Timber in the frame - dealing with timber window and door frames


Timber door and window frames are an increasingly popular option in both new builds and conversions. These can provide a premium finish making projects stand out from the crowd. However, the durability of timber compared to other materials means their use is not without problems.  We consider the potential issues and how these can be avoided.


Window and door frames form part of the waterproof envelope so when using timber frames, in particular softwood units the frames must be robustly constructed and protected. They must also perform to meet the minimum requirement for durability and weather resistance of at least 15 years.


What are the potential issues?

Problems with the construction, maintenance and protection of the frames can lead to a number of issues;

  1. Inadequate finishing of the frames, for example, lack of primer coat to rebates prior to glazing installed. This increases the potential for early deterioration of the frame as well as water ingress.

  2. Poorly constructed frames, frames made from individual pieces of untreated soft wood timber that has only been pinned together.

  3. Frames and opening lights warping due to inadequately sourced and treated timbers, or frames that have been left exposed and unprotected for long periods before installation.

Recommendations when dealing with timber frames

The number of claims for defective timber framed windows and doors have increased in both conversion projects and new build housing. The cost to remediate can in some cases result in complete replacement being the most cost-effective solution.


For warranty purposes, timber window and doors must be checked to ensure they are:

  • Adequately manufactured to meet BS 644.

  • Have evidence of declared weather tightness testing.

  • Have CE marking and labelling details present.

  • If in the case of a window or door being ‘one of a kind’ frame for a conservation project a CE marking is not required; full specifications are required to determine how the frame will be manufactured to meet the durability and weather resistance requirements of the LABC Warranty Technical manual.

  • In the case where the frames are made by a small joinery work shop; adequate verification of meeting the standards is obtained.

  • Frames must be adequately preservative treated and properly decorated. Details of ongoing maintenance should also be identified for the particular environment exposure of the project.

    Make sure your timber frames are adequately constructed and finished

    To ensure long lasting quality make sure your timber is adequately constructed and treated.


    Don’t skimp on the primer coat or preservative! This principle also applies prior to installation as frames left exposed and untreated for long periods of time before installation are destined to degrade quicker.

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