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How to Add a Pitched Roof Extension: Ideas, Costs and Advice

Stone clad extension to cottage with large sliding doors
(Image credit: Mark Ashbee)

Adding extra space with a pitched roof extension will enable your existing home to properly function for your family and lifestyle. Pitched roofs can be adapted to suit the particular location's tradition or put a new style spin on an existing structure — be it contemporary or period-style. Plus, they look great when used during a large two-storey addition, as well as a petite extension. 

There's a lot that goes into building an extension, so having a basic grasp of the shape, size and style of your dream new space will help to create a brief for your architect at the design stage of a project. 

Take a look below as we explore the pros and cons of a pitched roof extension, what to consider in terms of materials and budget, and, of course, loads of real-project inspiration. 

What is a Pitched Roof Extension?

Simply put, a pitched roof extension is an addition to an existing house with a roof structure in the shape of a triangle. The roof design therefore enables rain, snow and ice to slide off and into the gutters. 

Pitched roofs can refer to any style of roof with a ridge or apex – pretty much anything other than flat roof extensions – although generally when they are being referred to, a classic pitch with a gable end is intended.

timber clad double height extension with zinc roof

The pitched roof of this extension mirrors the angle of the adjacent existing barn. Modern extension design ideas such as the grey zinc roof and cladding reflects the grey hues of the stone and original roof tiles.  (Image credit: Matthew Smith)

Advantages of a Pitched Roof Extension

"Pitched roof extensions offer many benefits and are quite often a popular way to extend," begins George Allen, regional design consultant from Oakwrights (opens in new tab), including: 

  • More insulation can be installed in the roof, providing better energy efficiency. 
  • Can suit contemporary and traditional house extension styles. "Pitched roofs are more traditional, but they can appear contemporary if a modern material is used and can be vaulted internally to provide drama," advises Lydia Robinson, founder of Design Storey Architects.
  • "The vaulted ceiling roof space offers an airy feeling to the room, linking a room with lower ceilings for high ridge lines and lots of light!" says George Allen. 
  • "Pitched roof extensions are also very versatile, with multiple roof material options from clay, slate, shingles and zinc, there is an aesthetic to suit any property," adds George Allen.
  • "There is also a benefit that pitched roofs can also help you overcome planning constraints," adds Yaniv Peer, director at Iguana Architects (opens in new tab). "Traditional extensions under a householder application will normally be allowed to a depth of 3.5 under the planners discretion. However, if you intend on extending further than this then you will need a little ace up your sleeve and that comes in the form of pitching the roof eaves height down to 2m at neighbours boundary. Permitted Development (PD) Rights allow you to build up a fence up to a height of 2m and as such the position made to planning officers is that there is no further impact to outlook from the neighbours side then a garden fence."
  • In a similar way to hipped roof extensions, pitched roofs are more stable than flat roofs when dealing with snow or heavy rain.

timber frame extension with exposed beams in open plan space

(Image credit: David Barbour)

Negatives of Choosing a Pitched Roof Design

However, there are some aspects in which pitched roof extension might not be suitable for every project:

  • Can cost more than a flat roof , although not always (see below for more details).
  • The design, roof slope and angle, and materials are key to a successful pitched roof extension — get any wrong and the finished product will look inappropriate to the existing house.
  • The composition of the structure means there is increased burden placed on the foundations which may impact the depth of the required footings for the extension.
  • Personal taste — flat roofs generally offer a more contemporary look which appeals to different homeowners. 
  • Some planning permission departments might prefer a completely different style of extension to that of an existing house to clearly demarcate the old and new structures
  • Can't have a green roof on a pitched extension. 

cork clad small extension with angled pitched roof

(Image credit: Chris Snook)

How Much Does a Pitched Roof Extension Cost?

"Estimating jobs like pitched roof extension in the current market has its difficulties," explains Brian Berry, Chief Executive of the Federation of Master Builders (opens in new tab) (FMB). "We are seeing material costs at all-time highs. This increase is driven by a range of issues such as inflation, export duties, the war in Ukraine and energy costs.

"This is putting immense pressure on the bottom lines of small, local builders. 98% of small builders reported higher material costs on Q1 2022, with 83% of builders putting up their prices. This rise in cost, may understandably push customers to look for cheap and quick solutions. However, I urge extreme caution when looking for quotes, a good builder is a busy builder and may not come cheap. We would recommend collecting at least 3 quotes and using a service like the FMB’s ‘Find a Builder’ tool to ensure you are getting a quality builder. 

"Consumers may also find that builders are using flexible contracts, this is to cope with the volatility of material costs, which ensures builders aren’t left out of pocket and keep jobs viable. The last thing you want half-way through a job is a builder going bust. Therefore, in the current market, you need to factor into your budget that the initial quote may end up being higher”.

