Keep aware of security all the time; don’t leave doors and gates open unattended. Don’t leave brushed unwashed. Don’t leave a mess for the occupants of the property.
Put cloths/plastic sheets down everywhere before starting work.
Paint all parts of the window (especially the bottoms of Sashs and corners of sills) only a tiny gap is needed to let water in, in which case it’s better not to have painted the window at all (as it would have been able to release the moisture again through the unpainted surface.
The window must be painted leaving all water to run off againand no so pooling occurs, sills must slope away from the building and must be altered if otherwise. An angle grinder or belt sander can be handy for this job.
All cracks in the woodwork must be sealed with a flexible paintable Polymer type silicone like CT1, The Works etc (not normal silicone), since it is long lasting and flexes with the timber, before undercoating with waterbased undercoat. All such silicone must be painted since it deteriorates under UV light. If cracks don’t open up again after painting water won’t get in causing rot.
All joints between glass and putty/timber; timber and timber; timber and masonry must be fully sealed with flexible paintable Polymer type silicone, double check after the work that there are no gaps to let in water, especially the bottoms of glass panes and all around the sills.
Check with a moisture meter that the windows are well below 18% moisture content (only paint after two weeks of warm dry weather, not if it’s just rained, it’s best in late summer so the walls are dry too). When over 18% moisture cannot leave the timber as vapour, and too much escapes causing blistering of paint in heat and freezing and cracking of paint in winter. If the timber is wet expose bare timber and wait for two weeks of hot dry weather and test again.
Moisture in the timber is the main problem for windows; a wooden antique sitting in your living room can remain good for hundreds of years.
The vertical insides where sashes run up and down should not be glossed (hindering their movement), however they must be glossed for a few inches from top and bottom, the rest should be left and waxed.
Make sure the bottom of drip bars/grooves and weather bars are not forgotten; they must be cleaned, dry, sanded, rubbed down, primed, undercoated and glossed as well. They are especially important as water clings here for longer than anywhere else on the window soaking up moisture into the timber if unprotected.
The room side of the windows must be painted in the same way (when dry with Polymer Silicone at joints) at the same time as the outside; with moist warm air condensing constantly on the cold internal surface of windows more moisture will be coming from inside than out.
Several thin coats are better than one thick coat, watch out for drips and pooling.
Print off a diagram, from the Web, on the order in which to paint the parts of a door/window to leave a good finish and follow this when painting.
The most important thing is preparation! The most important preparation is to first completely clean the window and existing paintwork/timber! (Sometimes after cleaning it’s found that the window didn’t actually need painting) Sugar Soap and a course scourer should leave the necessary ‘key’ (slight abrasion for new paint to cling to). Tesco’s bathroom cleaner with bleach, which you leave to work for five minutes, is good at attacking dirt. All dirt in the corners must be removed by attacking with spounge and water; these will be weak spots causing subsequent gaps in the paint coating otherwise. After cleaning the residue must be removed with a towel. And the window must be left to dry fully.
Use a Water-based (dries quicker) Moisture Vapour Permeable ‘MVP’ paint system like the one from Dulux or Ridgeons. CT1 and other Polymer/MS Silicone need covering with water-based paint first, and take ages to dry in contact with Oil-based paint, but will eventually.
Old windows need; 1, Cleaning and removing rot/bad timber and loose paint 2, Drying 2a, checking moisture content is below 18% 3, Sanding 4, Dusting and rubbing down with a cloth 5, Priming, 6, Filling with Dulux weathershield flexible (grey) filler 7, 8 waiting a day for filler to dry, 9 Sanding and priming of filler 10, Polymer Silicone sealing around all joints 11, undercoating 12, Second undercoat 13, Glossing. Window must not get wet all of this time – if it does scrape off again and wait two weeks of hot dry weather! (Cover window with waterproof sheet if there’s a danger of rain).
It’s good to remove all old paint with a heat gun and scraper if there is time, taking it back to the bare timber. The heat dries the old timber, taking moisture content below 18%, and the old paint won’t now cause a barrier to moisture vapour exiting the timber after the new MVP paint is on.
The Dulux Weathersheild system needs two coats of undercoat after primer on bare timber.
Do not seal any timber with wood hardener as it blocks the exit of moisture vapour from the timber, sealing in moisture, as moisture builds up it will eventually cause failure of the paint coating, and doesn’t flex with the Timber. Instead of wood hardener replacement treated timber or preferably hardwood or WBP Ply or should be used, sealed in with a Polymer Silicone so cracks don’t open up (or flexable filler)
Do not use the standard two part wood filler or anything else that doesn’t flex or breath with the timber, it will start cracking after a few years or less. The best thing is to replace with dry hardwood/ WBP Ply and seal joints with a paintable Polymer Silicone type flexible/paintable product.
Old Glossed surfaces must be sanded/keyed to prepare it for waterbased undercoat/gloss, or it won’t stick. Also cleaning is needed to de-grease the surface including around glass pane or new paint won’t stick.
Expanding foam can be used to quickly fill large gaps or fix in replacement bits of timber, some types dry in half an hour. It flexes in large quantities and is durable being Polyurethane.
Avoid painting in direct sunlight, this causes the paint to dry to too fast on the surface creating a shell which will crack later and can create a wrinkly effect . The paint needs to dry naturally in its own time to harden correctly. Do not use heaters to dry the paint faster.
Do not do any painting below 50C, Surface temperature, which is most important, can be checked with a laser thermometer.
If the window has no drip bar/groove or it’s damaged, it needs to be replaced by nailing on another piece of timber to the front of the sill to act as a drip bar. As done on the Abbey house window above the front doors.
Windows close to the ground suffer from rain bouncing back up from the ground. The underneath of sills here is even more important.
You only need to prime bare timber and filler. Leave paint to dry as long as it says on the tin.
Use the tower scaffold rather than expensive scaffolding if possible, that’s what it was bought for (costing £2000). Work on higher windows first as dust will fall on painted lower windows.
There’s no point decorating windows if the walls around the windows are soaking wet, which they shouldn’t be in summer, but there could be other sources of damp than rain. There’s no point decorating a window if it’s damp inside or will be made damp by the surrounding walls. Painting in such cases will trap in the damp causing more damage. As in the Abbey house laundry room window which was left for that reason.
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