Should You Buy A House With A Flat Roof? (Flat Roof Pros and Cons)

Should you buy a house with a flat roof

Have you been looking for months to find the perfect next home and found a house with a flat roof or with a flat roof extension. Houses with flat roofs are not liked by everyone, which is why it’s important to know whether you should buy a house with a flat roof.

Before you buy a house with a flat roof make sure you pay for a full building survey to check the integrity of the structure and state of repair of the membrane covering. Flat roof repairs can be costly, which means if you don’t get this checked before you buy it could cost you in the future.

Houses with flat roofs problems

Houses with flat roofs problems

If you are considering to buy a house with a flat roof you should think about the problems houses with flat roofs have. The top flat roofs problems include:

Flat roofs leak

Flat roofs are notorious for leaking, which is why they have such a bad reputation. The reason flat roofs develop leaks is because they are flat. When water collects on the flat surface it can only go one way. This is down through the roof and into the room below.

Water leaks can be prevented by installing a new modern flat roof system (see below), rather than the old style asphalt or felt roofs.

Let me share a funny experience of a house I purchased with a flat roof. Soon after I purchased the house with a flat roof I recall getting home to find I had a new waterfall inside the house. There was water cascading down the stairs. A large hole had opened up in the flat roof above the entrance hall.

In the pouring rain I had to get on the roof to patch the hole up. I did this with what I had. This happened to be planks of wood and bin bags to limit the water flow. All worked out in the end. I obtained planning permission to build a pitched roof over the flat roof section of the house.

Pooling of water

A common problem with flat roofs is that over time the roof settles. This settling can create dips in the flat roof surface. When it rains or when snow melts these dips cause a pooling effect of water.

Water is heavy and over time if these dips are not repaired this could lead to leaks and water penetration.

Alligatoring or Crocodiling

Crocodile cracking or alligatored asphalt is used to describe the pattern formed in old asphalt. The alligatoring is caused by the loss of flexibility to the material and in time the asphalt will split and leak to the room below.

If you see this type of cracking on a flat roof it’s time for it to be replaced.

Flashing deteriorates

Over time the flashing around the edges of the flat roof can crack or pull away from the roof itself. This will lead to water leaks and will need to be repaired or the whole flat roof replaced.

Growing vegetation and weeds

Flat roofs are notorious for the growth of vegetation like weeds and mosses. Any vegetation on a flat roof needs to be removed, otherwise the roots of the plants could damage the flat roof membrane and cause leaks.


Over time the sun can cause the asphalt to blister. Blistering on a flat roof is a sure sign the flat roof needs replacing.

Incorrect roof angle

Flat roofs shouldn’t be completely flat. There should be a slight angle or fall for rain water to run-off to the guttering and drainage. If there’s not enough flat roof angle this will cause water pooling and will eventually lead to roof leaks.

Build-up of snow

If you live in an area prone to snow this can collect on top of a flat roof. A thick layer of snow is heavy and may cause unnecessary stress to the flat roof structure.

But the other problem comes when the snow thaws. This can cause a flood of water into the property. You may like to read this story about a house with a flat roof which flooded after the snow thawed.

Can you get a mortgage on a house with a flat roof

Can you get a mortgage on a house with a flat roof?

You can get a mortgage on a house with a flat roof, but some lenders include terms that place limits on the total area of the house that can be flat. A flat roof is considered non-standard construction which may make the house more difficult to sell if it were to be repossessed in the future.

If the house has a 100% flat roof not as many mortgage lenders will lend on this type of flat roof house, as some mortgage lenders don’t like 100% flat roofs.

The lender may also require a flat roof survey before lending to confirm the flat roof is in good repair. You might be better to arrange a mortgage using a mortgage broker who will match the property with the right lender.

A full building survey by a suitably qualified surveyor will determine the overall condition of the flat roof. The surveyor should be able to assess the condition of the covering and estimate remaining life of the flat roof.

If the flat roof is in need of repair or needs to be replaced, you should ask the vendor of the property to reduce the asking price accordingly. Unless the asking price already reflects the state of repair of the flat roof.

If the flat roof needs repairing, the mortgage lender may put a retention on the mortgage until the roof has been repaired. If you are still keen to buy this house with a flat roof in need of repair, but with a mortgage retention, you should read this article about doing building works between exchange and completion.

Can you get insurance on a house with a flat roof

Can you get insurance on a house with a flat roof?

Yes you can insure a house with a flat roof, but flat roofs are considered a higher risk as they tend to be more prone to weather damage and leaks. Choose your insurance company carefully, as some charge excessively for flat roofs. Also, some insurers will simply refuse to insure flat roof properties.

But if you go ahead and buy the house with a flat roof, you must disclose the flat roof when you insure. They will need to know the percentage of flat roof covering of the house. This may be 100% flat roof or a flat roof over an extension or only a part of the house.

Ask your building surveyor to calculate the flat roof percentage in preparation for insuring the property after you exchange of contracts.

Another concern for insurance companies is that flat roofs offer easier access to criminals. This is another reason why insurance on houses with flat roofs tend to be more expensive than on houses of traditional construction.

Is it more difficult to sell a house with a flat roof

Is it more difficult to sell a house with a flat roof?

Houses with flat roofs are more difficult to sell than houses with traditional pitched roofs because most people prefer the look of the traditional design.

But also, houses with flat roofs can be more tricky to get a mortgage or more expensive to insure. However, this will depend on the total area of the house that is flat.

