- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 11 Apr 2018
How the substrate affects external timber doors
When external timber doors have been selected, it is important to note that they contain a number of substrate features that could affect their performance, either now or in the future. This article takes a closer look at some of these features and the affects they can have. Sometimes, simply painting or staining doors can help prevent any issues from occurring:
- Density – The heavier and more dense the species selected, the less prone it will be to absorbing moisture. The lighter the species, the more prone it will be to taking on moisture.
- Edges – The presence of sharp areas can create stress in paint films, eventually causing them to fail. Arrised or rounded edges permit film movement with minimal stress.
- Unseasoned (Green) – The use of timber that is “green” increases the likelihood of blistering and peeling in the paint. A stain will generally be more effective.
- Weathered vs unweathered – External timber doors that have been exposed to weathering prior to being finished often experience poor paint adhesion, but stains don’t tend to be affected.
- Heartwood vs Sapwood – Heartwood has better staining potential than sapwood, but both are quite suitable for being painted.
- Smooth vs coarse – Surfaces with a smooth texture are able to hold paint better than those that are coarse. Surfaces with a coarse texture, however, will provide a better performance.
- Gum pockets – The presence of gum pockets in the door can lead to resin exudation, unless they have been pre-treated and sealed. This is important for maintaining the appearance.
- Knots – The presence of knots in the timber can lead to premature cracking, staining and resin exudation. These occurrences can be avoided using knotting varnish or on manufacturer’s advice.
- Bark – If any pieces of bark, no matter how small, are allowed to remain on the door it could lead to the premature failure of any coating (including both paint and stains).
- Insect damage – Sometimes insect damage cannot be avoided. The damage must be treated or filled before finishing to avoid failure.
- Moisture range – The normal range is between 10 and 15%. Levels that are higher can be very detrimental, particularly if a solvent borne finish is used (where moisture vapour permeability is low).
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
Developments in the Future Homes Standard.
An American chimney feature with a colourful past.
Homes based on need, not ability to pay.
Historic England adds 216 entries to the 'at risk' register.
Will cycling and walking provisions be preserved?
Assembly point levels range from relative to ultimate.
Signs are pointing to a recovery for the construction industry.
Campaigning to change perceptions about American Brutalism.
Sprinkler head configurations can prioritise people or property.
Report from The Carbon Project reveals shortcomings and recommendations.
Advice on how to join the electrotechnical profession.
BREEAM Building Back Better briefing paper provides initial guidance.
CIOB conducts global search for best built environment picture.