Timber frame, the way Britain builds it
North of the border most new houses are timber frame, and a growing share in England are too. The walls arrive as factory panels: studs 140 mm deep at 400 mm centres, OSB on the outside face, a breather membrane stapled over it, and the cavity left open for mineral wool and a polythene vapour control layer to go in once the house is weathertight. The estimator counts the same parts whether they are cut on site or in a factory, which makes it a fair check on a panel supplier's schedule.
Every figure on this page was written in millimetres and metres, the way a British drawing is dimensioned. With imperial showing, the same house reads in feet, rounded to the figures a North American framer would use, and the list follows.
The foundation
The ground floor here is a 150 mm ground-bearing slab inside a strip footing 600 mm wide and 225 mm deep, at the bottom of a trench taken a metre down, the depth commonly asked for on shrinkable clay; trees nearby can push it deeper, and your warranty provider or building control will say. A British slab sits on hardcore and a damp-proof membrane with insulation over or under it, none of which is a row here: only the concrete, the mesh and the edge formwork are counted.
Cladding and roof
Vertical larch boards with cover battens are counted across the whole outside face, because the boards round each window are cut from full-height lengths, and the row says so. The breather membrane comes from the wrap row, at the outside face less the openings.
At this pitch, about 34°, the roof is concrete interlocking tiles on battens, the covering most British houses of this kind carry. The tile row takes Marley Modern at its maker's gauge and cover, so the tiles, the batten courses on each slope and the ridge tiles are counted from the slope area and the gable's edges; the breathable underlay under the battens, the eaves ventilation and the verge and ridge fixings are not rows of this family yet, and the pitched roof re-covering page lists them.
What to check
Building regulations set the wall's thermal performance, and a 140 mm stud filled with mineral wool usually needs insulated sheathing or a service void lining as well to meet current targets; neither is counted. Fire stopping at the floor zone and cavity barriers around openings are also outside this list, and so are the intermediate floor joists, which the floor joist page counts from the floor's size but this estimator does not yet draw.