How can WWA windows last so long?

Tue 16 Feb 2016

I’ve lost count of the number of times people have said to me that modern wood windows don’t last – there are a lot of Jeremiahs out there. When you point to the number of Edwardian, and even Victorian, wood windows still in working order today, they’ll tell you the pine was different then. Well, we only 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.

Our mission in the UK, since the Wood Window Alliance was set up in 2007, has been to make sure our members manufacture wood windows that meet those exacting standards, to provide evidence of the windows’ longevity and to tell the story, first to specifiers and then to homeowners. 

As Dr. Richard Murphy of Imperial College London, who did the initial Service Life Assessment work, said in 2011 “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 what goes into making a WWA window last so long?

The quality and treatment of the timber

The timber has to 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.

The design

Windows will be designed with rounded weathered edges to ensure good coating adhesion and sloping surfaces to shed water.


All WWA scheme windows are 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 your home real kerb appeal!

For more information, you can download the Heriot Watt Whole Life Study (which includes Service Life, Whole Life Costing and Life Cycle Assessment) and our WWA Specification Guide