For a quick estimate, use our extension cost calculator

large living room with vaulted oak frame ceiling

(Image credit: Nikhilesh Haval c/o Welsh Oak Frame)

Is a Pitched Roof Extension More Expensive Than a Flat Roof? 

"No, I believe pitched roofs and flat roofs are of a similar cost, subject to design," says a member of Federation of Master Builders. " A simple pitched roof is probably cheaper.  A more complex one would likely be more expensive.  An added benefit of a pitched roof is that you may be able to have a vaulted ceiling (one that follows the profile of the roof above rather than being flat) to add interest to the space."

"Technically there is more consideration that needs to be given by the contractor to the works and as such it demands a contractor with good carpentry skills," explains Iguana Architects' Yaniv Peer. "You must also balance out the type of glazing you intend on using i.e. is it to follow the form of the geometry or will you keep it rectilinear for the sake of costs? The same logic and also apply when considering external cladding on a angled facades, it is easier for external bricks to be applied to a flat surface then to cut bricks to an angle." 

"Pitched roof extensions can turn out to be a cheaper alternative," says Oakwrights' George Allen. "This is primarily due to the cost of tiling compared to flat roof membrane roofing and the lantern cost.

"Tiling is also a much more common building practice, therefore not carrying as much of a premium. The wall space available on the existing exterior can govern your ridge height. If first floor windows are at a low level then a flat roof with lantern may be the best option."

"Pitched garden rooms can be in the similar region cost wise, however most clients go for a flat roof with lantern if they don’t have the height from ground to first floor for the pitched roof. So it is more of a personal preference or for practical reasons than cost," adds Oakrights' regional design consultant Zoe Grey. 

small side extension to cottage with timber cladding

(Image credit: Nikhilesh Haval c/o Welsh Oak Frame)

Can you Add a Pitched Roof to an Existing Extension?

"Changing a flat roof to a pitched roof shouldn't change the structural loading on the existing extension foundations (but this should be confirmed by construction professions)" says FMB.

"This is subject to the detail of the host building, local planning constraints and structural survey." 

Pitched Roof Extensions: 5 Inspiring Ideas

1. Get Pitched Roof Angels and Proportions Right

stone clad pitched roof extension to traditional cottage with outside patio

(Image credit: C/o Design Decoded)

"When designing a pitched roof it is important to consider the angle of the pitch — if you use the same angle as the existing building it will help the extension to feel like it marries in," says Lydia Robinson.

"The ratio of roof to wall is another important design factor to keep in mind. In areas such as the Cotswolds, low walls are often paired with steeply pitched roofs, making the latter very dominant. This characteristic of the local architecture is often overlooked in the proportions of extensions."

2. Choose a Low Pitched Roof Extension

living room extension with low pitched vaulted ceiling

(Image credit: David Barbour)

If you're wanting a pitched roof, but don't want to disturb the views from the first floor rooms, a low pitch is a good small house extension idea

The angle of this living room's ceiling provides the illusion of a grand vaulted ceiling extension, but in reality the slope doesn't register as dramatic when viewed from the exterior. 

3. Celebrate A Pitched Roof Extension with a Vaulted Ceiling

oak frame double storey extension with pitched roof

(Image credit: Richard Kiely c/o Oakwrights)

When adding floorspace to their bungalow, the owners of this house chose to add an oak frame extension with a dramatic vaulted ceiling. 

The design of the double-storey extension mimics the similar pitch of the original dormer bungalow and provides a characterful mezzanine master bedroom space. 

4. Add an Extension With a Double Pitched Roof

double pitched roof on single storey extension with view to kitchen

(Image credit: Juliet Murphy)

"Once key aspects of Biophilic design is connection to the nature/natures systems and in particular to natural light," explains Yaniv Peer, who designed this semi detached house extension

"Given that the property was north facing we carried out a daylight modelling exercise and the final 3D model that let the most amount of light was the butterfly roof structure. It allows light during morning family breakfast and the evening dinners." 

5. Use Glass for a Conservatory-style Pitched Extension

glass pitched roof extension with large kitchen diner

(Image credit: IQ Glass)

Debating between an extension or conservatory? A pitched roof glass extension has given this house the best of both worlds. 

Pitched garden rooms are a popular way of connecting with the garden, but this elegant kitchen extension really shows how you can be make a functional space that can be used come rain or shine. 

Assistant Editor Amy began working for Homebuilding & Renovating in 2018. She has an interest in sustainable building methods and always has her eye on the latest design ideas. Amy has interviewed countless self builders, renovators and extenders about their experiences for Homebuilding & Renovating magazine. She is currently renovating a mid-century home, together with her partner, on a DIY basis, and has recently fitted her own kitchen.