Painting - preparing wooden doors and windows

basically sound paintwork - stripping the paint

Good preparation is essential to achieving a good paint finish on doors and windows. The amount of preparation required will depend upon the state of the existing paintwork; whether it is basically sound or if it has deteriorated so that there are large areas of lifting or flaking paint.

WARNING: Where the existing paint is really old (i.e. 1960's or earlier), extra care needs to be taken as the paint may contain lead - avoid mechanical and heat methods of stripping these paints (they could produce lead dust or fumes) and wear an appropriate breathing mask. Seek guidance to ensure the health of you and your family is not effected.

Basically sound paintwork

Where the paint is basically sound, any small defects can be rectified without resorting to stripping the paint from the whole item. The whole process of preparation such a door/window is:

Remove all door/window furniture except any hinges.
Brush down the door/window, make sure any dirt on the top is removed.
Make good any small defects, typically:

Dents, disused screwholes etc - remove any cracked paint from around the hole. Rub down the surrounding area to clean up the surface. Use a paint brush to remove any dust from the hole and fill it using a wood filler. Powder filler mixed with paint (often referred to as Swedish Putty) will produce a strong filler which will adhere well.

Paint blisters - remove the blister and any cracked paint from around it. Rub down any paint left behind the blister to bare wood and fill to the level of the surrounding paint with a suitable filler (such as Swedish Putty). Don't try to rub down the paint edges to get a smooth finish with the base timber, this will show up when finally painted.

Visible knots - gently use a blow torch or heat gun to remove the paint from over the knot and to draw out the resin from the wood. Once it has cooled, scrape off as much remaining resin as possible and rub down using glass paper. Apply at least two coats of Knotting compound over the area of the knot in accordance with the manufacturer's instructions. Fill any voids in the knot and the surrounding area with a suitable filler.

Once the filler has cured, rub down using glass paper to get a smooth finish.

Providing none of the timber is exposed, apply a coating of undercoat over the filler and, once dry, smooth down with a fine glass paper, feathering the edges onto the surrounding paintwork. If timber is exposed, apply a coating of primer and feather that into the surrounding area before applying the undercoat. NOTE: The undercoat may not be necessary if the final coat will be a 'Single Coat' paint although it does help to disguise the repair.
Wash down the door/window using warm water with decorator's Sugar Soap (or detergent) and allow to dry.
If the original paint is very rough, use a medium glass paper (grade 120) to smooth the surface.
Use a fine glass paper (grade 240) to give the surface a smooth finish suitable for painting.

Deteriorated paintwork

Where the paint on the door/window has deteriorated, with areas flaking off or lifting, it is best to completely strip the old paint back to bare wood. The procedure is as follows:

Remove all door/window furniture except any hinges.
Strip the old paint using a chemical paint stripper, blow torch or heat gun.

Using a chemical paint stripper - follow the manufacturer's instructions, use plenty of newspaper (or other protective material) to protect the flooring and surrounding areas. Keep the area well ventilated.

Start at the top and work downwards using a scraper to lift the paint off once the stripper has caused it to lift.

Really thick layers of paint may need more than one application of paint stripper. A small ball of wirewool can be used to remove any small, stubborn areas of paint.

Some old priming paints are little affected by some chemical paint strippers, these are generally only very thin coatings and can be left and just rubbed down with glass paper.

Once all the paint has been removed, the woodwork needs to be washed down with plenty of warm water (or as directed by the manufacturer) to remove the chemical stripper and to neutralise it.
Using a blow torch - keep moving the blow torch nozzle across the surface about 75mm (3 inches) away from it to avoid scorching the wood.
Do not use a blow torch near to glass (as it will cause the glass to crack), plastic or combustible material, use a chemical stripper on these areas.

Starting at the top and working downwards, strip the paint from the mouldings first and then move onto the larger areas.

Once the paint has started to lift, use a scraper to strip it off - have a suitable container to hand so that the hot paint can be collected (once cooled, the paint can become hard and brittle - treading on it will just cause lots of dirty dust).

Using a heat gun - use a heat gun in the same way as described above for a blow torch and taking the same precautions.
Use a medium glass paper (grade 120) to smooth the surface wood and to remove any last pieces of paint - don't worry about any paint in cracks etc.
Use a fine glass paper (grade 240) to give the surface a smooth finish suitable for painting.