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Buying a Flat Roof House

Zenyx Griffiths

Written by

9th Dec 2021 (Last updated on 14th Dec 2021) 6 minute read

There are a number of properties in the UK that have flat roofs on all or just part of the home. Flat roofs are also a popular type of construction for extensions due to their affordability. However, flat roof houses come with a range of problems that you’ll need to consider.

If you’re buying a flat roof house, it’s vital you arrange a homebuyers survey (Level 2 Home Survey) or building survey (Level 3 Home Survey) to uncover any obvious issues. Repairing a flat roof home can be a costly experience, especially if the damage is severe enough that you need to replace the entire roof.

Compare My Move’s professional team work alongside a number of property and finance experts to create insightful guides that will aid our users through the moving process. In this article, we explore the issues that come with buying a flat roof house and why buyers should arrange a home survey before continuing with the sale.

This article will cover the following:
  1. What is a Flat Roof House?
  2. Can You Get a Mortgage on a Flat Roof House?
  3. Problems With Flat Roof Houses
  4. How Can A Property Survey Help?
  5. Pros and Cons of Buying a Flat Roof House
  6. What is a Flat Roof Extension?
  7. Explore our Next Guide

What is a Flat Roof House?

As the name suggests, a flat roof house is a non-standard property that does not have the typical pitched roof. Flat roofs are considered as versatile and simple to maintain, but they can also be costly to repair. They are an energy-efficient alternative to sloped roofs but they often come with several issues such as a higher risk of leaking and water pooling.

Flat roofs often have a shorter lifespan compared to sloped roofs. A standard flat roof membrane will likely last around 20-25 years before it needs to be replaced whilst the stronger rubber membrane can last up to 50 years. However, if the property has an older style such as an asphalt flat roof, then it will need to be replaced much earlier - often 10 years.

Before purchasing a flat roof property, it’s essential you check the condition of the roof as repair work can be costly. The best way to assess the property is through a RICS home survey. Whilst a building survey or RICS Home Survey Level 3 is the most thorough and recommended survey for a building like this, a homebuyers report or RICS Home Survey Level 3 will also suffice.

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Can You Get a Mortgage on a Flat Roof House?

As flat roof houses are considered non-standard properties, it can be difficult to secure a mortgage for them. They are considered as high risk by mortgage providers and insurance companies, meaning those who are willing to lend on this type of home may charge higher rates.

Non-standard homes are often difficult to resell, making them an unreliable form of security for lenders. It is possible to secure a mortgage on a flat roof property, but it’s recommended you speak to a mortgage broker for the right advice first.

There will only be a few lenders who will consider a mortgage on this type of non-standard home, which is why it’s recommended you speak to a professional to point you in the right direction. Those who do offer loans will likely stipulate that the loan is subject to the property’s valuation and may require a larger deposit.

Problems With Flat Roof Houses

When organising a property survey, know that both the RICS Home Survey Level 2 and Level 3 reports should highlight any obvious issues or damage done to the property. Some of the most common problems with flat roof houses include:

Potential Leaks

One of the biggest problems with flat roof houses is the risk of leaks. When water collects on a flat roof, it can easily develop leaks as there’s only one place for the water to go: down and into the room below.

It is possible to prevent water leaks by installing a modern flat roof system, however, it is not a guarantee.

Pooling of Water

As a flat roof settles over time, it can create areas with enough of a dip that water begins to pool on the surface. These dips can collect rain or even snow, increasing the risk of leaks and water penetration.

Build-Up of Snow

As mentioned above, flat roofs can cause a build-up of snow. A heavy, thick layer of snow can cause unnecessary stress to the roof and weaken it. Once the snow thaws, the property is then at risk of flooding.

Flashing Deteriorates

Around the edges of a flat roof will be flashing. Over time, this can slowly deteriorate and pull away from the property. This will again increase the risk of leaks and can be costly to repair. If there is significant damage, the entire roof may need to be replaced.

Incorrect Roof Angle

Despite the name, flat roofs should not be constructed completely flat. There must be a slight angle for rainwater to run into the guttering. If this was done incorrectly, your roof will be more susceptible to water pooling and leaks.

Blistering and Cracking

Flat roofs are often built using asphalt - this material is prone to blistering from exposure to the sun over time. If the flat roof house you’re viewing shows signs of blistering, it may be a sign that the roof needs replacing completely.

Flat roofs are also prone to ‘crocodile cracking’ and ‘alligatoring’. These terms are used to describe the pattern created in old asphalt. Alligatored asphalt will lose its flexibility and the material will slowly split, causing leaks. Again, if there’s evidence of these cracks in your home survey, you may need to consider replacing the roof.

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How Can A Property Survey Help?

A homebuyers report or building survey should highlight any problems with your flat roof house. Whilst they are typically cheaper to construct, they have a shorter lifespan so it’s important they’re regularly inspected.

The home survey should uncover any signs of damage or wear to the roof, such as cracking, water pooling or leaks. Whilst your surveyor can advise you on what repairs should be considered, the work itself must be conducted by a specialist.

The repair work required can often be expensive, with the final cost depending on your location, the materials used and the size of the area affected. To replace the flat roof, you could be looking at a starting price of £1,200 or higher.

Pros and Cons of Buying a Flat Roof House


Lower construction costs.

Requires more maintenance.

Shorter construction period.

Flat roof drainage isn’t as effective.

They are very versatile and can be used as rooftop gardens.

They typically have shorter life spans.


Higher repair costs.

Easier to access and simple to clean.

Unreliable in cold weather.

Debris can easily build up.

Must be inspected at least once a year.

What is a Flat Roof Extension?

A flat roof extension is exactly what the name suggests. It can be a great way to extend your home and provide a little extra living space. Flat roof extensions are typically cheaper than other roof systems, making them a popular choice amongst homeowners.

Flat roofs are usually easier to install than pitched roofs and they also provide homeowners with the option of adding a terrace or balcony above the extension. Due to its affordability and the promise of extra space, a flat roof extension is often a great alternative to upsizing to a bigger home. Many people also believe that a flat roof extension can add value to your home, making it more appealing to future buyers should you wish to sell.

Before arranging a flat roof extension, you should consult with your solicitor to discover any issues with planning permission. To help you compare prices and options, we’ve included the average cost of different extension types below:

Type of ExtensionAverage Cost Calculated

Flat roof extension cost


Flat roof extension cost per m2


Pitched roof extension cost


Cost to convert a flat roof to a pitched roof


The data presented in the table above was taken from the CheckATrade website, correct as of December 2021.

Explore our Next Guide

This completes our surveying guide, but we have many more informative and helpful guides. To learn more read our guide to house removals.

Zenyx Griffiths

Before Compare My Move, Zenyx once wrote lifestyle and entertainment articles for the online magazine, Society19 as well as news articles for Ffotogallery.