For example, if the house has a flat roof extension this should not make it difficult to sell, unless the flat roof is in need of repair.

With all else staying the same, houses with flat roofs tend to be cheaper to buy than houses with traditional pitched roofs. Which means you may be able to grab yourself a bargain.

But remember the resale value. You don’t want to end up having problems selling your house in the future.

Flat roof house pros and cons

Flat roof house pros and cons

There are pros and cons of houses with flat roofs.

Pros of a house with a flat roof

  1. Houses with flat roofs or with extensions with a flat roof tend to be cheaper to construct than traditional pitched roofs.
  2. Flat roofs are quicker and easier to construct.
  3. Flat roofs tend to be easier to access and clean.
  4. Extensions with flat roofs are cheaper to build.
  5. The flat roof of an extension can be used as a balcony, as long as the roof has been constructed accordingly.
  6. You can put really great roof lanterns in flat roofs for extra light in the room below.

Cons of a house with a flat roof

  1. Flat roofs often have drainage problems when compared to traditional pitched roofs.
  2. Flat roofs tend not to last as long as traditional pitched roofs. But this is changing with modern materials, which is making flat roofs last much longer.
  3. Over time flat roofs tend to cause more problems and will be more expensive to maintain.
  4. Houses with flat roofs often require more maintenance to keep them watertight.
  5. Flat roofs need to be inspected at least once a year or better still twice annually.
  6. Houses with old flat roofs tend to be badly insulated leading to greater heat loss in the winter and over-heating in the summer.
What is the life expectancy of a flat roof

What is the life expectancy of a flat roof?

A typical flat roof membrane should last on average between 20 to 25 years before it needs to be replaced. But old style flat roofs made from asphalt may need replacing with in 10 years.

However, if you replace your flat roof with a rubber membrane this may last over 50 years.

Modern flat roof membrane materials are available that last much longer and include:

  • Rubber Roofing Systems (ethylene propylene diene monomer) can have a 50-year lifespan. Rubber flat roofs are flexible and will expand and contract with the weather. They don’t blister or crack.
  • A Built Up Flat Roof (BUR) with layers of molten tar and gravel offer a 10 to 20 year lifespan. But the installation is messy and the covering is heavy, so the structure may need to be reinforced. They also tend to be expensive to install.
  • Special resin coverings made from Glass Reinforced Polyester (GRP) instead of the traditional felt-type can last at least 30 years. Fibre glass roofs are durable and offer good weatherproofing and are lightweight, but can be noisy in the rain.
  • PVC flat roofs offer a 20-year lifespan and are strong and durable. The additives in the PVC to make it flexible can break down and pose problems after 20 years. PVC flat roofs can also be noisy in the rain.
Buying A House With A Flat Roof Extension

Buying a house with a flat roof extension

If the house you’re buying has a flat roof extension, rather than 100% flat roof, you should still have the roof surveyed to check its state of repair. Your solicitor should be checking the correct planning permissions were applied for and whether the flat roof has a transferable warranty.

Flat roofs are used on extensions usually because they are cheaper to construct. If the flat roof on the house you’re considering to buy has an old style covering, this shouldn’t put you off buying, so long as your offer reflects the state of repair and estimated remaining life span.

But on the other hand modern flat roofs are constructed of materials that have a longer life span, which should mean the flat roof won’t need replacing or require any repair work doing.

Buying a house with a flat roof extension - Glass roof lantern
Glass Roof Lantern for flat roof extension – image courtesy of ATT Fabrications

Also, if the flat roof extension doesn’t already have a glass roof lantern, you should consider installing one of these. As per the above image.

For flat roof extensions you will still need to notify your insurance company about the flat roof. They will want to know what area is covered by the extension as a percentage of the total house.

Final thoughts on buying a house with a flat roof

Before you buy a property with a flat roof make sure you have the condition of the roof checked by a surveyor. Otherwise this may cost you a lot of money down the road when you discover the flat roof is leaking.

If a problem is discovered with the flat roof before you buy the property this may help your decision about whether you should buy a house with a flat roof. But it may also help you to negotiate a reduction in the asking price should you decide to proceed.

Look into whether it’s possible to replace the flat roof with a standard pitched roof instead. You may be able to do this without planning permission, but you need to check how much it will cost.

You need to check how a pitched roof will impact on the rest of the house if it’s not 100% flat. Or how it will impact on the surrounding houses, especially if the house is not detached.

I hope you’ve enjoyed this article about should you buy a house with a flat roof

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Should You Buy A House With A Flat Roof? (Flat Roof Pros and Cons)

Article written by Russell Bowyer who has been investing in property since purchasing his first commercial property in the 1990's for his own Chartered Accountancy business. But his first property investment project was to turn an old dilapidated restaurant into a large 5-bed home, which he purchased for £117,500 and sold for £450,000 (to see an "after" photo of the house before it was sold see here: About). Russell owns a number of investment properties, which includes houses, flats and HMO's. More recently he has turned his creative side to investing in property using lease options. His largest lease option deal to date was to acquire 12 properties worth over £2 million for just £12, which means he paid just £1 to acquire each property!

2 thoughts on “Should You Buy A House With A Flat Roof? (Flat Roof Pros and Cons)

  1. An interesting read. Thank you.
    I have just looked at a 1953 council house, it has a flat roof extention at the back and a flat roof large garage to the side 1985.
    There are already 4 offers on the table . . No time to have a friend to look at. . Therefore going to be dependent on the survey, if I am successful in having my offer accepted!

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