Hi @suetang,
Thank you for your question about painting a timber frame in your home.
Would it be possible to get some photos of the frame that you're looking to paint? This will help our members to visualise the project and offer their best advice.
Are the frames already painted?
If this is why you'd like to know how to tell whether it is oil or water-based paint, this can be done by using some Methylated Spirits on a rag. Wipe the rag on the surface in a circular motion. If the cloth is stained with the wall colour, it is water based paint. If it is not stained, it is oil based paint.
To get the best result, it's always a good idea to sand the timber back to remove any dirt, dust or debris and then use a high-quality primer. I'd suggest Zinsser 1L Bulls Eye 1-2-3 Undercoat Primer Sealer Stain Blocker as it can be used both indoors and outdoors, is great over existing paint and will stop any colour from the timber coming through the paint.
Once primed, apply 2-3 coats of your chosen paint.
You might like to have a look at How to paint like a professional for some further guidance.
Let me know if you have any further questions or need a hand uploading images, I'm happy to help.
