Why are rental properties with flat roofs considered more specialist?

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Buy to let mortgage lenders often consider a building with a partly flat roof more "specialist" or higher risk than pitched tiled roofs, due to several practical and financial concerns:

1. Durability and maintenance

Flat roofs are generally seen as less durable and more prone to weather-related issues, such as water pooling and leakage. Over time, this can lead to structural problems, damp, or expensive repairs, all of which reduce the property's attractiveness as security for a loan.

2. Lifespan of materials

Flat roofs tend to use materials like felt, rubber, or GRP (glass-reinforced plastic), which typically have a shorter lifespan than tiled roofs. This increases the risk of needing significant repairs or replacement during the mortgage term.

3. Insurance considerations

Properties with flat roofs can be more expensive to insure, or in some cases harder to insure at all. Insurers view them as higher risk for claims, especially related to water ingress (leaks, damp) and storm damage.

4. Resale and letting market

A flat roof may make a property less desirable to potential buyers or tenants, especially if it covers a large area. That can affect the property’s liquidity (how easily it can be sold) and rental potential, both of which concern lenders.

5. Survey and valuation risk

Surveyors may downgrade the condition rating or flag the flat roof as a potential defect, which may affect the lender's willingness to proceed. In extreme cases, the lender may require a specialist roofing report before issuing a formal mortgage offer.

6. Proportion of flat roof

The concern increases with the percentage of the roof that is flat. A property with a small flat roof extension is generally acceptable. But if more than 25–30% of the roof is flat, some lenders may either decline the case or require additional scrutiny.

Presenting a flat-roof property for buy to let mortgage approval

While flat roofs are considered more specialist by many lenders, a well-presented application can significantly increase your chances of success. The key is to pre-empt lender concerns by showing that the roof is well-constructed, well-maintained, and insurable — and that the property as a whole presents low lending risk.

Provide detailed roof information upfront

Offer the lender or broker the following details early in the process:

• Construction type: What material is the flat roof made from? Common types include felt, EPDM (Ethylene Propylene Diene Terpolymer, which is an extremely durable synthetic rubber roofing membrane) rubber, GRP (fibreglass), or bitumen.
• Extent of the flat roof: Estimate the percentage of the roof that is flat vs. pitched. If the flat roof covers a small area (e.g. an extension), highlight this.
• Age of the roof: When was the flat roof last installed or refurbished?
• Guarantees or warranties: Does the roof come with a guarantee (e.g. 10-, 15-, or 20-year coverage)? Include a copy if available.
• Recent maintenance: If any inspections or repairs have been carried out recently, share receipts or contractor reports.

If the flat roof has been redone with a long-lasting material like GRP or EPDM, highlight this — some lenders will be more comfortable when these modern materials are used.

Commission a roofing report (if needed)

If the roof looks old, is of unknown age, or appears in poor condition, consider commissioning a roofing survey or inspection report before the valuation. This:

• Reassures the lender that you're proactive
• Can help avoid down-valuations or retentions
• May be required by the lender anyway, so getting ahead of it avoids delays

Get buildings insurance quotes in advance

Because lenders want to ensure that properties are fully insurable, provide a quote or confirmation from a reputable insurer that cover is available — with no exclusions relating to the flat roof. This is especially important if more than 25% of the roof area is flat.

Highlight the property’s investment merits

Offset the flat roof concern by clearly presenting the property's other strengths:

• Rental demand:Show that the area has strong tenant interest and consistent demand.
• Comparable rents:Provide evidence of similar properties achieving good rental yields.
• Condition: Ensure the rest of the property is well maintained and ready to let.
• Letting history (if applicable):If it’s already tenanted, highlight low voids and stable income.

This makes the property a stronger lending prospect overall.

Choose the right lender

Some lenders are more flexible with flat roofs than others. A few key considerations:

• Mainstream lenders: May have stricter criteria and be cautious if more than 25–30% of the roof is flat.
• Specialist or intermediary-only lenders:Often allow up to 100% flat roof if it’s in good condition, modern, and insurable.
• Broker-only access: Use a mortgage broker with experience in non-standard property types — they’ll know which lenders to approach and how best to package the case.

Prepare for the valuation

Before the surveyor visit:

• Clean and clear the roof area, especially if it’s visible from above or accessed via a terrace.
• Ensure gutters and downpipes are functional.
• Provide access to any parts of the property with a flat roof so the surveyor can inspect and assess easily.

A positive valuation report is key to getting the loan approved at the full purchase price or expected value.

Checklist

Final tip on flat roofs

Working with our specialist broker team takes all the work off your shoulders in terms of finding all the lenders that will accept your property, and then calculating which one offers you the best financial outcome based on your objectives.