A piggyback loft conversion raises the ridge height and extends the external walls to create a full-height loft with much more usable space. A great option for homes with low rooflines, including 1930s houses and post-war semis, where a standard dormer or hip to gable will not provide enough headroom.
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A piggyback loft conversion involves removing the existing roof, raising the external walls by around 1.3 metres and building a new, higher roof structure on top creating a full-height loft across the entire floor. This gives you far more headroom and usable space than a dormer or a Velux-only design.
Piggyback conversions work well for homes with low ridge heights where standard loft conversion methods cannot provide enough standing space. They allow you to unlock the full potential of your loft while maintaining a flexible layout and a comfortable ceiling height.
A piggyback loft conversion is one of the most expensive types of loft work because it involves lifting the entire roof, raising the external walls and building a new roof structure.
In 2025, most projects fall between £50,000 and £80,000, depending on the size of your home, the finish you choose and your location. Homes in London and the South East often sit toward the higher end of the range.
Below is a clear breakdown of the typical cost components involved in a roof lift loft conversion.
Estimated total cost: £59,950 (including contingency)
Ready to transform your loft with a stunning loft conversion?
A piggyback loft conversion delivers some of the biggest space gains of any loft type. Here are the key benefits for you as home owner.
A piggyback loft conversion has major advantages, but the following points are important to consider before starting.
As we mentioned above, there are plenty of reasons to consider a piggyback loft. By considering one, you will create a larger, practical living space with ample headroom and multiple rooms, enhancing overall functionality.
Boost your property's value and attract buyers. Customise the space to meet your needs, improve natural light with skylights and larger windows, and enhance energy efficiency. It's a cost-effective, less disruptive alternative to moving house. Make use of underutilised attic space without expanding your home's footprint.
A piggyback loft conversion is one of the most structurally significant types of loft work. Because it raises the roof height and alters the property's external appearance, it requires full planning permission in almost all cases.
Understanding the planning process, what councils look for and how building regulations apply will help you avoid delays and ensure your project is approved the first time. Below is an in-depth guide to everything you need to know before starting a roof lift loft conversion.
Most loft conversions fall under permitted development, but piggyback conversions are different. Planning permission is required because of the work:
Permitted development rules specifically state that the highest part of the roof cannot be altered without planning consent. A piggyback conversion does exactly that, so a full planning application is unavoidable. Only very isolated properties in rural areas occasionally gain approval without full planning, but these cases are rare.
Every piggyback loft conversion must comply with all Building Regulations. These rules ensure the new structure is safe, stable, energy efficient and suitable for use as a habitable room.
Because a piggyback conversion alters the entire roof and supporting walls, building control will monitor the project from structural design through to final sign-off.
Below are the core areas your builder and structural engineer must satisfy.
A piggyback loft conversion is one of the more involved loft types, and timelines vary based on the size of your home, the structural work required and the builder’s schedule. Most projects take 8 to 12 weeks once construction begins, although planning and design work happens before this.
Here is what to expect at each stage.
Most piggyback loft conversions stay within the 8 to 12 week window, but it is sensible to allow extra time for weather delays and planning approvals. Good preparation and clear communication with your builder help keep the project on schedule.
A piggyback loft conversion is one of the highest-value upgrades you can make to a home because it creates full-height, fully usable living space across the entire loft footprint. This type of conversion often adds 10 to 25 percent to a property’s market value, depending on location, size and layout.
Buyers place a premium on homes with:
Because a piggyback conversion raises the roof, the new space often feels more like a regular first-floor extension than a typical loft. Estate agents value this highly because it:
In high-demand areas such as London and the South East, a well-designed, full-height loft can add £50,000 to £150,000 or more to the resale price, often exceeding the build cost.
A piggyback loft conversion is considered a premium upgrade with strong buyer appeal, making your home more competitive on the market and delivering a strong return on investment.
