife
- Sandpaper grades 80, 120, 150, 180, 240
- Sash paint brush
- Small paint kettle
You’ll need the following materials –
- Aluminium wood primer
- 2 pack filler
- Linseed oil putty
- Undercoat
- Top coat – Gloss is hardest wearing
- Methylated spirits
- Masking tape
Remove any loose putty and clean out the area exposed. This might be damp and if so should be left to dry out.
Scrape out any loose rotten wood and leave the sash window exposed to the air for a couple of days (hopefully it doesn’t rain!), this will dry it out some more for you. After a couple of days have passed you can now apply some wet rot hardener to the exposed rotten areas. The wet rot hardener does exactly what it says on the tin – it makes the wet rod hard. If it’s hardened you can fill it, if it’s filled without the wet rot hardener then the filler won’t bond with the old rotten wood, the rain will get in again and just make matters worse!
Window putty should be replaced using a putty knife.
Once all the holes have been filled up you can now start sanding. You don’t need to remove all the old paint but you do need to give it a good key. What we mean by a good key is to remove the sheen from the old paint. If you don’t key the surface and instead just paint straight over the old gloss then you can look forward to the paint flaking and peeling away within no time at all. When you have all the sash windows rubbed down you should then give them a good dusting followed by wiping down with methylated spirits. The methylated spirits will evaporate away leaving no residue.
Linseed oil putty needs to cure before you paint over. It can take up to 6 months to cure properly! An alternative is 2 pack wood filler, cures in about 30 minutes and ready to paint!
Once all of this has been completed you can start spot-priming all exposed wood and fillers with an aluminium wood primer. The aluminium wood primer is a silver-grey primer that will help to protect your woodwork from the elements.
Once the priming has been completed and left to dry, usually overnight, you can then start undercoating. For this sash window, we used two coats of an oil based undercoat followed by one coat of an oil based gloss, in this case, it was Sikkens Rubbol Satura.
This is one of our Master Painters preparing & finishing a sash window
The actual painting is the easy part! Before you paint you’ll need to remove sash ring hooks, fasteners etc.
Once this is done push the bottom sash up to the top and pull the top sash down to the bottom. This will allow you to paint the top of the bottom sash. You can follow the sequence in these pictures.
