Today’s wood windows can last a lifetime or beyond.
When you point to the number of Edwardian, and even Victorian, wood windows still in working order today, people will tell you the pine was different then. Well, we have ourselves to blame for teaching a whole generation in the 70s and 80s that softwood rots.
But, of course you only have to look at other countries, such as the Netherlands, Germany and the Scandinavian nations, to see that well engineered modern wood windows last a very long time indeed.
As Dr. Richard Murphy of Imperial College London concluded from his initial Service Life Assessment work for the Wood Window Alliance: “This research implies there is no reason why today’s Wood Window Alliance windows shouldn’t last as long as Edwardian and Victorian wood windows – a lifetime or beyond”.
The work by Imperial College London, later developed by Heriot Watt University, Edinburgh, showed a standard white softwood window made to WWA standards and with average maintenance, to have an expected service life of 56-65 years – around twice as long as the equivalent PVC-u window’s 25-35 years. The latter study included aluminium-clad and modified (e.g. Accoya™) wood windows made to WWA standards, which can be expected to last significantly longer still.
So why does a modern, factory-finished wood window last so long?
The quality and treatment of the timber
The timber should meet or exceed British Standards Use Class 3 durability, either by using a naturally durable hardwood, a modified softwood (e.g. Accoya™), or most typically, slow-growth Scandinavian pine treated with a water-based preservative. The timber will be engineered to remove defects and increase stability.
Windows will be designed with rounded weathered edges to ensure good coating adhesion and sloping surfaces to shed water.
They should be fully factory-finished to ensure accurate coverage of surfaces in accordance with the coating manufacturer’s recommendations, or otherwise a minimum of 120mu on exposed or semi-exposed surfaces and 60mu on concealed surfaces. All joints are fully coated with thermoplastic or thermosetting adhesive and all exposed end-grain sealed.
Testing and third party accreditation
Windows will be tested to meet British Standards and Building Regulation requirements, CE marked and certified by a third party, such as TRADA or BSI, or accredited by the WWA.
So next time someone dismisses timber windows because they rot, you’ll know that just isn’t true of windows made to WWA standards. The initial cost of the wood window may be higher than PVC-u, but it will last so much longer, be so much kinder to the environment and give any home real kerb appeal!
See the links below to further information on wood windows, including a video from Roger Bisby in our Wood Campus TV series.