Roofs and flat roofs
What is a sprocketed or bellcast eaves, and why is the change of pitch not a sagging ridge?
A sprocket, or bellcast, is a deliberate easing of the pitch at the eaves so the last courses lie a little flatter and throw water into the gutter. It is a traditional detail, not a sagging ridge and not roof spread, and a surveyor who names it is stopping that change of angle being misread. They still cannot see the sprocket timbers without opening the eaves.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
From the pavement a bellcast can look like the roof has slumped at the bottom. The ridge can be straight and the purlins sound while the last few feet of rafter are firred to a shallower angle. That shallower bit sheds water more slowly, so the gutter position matters. A home survey can record the shape. It does not open the soffit as standard, and it does not prove the sprockets are free of rot.
If the gutter sits below the bellcast and water overshoots it, that is a gutter comment, not a failed ridge. If the fascia at that eaves is soft, that is the fascia, which is a different question from the designed change of pitch. Ask the surveyor which they mean. There is no reason to rebuild a roof because it has a bellcast. There is a reason to ask if the easing was noted as original or as a dip they could not explain.
What should you ask your surveyor?
- Is the shallower pitch only at the eaves, or does the ridge also dip?
- Did you see the gutter catching that eaves, or water missing it?
- Are you calling this a designed bellcast or an unexplained sag?
What are the typical next steps?
- Do not describe a bellcast as roof spread in a note to the seller.
- If the gutter misses the eaves, ask about the gutter, not a new ridge.
- Leave the soffit closed unless a proper inspection of the sprockets is agreed.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Do all old roofs have a bellcast?
No. Some do, especially older tiled roofs. The survey should say what this eaves does, not what the period usually did.
Can a bellcast hide a rotten rafter foot?
The shape does not hide or reveal it. The survey sees the shape. The rafter foot is concealed unless the eaves was opened.