Design

Good design detailing is one of the main methods of defence as it can do much to reduce the effect of moisture by minimising its contact with the wood.

The following aspects apply equally to both stains and paints. Stains are more likely to show problems caused by design defects while paints go some way towards covering them up. However eventually paint will fail by flaking off, dramatically highlighting poor design detailing.

1. Where joinery is in contact with brickwork, concrete and similar materials vertical and horizontal damp-proof courses should be so placed as to prevent moisture penetration at contact surfaces.
2. Windows should be set back from the outer edges of walls so that water does not run from brickwork onto the windows. This design feature also provides a measure of protection against weathering generally.
3. Joinery is frequently attacked by moisture on the internal surfaces. This is often due to modern living conditions (such as the installation of central heating addition of loft and cavity-wall insulation erection of porches increase in the number of people living in a building etc). Extra ventilation could help to solve the condensation problem.
4. At external joints between frames and walls use mastic and sealants and provide drainage for joints.
5. Always use glazing blocks and spacers.
6. Provide slopes to allow water to run off and add drips to ensure that water does not run into walls - the result is a very significant improvement in surface-coating performance.
7. Avoid the use of water channels drilled through wood as they direct water into wood.
8. If some types of pivot windows are opened to a reasonable degree a reservoir situation is created. If possible change the design.
9. Vertical beads should be cut back half an inch from corners to allow water to drop away from joints.
10. Ensure that exterior-grade plywoods (WBP) are used externally. When choosing the face veneer remember the problems of checking on the outer veneer.