This technology is usually relegated to warehouses, but Hawkins\Brown make it stunningly beautiful.
Wikipedia tells us that portal frames are a very efficient construction technique to use for wide span buildings. "Portal frame construction is therefore typically seen in warehouses, barns and other places where large, open spaces are required at low cost and a pitched roof is acceptable." Even when made of wood, they are pitched as an economical solution.
That is why this new swimming pool in London by Hawkins\Brown is such an eye-opener. When the Portal Frames are made of glue-laminated wood (Glulam) they are anything but utilitarian; they are gorgeous.
Portal frames work because they have very strong, rigid joints that transfer the bending moment from the rafters to the columns, which are often deep at the top and tapered as they get closer to the ground. At the Freemen's School in Ashtead, the columns stay the same depth all the way down, becoming a wonderful louvre feature that is used to support seating.
Their depth does wonders for the quality of light, as does the white stain on the wood on the columns, rafters and the CLT roof. Adam Cossey of Hawkins\Brown tells Alyn Griffiths of Dezeen:
Freemen's School's new swimming pool is a welcoming retreat that engages with the mature woodland setting through the use of natural materials and colour schemes. The deep columns of the all-timber construction and wrap-around glazing, which afford direct views from the water into the woodland, give the sense of swimming amongst the trees.
Wooden portal frames have been used for pools before; they stand up better to the moisture than steel does. According to Dezeen,
The chosen construction method allowed the structure to be prefabricated off-site and then assembled in just over three weeks. This meant the entire project from detailed design to completion took just one year. In addition to providing a warm and natural finish that echoes the surrounding trees, the timber surfaces are robust, thermally insulating and corrosion resistant.
But they never looked like this, where they change dimensions as the roof slopes lower to one end, "offset and staggered along the building's length to create a dynamically shaped roof, with its highest point at one corner signalling the location of the main entrance."