How to paint doors and window frames (outdoor)
Before you start on your outdoor paintwork, you need to decide if you want to use alkyd (solvent-based) or acrylic (water-based) paint. What kind of paint should you use on a surface that’s already been painted? In principle you should use the same kind of paint that was used before. You can choose between water-based paint such as acrylic or alkyd paint that requires solvents such as turpentine. If the wood hasn’t been painted before, it’s best to use acrylic outdoor paint. This allows the surface to breathe, which means acrylic paint has better adhesion all year round.
Use good-quality brushes and rollers – these give a noticeably better result.
To paint over doors and window frames that have already been painted, you should first roughen the surface with a piece of fine sandpaper or a wire brush. This should be enough to ensure good adhesion of the new coat. It’s a good idea to make everything clean and greases-free, including hard-to-reach places. The best way to do this is to use a mixture of water, detergent and ammonia. Take care to avoid scratching the glass, as this can’t be repaired later.
The present condition of your paintwork
The water in acrylic paint can sometimes lead to softening of the surface to be painted. This in turn can cause flaking or bubbles in the paint. So it’s a good idea when using acrylic paint to first test a small area of the door or window frame. Then wait a few hours. If there is no flaking or bubbles, then it’s safe to continue using acrylic paint. In older houses you’ll often find that putty has been used to fix the windows in place. Check that the glass is secure, and repair or replace it if there are any cracks.
Condition of older paint layers
Check the condition of the existing paintwork. You can test if this is flaking or crumbling as described in step 2. But now apply 2 strips of tape, and after 3 days take a sharp a paper clip and make a deep scratch on a test area. Stick a strong piece of tape over the scratch and remove it quickly. Check if there is a lot of flaking of the surface. If this is the case, the existing paint layer won’t bond strongly enough. That means you’ll have to switch over to using alkyd (solvent-based) paint. This gives better coverage if the surface is powdery.
Overlap to protect from moisture
The method used for painting outdoor window frames and doors is nearly the same as for indoor window frames and doors. The only difference is that when you’re painting outdoor windows and doors you should overlap the glass by a few millimeters. This will prevent the entry of moisture. If you’re using putty, this can lead to cracks. The best time for outdoor paintwork is from mid-April to mid-October.
Note: be sure you don’t paint in strong sunshine; this will cause the paint to dry too quickly which doesn’t give an attractive result.
Guttering and gutter boards
Of course the kind of material used for guttering and gutter boards is an important factor in the working method – for example Trespa or other laminated boards, hardboard, wood, steel or PVC. Check which kind of paint has been used for the guttering. Old paint coats can be removed with a scraper or paint stripper. If the guttering is made of galvanized metal, don’t scrape it because that can lead to corrosion. If there are bubbles in the old paint coat because of the paint stripper, and this can’t be removed any further, you’ll have to clean it off manually with a scraper. Don’t wait too long before scraping, because if the paint stripper starts to dry you’ll have to start all over again. Then clean the wood with water, and after drying first apply a new layer of undercoat followed by a finishing coat. See also the step-by-step instructions for ‘Different kinds of paint and varnish’.