Floor plan is the starting point, not the answer. Roof cost is decided by six headings, and only two of them are fixed by the building.
The six drivers
- Geometry — hips, valleys and dormers add cutting, flashing and labour
- Pitch — steeper means more surface, and the difference compounds with overhangs
- Covering and gauge — the widest product choice, from light steel to heavy tile
- Accessory density — ridges, gutters, skylights and penetrations
- Site — height, access, occupancy and distance from the supplier
- Programme — weather windows and working around occupants
Where you save without regret
Simplify the roof shape at design stage — a plain gable is dramatically cheaper per square than a multi-valley roof and sheds water better. Choose the covering on lifecycle cost, and never thin the gauge to close a budget gap.
Where “saving” costs
Under-quoted accessories, short laps, skipped underlay and unskilled fixing all cost nothing upfront. They are the difference between a roof that lasts thirty years and one that is opened up by the third long rains. See the full roofing cost guide.