The Cost of Converting a Flat Roof to a Pitched Roof

A roof is a major part of any home. If you have decided to convert your flat roof to a pitched roof, use this guide to understand what you can expect from your flat roof conversion.

pitched roof conversion

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What does a flat roof conversion involve?

Whether you love them or hate them, flat roofs have a reputation. Like many strong design features, on a day-to-day basis, the construction of a flat roof can prove impractical. Despite appearing to be a straight forward structure, a flat roof needs careful attention to ensure that water is able to disperse effectively.

In the UK, any design feature that faces an ongoing battle to rid itself of water, is going to need a lot of maintenance long-term. In addition, if flat roofs are not fitted with expert precision you will come across ongoing problems.

Once you begin to face issues related to: leakage, cracks, water damage, the renewal of waterproof coatings and problems in other parts of the roof caused by the presence of moisture – it is then, that you are likely to seek to replace your flat roof. Once you encounter that kind of hassle, switching to a practical, long-lasting, versatile and reliable pitched roof is going to appeal.

But what does a flat roof conversion entail?

So what should you expect when planning to carry out your flat roof conversion?

The most popular type of flat roof conversion, when switching to a pitched roof, is a trussed roof conversion. This is where a complex structured framework of angled beams, is constructed above your flat roof to bridge the gap and support your new pitched roof.

Shallow pitched roofs are favoured by most homeowners because they tend to have a higher rate of approval when it comes to seeking planning permission. Additionally, a less complex structure will inevitably cost less money and be completed quicker.

Making changes to a roof is a major structural change, so you will need to have your designs drawn up by a qualified engineer or architect. Your tradesman may be able to arrange this for you. Additionally, this is an architectural change so you will be required to obtain planning permission from your local council, before any work is carried out. There will also be specific building regulations that must be followed.

Once work begins, the next set of costs will come from the installation of your roof, including the removal of your previous roofing materials. This is a serious task that takes time and expertise. Further expense will come from the type of materials that you choose to use in the creation of your pitched roof.

In addition to the main structure, there are other things that can be done as part of your flat roof conversion, such as adding extra features like gables, creating new angles, choosing more complex trusses or even a new dormer loft window as part of a new loft conversion. However, these customisations will of course, come at a cost and need to be approved at the planning stage.

You may also find that there is additional work needed in other places, such as supplementary ceiling work due to changes made to ceiling joists or the replacement of damaged parts of the original roof structure. If you have a chimney, you will probably find that you also need to have the chimney, heating system vents and pipes extended as part of the conversion. However this could be an ideal time to have your chimney stack removed along with the roofing work. Finally, you may decide to re-do the siding so that it is in keeping with the rest of the cladding on your building.

Once again, all structural changes must be approved from the outset, to ensure that the plans are structurally sound.

A roof conversion is a structural change that affects the very architecture of your home. Therefore, this is not a job that you can do yourself. A conversion cannot be carried out by anyone other than the appropriate, approved tradesmen and professionals. Further, all planning and building regulations and procedures must be followed, in the correct order.

It is worth spending some time to calculate the height of the roof’s pitch accurately, because the higher the roof’s pitch, the more pressure it places on the walls of your home, meaning that your plans are less likely to be approved. Having to draw up and submit plans again is something that you will want to avoid because as well as delaying the project, you will also incur additional costs.

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How much does it cost to convert a flat roof to a pitched roof?

The average cost of converting a flat roof to a pitched roof is around £3600 - £4500, dependant on the types of materials used during construction, whether or not scaffolding will be used and the size of the roof.

This is a major structural job that requires a number of roofers, who usually work at a cost of around £200 – £300 per day.

Below are some estimated costs of hiring a professional roofer to convert a flat roof to a pitched roof:

Job Description Avg. Cost Duration
Smaller Roof with an open gable £3000-£3600 3-5 days
Roof with a box gable £3500-£4200 4-7 days
Large Roof with Gable with Scaffolding £4000-£4500 6-10 days

Cost Breakdown

Individual costs of converting a flat roof to a pitched roof with gable - Total Cost: £4000






Waste Removal


The sloped design of a pitched roof means that it has good drainage and is robust, weather-resistant and long-lasting. It does not need careful maintenance and is not liable to tears, leaks and cracks. Although it is more expensive to install and has a more traditional aesthetic, it is the most common style of roofing in the UK, where it is crucial that roofing can withstand strong and severe weather. Additionally, it is an energy-efficient and versatile design that can also be used as additional living space.
Yes, this is a major structural change that is higher than your existing roof, so you are obligated to seek planning permission from your local council before you begin any work. There are many different types of regulations, according to the nature of your works and the type of building that you live in. In addition, you will also need to comply with certain building regulations and standards. So ensure that you do your research thoroughly, before you embark on any works. You may find that you have to adjust your original plans to comply with council restrictions, in order for your application to be approved and work to go ahead.
Pitched roofs are robust, long—lasting and free from drainage problems. Like anything, over a long period of time, there will be some minor repairs needed from time to time, but these are small tasks that can be done in isolation. Repairs needed may include: slipped tiles, blocked valleys, missing mortar from verges or a chimney, moss on the roof or damaged guttering. However, these would be lifetime repairs that rarely occur.
Yes and no. Initially a flat roof is cheaper and simpler to install. However, in the long run, you may end up wishing that you had gone for a pitched roof which will be much easier to maintain. Over time, flat roofs will need increasing levels of maintenance because they are prone to damage, leaks, tears, problems from ill-fitting coverings, costs from replacement coverings and more.