Lack of support in the main roof structure

Antill & Co. Chartered Surveyors carried out a RICS Home Survey Level 3 (RICS Building Survey) on behalf of a client purchasing a four-bedroom extended and modernised 1920s detached house located in Nutbourne, Chichester, West Sussex, PO18.

The survey highlighted several defects, one of which was inadequate support to the purlins of the main roof structure.

From ground level, externally, the roof appeared generally even, with no indication of significant sagging or distortion. As part of the internal inspection of the roof structure, our surveyor entered the loft and carried out the inspection. The roof structure is a traditional timber cut and pitched roof type as shown in the diagram below.

This traditional design comprises timbers cut to size on site, rather than the more modern trussed rafter roof structures from around the 1970s onwards, which are usually built off-site.

The 1920’s roof structure, at this property, is made up of various timbers shown in the diagram above. However there is inadequate support to the purlins, the horizontal timbers - shown as red-squares in the cross-section drawing - that run the length of the roof and support the rafters, in some areas as shown in the photograph below. The supporting struts and hangers are missing and it is unclear whether they were installed originally.

In this case we recommended additional support is provided to the purlins, particularly to the end sections. This will involve the addition of some struts and hangers by installing timbers secured underneath the purlin, to carry the load of the purlin down onto a suitable beam.

We were provided with a copy of the survey undertaken on behalf of the current homeowner when they originally purchased the property. At that time, the property was unmodernised and had several issues.

The current homeowner addressed many of the issues highlighted in the survey report, which is positive. One of the issues raised was replacement of all the roof battens and slates and installing under-felting, which has been carried out.

The white under-felting can be seen in the photograph above. The report also highlighted the same support issue with the roof structure and advised it should be upgraded at the time the re-roofing works were undertaken. This aspect was not addressed.

If the roof structure is not adequately strengthened, the roof is at risk of collapse which may cause further damage to the property and poses a safety risk to occupants and those nearby. Apart from alerting the purchaser to this significant safety issue, there is the cost of installing additional struts. In this case around six were required at an estimated cost of £200 per strut, including fitting, equating to £1,200 in total.

The RICS Home Survey Level 3 highlighted £1,200 of remedial costs on this issue alone that our client would have otherwise been unaware of prior to purchase. This valuable insight provided our client with the opportunity to revise the purchase price of the property prior to exchange of contracts and avoided the discovery of costly issues after moving in. Forewarned is certainly forearmed.