Roofs and flat roofs
A scarfed purlin joint is opening and the prop under it lands on a ceiling joist. What load path ends on that joist rather than on a wall?
The load path that ends on the ceiling joist, rather than on a wall, is the one through that prop. The scarfed purlin joint is opening, and the timber shoved underneath it stops on a ceiling joist. The purlin is trying to hand load to that joist. A ceiling joist is not a wall. The survey has seen the open scarf and where the prop lands. It has not measured the load, tested the ceiling, or found a bearing that actually reaches masonry.
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?
A scarf is a lengthening joint in the purlin. When it opens, the two lengths are no longer acting as one continuous timber, and a prop under the joint is being asked to help. If that prop stops on a ceiling joist, the load is offered to the ceiling, not down a wall. The joist and the plaster can crack or dip. The survey can see the open joint. It cannot weigh the load or say the roof is failing.
A structural carpenter can say whether the purlin needs a proper bearing down to a wall, a repair of the scarf, or both, and whether the prop is doing more harm than quiet support. Do not treat the prop as a finished repair because it is tight today. Tell the solicitor the report shows load arriving on a ceiling joist. The home survey has not specified a new wall, a steel, or the removal of the prop.
What should you ask your surveyor?
- Which purlin scarf is opening, and how does the gap show?
- Does the prop under that scarf land on a ceiling joist rather than a wall?
- Did you see any bearing of that purlin that does reach masonry?
What are the typical next steps?
- Read the prop as a load path onto a ceiling joist.
- Ask a carpenter where the purlin load should land.
- Do not treat the prop as a designed support to a wall.
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
If the scarf was nailed, is the joint still continuous?
Nails do not prove the scarf is still acting as one timber. The survey saw the joint opening, which is the opposite of a tight scarf. It did not test the nails and it did not measure slip. A fastened joint that has opened is still an open joint. Continuity was not demonstrated on the day.
Will the ceiling joist be unharmed because the prop looks tidy?
No. A tidy prop can still deliver purlin load onto a joist that was not built as a roof support. The survey saw the prop stop on that joist, not on a wall. It did not calculate the load and it did not inspect the plaster from a structural test. Neat timber is not a wall.