The site of the visitor centre lies 100 m back from the cliff face, commanding a splendid view of the Channel port - and catching every bit of wind from France. Making sure that the building wouldn't blow away would clearly need some thought. At the first design team meeting on site, leaning into a stiff south-westerly, we all agreed that the building should be robust and very simple, with a timber-frame structure and a grass-covered roof.
As the design developed, the only elements which changed were the columns. Timber columns are difficult to detail at the bottom, particularly external columns designed to carry bending moments into the foundations, where the timber is usually bolted into a steel shoe before being cast into concrete. It was decided to simplify this, using one material instead of three, by making the columns of concrete. They were precast, and have the simplest possible detail at the bottom, where they are dropped into a generous pocket in the foundation, shimmed to line and level, and grouted in.
The roof is heavier than normal roofs due to the grass - even Erisco Bauder's lightest system weighs 1.2k/Nm2. We decided to use Douglas Fir for the main rafters, rather than unspecified softwood, to get the benefit of its greater strength and stiffness as well as its superior appearance. This nearly came unstuck when we discovered that the recent revision of the timber code has mysteriously reduced the properties of Douglas Fir so that it is now no stronger than Redwood (it used to be 20 per cent better). However, after some leaning on the numbers and specifying the sequence of connecting the rafters to the columns, we managed to adjust the bending moments and get the answers that we wanted.
Sam Price, Price & Myers