Working environment
Site practice
Methods of handling timber on site can have a major effect on coating performance. Careless handling or storage can put stress on joints opening them out to the ingress of moisture. Exposure to the elements can lead to degradation of the surface affecting adhesion to any subsequent coating.
When handling or storing timber the following points should be considered:
Storage
- To minimise stress on joints all joinery should be stored in support frames or stacked flat.
- All joinery should be stored under cover and kept well
clear of the ground to protect it from water and sunlight
and to avoid subsequent degradation of the surface.
NB. If joinery is to be stained and has been given a factory pre-treatment coating these storage recommendations are even more important as stain pre-treatments are much more vulnerable to degradation by sunlight and moisture than conventional paint primers. - Protect hardwood especially oak and mahogany from alkaline water running off adjacent brickwork as it discolours timber.
On-site preparation
- When components have been left around on site debris should be wiped off and the components cleaned down thoroughly. Any mould should be treated with water/bleach solution or Dulux Trade Weathershield Multi-Surface Fungicidal Wash* .
- Any denatured timber should be removed by sanding and scraping in the direction of the grain.
- Chalky deposits should at least be rubbed down or better still washed and rubbed down and then rinsed and allowed to dry.
- If there are any small loose areas they should be dry-scraped back to a firm edge. Bare areas should be spot-primed and brought back to the level of the surrounding surface. If the factory priming has been seriously degraded prime overall.
Mortar splashes
- These should be removed before they have time to set otherwise they increase the moisture content of the wood. The alkalinity of mortar splashes will also stain and will affect the durability of the coating.
- Ensure that any timber cut after application of a factory-coated pre-treatment is given another pre-treatment coating to minimise deterioration. Ensure that the preservative penetrates well into the end grain and in such porous areas apply an extra coat.
- Factory-coated pre-treatment can be damaged by mortar due to alkaline attack. Make sure that all mortar especially on sills is removed quickly and that components are not left without finishing coats for long periods once installed in the building.
When joinery Is to be stained
- 1. Apply one coat of Basecoat and at least one coat of Woodstain before installing joinery into the building particularly hardwood.
- Use flexible stopping components not fillers for making good and restrict their use to nail and screw holes and serious shakes particularly on horizontal surfaces where water can collect.
- Sand down any protruding machine marks and any sharp arrises. Then apply another pre-treatment coating followed by two coats of woodstain over sills rebates and beads ensuring adequate film thickness.