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Buying a Flat Roof House

Martha Lott

Written by

9th Dec 2021 (Last updated on 16th Mar 2023) 6 minute read

Flat roofs are a popular type of construction for extensions due to their affordability. This means that there are a number of properties in the UK that have flat roofs on all or part of the home. However, buying a flat roof house comes 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 costly, especially if the damage is so severe enough you need to replace the entire roof.

  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. How Much Does a Flat Roof Extension Cost?
  8. 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 versatile and simple to maintain, but they can also be costly to repair. They are an energy-efficient alternative to sloped roofs but often come with 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. A 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 house, it’s essential you check the condition of the roof. The best way to assess this is through a RICS home survey. Whilst a RICS Home Survey Level 3 is the most thorough and recommended survey for a building like this, the 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 high risk by mortgage providers and insurance companies. This means that those who are willing to lend may charge higher rates.

Non-standard homes are often difficult to resell, making them an unreliable form of security for lenders. It’s 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 non-standard homes. This 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. They 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. Some of the most common problems with flat roof houses include:

1. 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 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.

2. 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.

3. 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.

4. Flashing Deteriorates

Flashing will be found around the edges of a flat roof. Over time, this can 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.

5. 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.

6. Blistering and Cracking

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

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’re 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 the repairs needed, the work itself must be conducted by a specialist.

The repair work required can be expensive. The final cost will depend 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.

Flat roofs are usually easier to install and they also provide homeowners with the option of adding a terrace or balcony. 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, making it more appealing to future buyers.

Before arranging a flat roof extension, you should consult with your solicitor. You may find issues with planning permission.

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How Much Does a Flat Roof Extension Cost?

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 June 2022.

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.

Martha Lott

Written by Martha Lott

Having guest authored for many property websites, Martha now researches and writes articles for everything moving house related, from remortgages to conveyancing costs.

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