Buying a House With Roof Spread

Purchasing a home is a significant investment, so you should always consider the condition of the property. One structural issue you may come across is roof spread. Whether it has been flagged in a survey report or you have noticed signs yourself, understanding the potential implications is important before you buy.

Roof spread can affect older and altered properties, particularly where the roof structure does not have adequate support or restraint. The severity varies: some roofs have long-standing movement, while others may need significant structural repairs.

If a survey identifies possible roof spread, further investigation can help establish its cause, whether movement is ongoing and what work may be required.

Need more help? Read our guides on structural movement in a house, roof surveys and negotiating when buying a house.

What is roof spread?

Roof spread happens when the roof structure does not adequately resist the outward thrust of the rafters. Because the weight of the roof pushes down and out, a lack of restraint allows the lower ends of the rafters and the tops of the supporting walls to move outwards. As the walls bow, the roof itself may sag or become visibly distorted.

A pitched roof is supported by a framework of rafters and other structural timbers. The rafters meet near the ridge of the roof, while their lower ends are supported at the eaves. Ties, ceiling joists, and other structural members are specifically installed to resist these outward forces.

Older roofs often use traditional timber frameworks, while many newer roofs use prefabricated trusses designed to distribute loads through a series of connected members.

Where the roof structure does not have adequate restraint, the resulting forces can severely affect the supporting walls. The appropriate repair depends on the cause and extent of the movement and may involve strengthening or replacing parts of the roof structure.

How common is roof spread?

Roof spread is most commonly found in older properties, including Victorian and Edwardian houses, but the age of a property alone does not guarantee a problem.

Traditional roof designs rely on the correct positioning and condition of their structural timbers. If ties or other supporting members are inadequate, deliberately removed (such as during a poor loft conversion), or damaged by rot, the rafters will exert excessive outward pressure on the supporting walls.

Changes to the roof covering can also trigger spread. For example, replacing a lighter original slate roof with heavier modern concrete tiles can drastically increase the load on a structure that was never designed to support it.

The signs and causes of roof spread

Detecting roof spread can be challenging. Some warning signs may be visible during a viewing, but they do not confirm the cause on their own.

Signs to look out for include:

• A sagging roofline: A dipped ridge line, uneven roof slopes, or visible distortion is often the most obvious external sign.
• Bulging walls: External masonry walls that appear to bow or lean outwards, particularly near the top course of brickwork.
• Cracking: Deep horizontal cracks near the tops of external walls, or diagonal cracks around upper-floor windows and doors.
• Sticking doors or windows: Frames on the upper floor that have shifted out of square and become difficult to open or close.

Roof spread occurs when rafters are not adequately restrained, but a sagging roof or cracking alone does not automatically prove that roof spread is present. A surveyor can assess the visible signs and recommend further investigation.

If a survey identifies potential structural movement, you must seek advice from a structural engineer to determine the exact cause and the appropriate remedial work.

Implications of roof spread

Buying a property with roof spread has several major implications that must be addressed before exchanging contracts.

Structural stability: Significant or ongoing movement will compromise the roof structure and supporting walls. A suitably qualified professional must assess whether the movement is ongoing and what remedial work is required to stabilise the building.

Repair costs: The cost may be relatively manageable if the problem can be addressed with localised timber repairs. However, extensive work could involve completely rebuilding the roof structure or replacing the bowed masonry walls.

Mortgage considerations: If you need a mortgage, your lender will almost certainly require a satisfactory structural engineer's assessment before agreeing to lend. Some lenders may apply a retention (holding back funds) until the repairs are completed.

Insurance: Existing structural problems or a history of major repairs may affect the availability or cost of buildings insurance. Always contact insurers to check if cover is available before deciding whether to proceed.

Roof spread repair costs

There is no single price for repairing roof spread. The final cost depends entirely on what has caused the movement, how far it has progressed, and whether the work involves the roof timbers, supporting walls, or the external roof covering.

Possible remedial work may include:

• Adding or repairing structural ties (e.g., collar ties) to prevent further outward thrust.
• Strengthening or repairing damaged rafters and timber affected by rot.
• Repairing or replacing damaged wall plates.
• Addressing damaged masonry or completely rebuilding walls that have moved too far outwards.
• Removing and replacing the roof coverings to access the structure (often necessary when swapping heavy concrete tiles back to lighter slate).

Before agreeing to buy, ask for a written assessment of the work required and an itemised estimate from an appropriately experienced contractor. Do not rely on a standard roofer's quote for replacing tiles as an estimate for fixing underlying structural roof spread.

Should I buy a house with roof spread?

You do not necessarily need to walk away from a property just because a survey has identified possible roof spread. However, you must understand the extent of the problem and the likely cost of putting it right before exchanging contracts.

If you are committed to purchasing the property, follow these steps:

1. Get a detailed survey: Ask a surveyor to assess the visible signs. A structural engineer will likely be required to identify the cause, assess the extent of movement, and specify repairs.
2. Establish repair costs: Obtain a written estimate from a suitably experienced structural contractor based on the engineer's exact recommendations.
3. Check the mortgage position: Speak to your mortgage broker immediately to confirm if the structural concerns will result in a mortgage retention or a declined application.
4. Negotiate the purchase price: Use the structural engineer's report and the contractor's repair estimate to negotiate a price reduction. Read our guide on how to negotiate when buying a house.
5. Check buildings insurance: Contact insurers to establish whether cover is available and what conditions or exclusions apply regarding the existing movement.

Buying a house with roof spread? We can help

If your survey has identified possible roof spread, it is crucial to understand the extent of the problem before committing to the purchase. A further survey or structural engineer's report can help establish the likely repairs and protect your investment.

At SAM Conveyancing, we can help you arrange a comprehensive property survey and connect you with the right professionals so you know exactly what you are buying.