Painting wooden sash windows

Before painting wooden sash windows, they need to be prepared as explained on our "Preparing wooden doors and windows for painting" page.

The following guidelines apply when applying Primer, Undercoat or Topcoat (or a combined paint). After applying Primer or Undercoat, the surface should be lightly rubbed down using a fine glass paper (at least 240 grade) to remove any dust etc which may have been attracted to the paint - do not rub so hard that the wood grain is exposed.

Painting a sash window can seem an awkward task as there are lots of small areas of timber and the inner sash obstructs the outer sash. The secret is in moving the sashes as you work to expose the unpainted areas. The description below refers to painting the interior of sash windows, a similar process is followed for external painting, it is easiest to do this at a separate time especially if painting windows above ground level.

If you find it difficult to paint a neat edge onto the glass (Primer and Undercoat should not go onto the glass, Topcoat should lap onto the glass by a small amount (1 or 2 mm)), the glass can be protected using masking tape. Make sure that any masking tape is pressed firmly onto the glass (otherwise paint may creep under the edge) and that it is removed before the paint is fully dried (otherwise removing it may lift the paint). Alternatively, use a piece of straight edged strip against the glass as you paint to protect it - such shields are available from DIY stores but a 'home made' shield of just a strip of stiffish plastic will do just as well. If you do get paint on the glass, leave it until it dries and then scrap it off.

Start by raising the inner (bottom) sash, and lowering the outer (top) sash, this will expose at least the lower half of the outer sash below the inner sash.

Using a fairly small paint brush (12 to 25mm (½ - 1 inch)), start by painting the glazing bars of the outer sash (1 and 2), then the lower cross bar (3) and finish with the two side rails (4 and 5). The areas being painted tend to be fairly small, so do not pick up too much paint on the brush and spread it out well.

Slide the inner sash down, and slide the outer sash up - use the unpainted cross member to pull the outer sash up - to expose the top half of the outer sash above the inner sash. Finish painting the outer sash - start by painting the glazing bars (6 and 7). then the upper cross bar (8) and finish with the two side rails (9 and 10) brushing the paint to blend it with the previous painted areas.

Now to paint the inside sash which is fully exposed so should not cause a problem, if necessary move the inner sash up slightly to enable the bottom of the sash to be painted. Start with the glazing bars (11 to 14), followed by the upper cross bar (15) then the lower cross bar (16) and finish off with the side rails (17 and 18).

Leave the sashes in the open position until the paint has dried.

Paint the surround after the paint on the sashes has dried. Shut the window and paint the exposed areas of the runners, do not paint the pulley or cords. Leave the sill until last and lift the lower sash to give access to it.

Paint the rest of the frame working outwards.