The baseboards are of an open-frame design - the framework is fixed at the layout's lowest level (approx 70cm off the floor). The storage yard is laid directly onto the baseboards, whilst the visible portions of the layout are built up using risers from the framework.
To attach electronic components (etc.) a board is run along the back of the framework between the legs.
The restricted access to the attic imposed a maximum size limit on the baseboards - each unit is a maximum of 60cm by 120cm. This should ease removal of the layout if there is a need to move house.
The framework is made from 34mm by 44mm Planed Square Edge (PSE) timber. The timber is used in portrait (44m high by 34mm wide) for maximum rigidity. Each framework unit is screwed together using countersunk 4.0 x 60mm wood screws.
The component board is 18mm by 144mm PSE, screwed to the legs using countersunk 4.0 x 40mm wood screws, again in portrait (144mm high by 18mm wide)
Individual baseboard units are linked using M6 x 75mm carriage bolts.
The storage yard is built from 12mm thick MDF
A common depth of 60cm is used for most of the layout except where space is very tight. Unit lengths of either 60cm or 120cm (with a cross-brace at 60cm) are used.
