The cost of a loft conversion can be anywhere between £55k and £70k. More ambitious projects with unique structural challenges and bespoke design briefs can cost more. To give you a better idea of the costs involved with converting your loft, we’ve put together this short guide. It provides a rundown of the factors influencing the final price of a conversion and why you should consider transforming your loft in the first place.

Why build a loft conversion?

Lofts are often underutilized spaces, meaning that they don’t always offer homeowners the most value. The space they occupy, however, is incredibly useful. Lofts can be transformed from redundant, dusty areas into new rooms for your property. Imagine a roof-top bathroom fitted with wall-to-wall feature windows, offering expansive vistas of your local area whilst remaining hidden. Or perhaps a well-designed study room, cocooned from the hustle and bustle of the rest of the house. Whatever your wants and needs, loft conversions offer a space to fulfil them.

Loft conversion cost factors


Size is a significant factor in the cost of your loft conversion. This is determined both by your property type and your designs. Whilst most loft conversions fully utilise all available space, others are more modest, and only take up a portion of the loft space. Whether you opt for a bijou bedroom conversion or a full-scale studio fit-out, however, a loft conversion will give more living space. 

Loft type

There are several different types of loft extension, with each one more or less suitable for a particular shape and style of property. What works for a modern semi-detached house might not be suitable for a Victorian terraced property. Here are the main types of loft extension we offer at Plus Rooms and what kind of properties they can be used with.  

Dormer Loft Conversion

A dormer is a structure that’s added to a roof in order to increase the amount of usable floor space in a loft space, whilst allowing for extra headroom. It’s a common option for loft extension; it can be used with any properties that have a pitched roof. 

  • White Hard Ln (SW13) – This conversion created a large master bedroom and ensuite over the mainframe and rear of the property, substantially increasing the floorspace of the property.
  • Fawnsbrake Ave (SE24) – An L-shaped loft conversion with dormer structures over the mainframe and rear of the property. Highlights of this bold project include feature windows and an open-plan bedroom/en-suite.

Hip-to-gable loft conversion

Many properties (especially end-of-terrace houses) have a ‘hipped’ roof. This type of roof has three sides which slope to a central point, limiting the amount of usable floor space within a loft area.

A hip-to-gable loft conversion works by replacing one of the sloping sides of a hipped roof with a vertical wall. This creates a four-sided roof and provides more space within the loft area. When combined with a dormer, it can significantly increase the amount of size available for a conversion.    

  • Mostyn Rd (SW19) – This project uses a hip-to-gable dormer to create a large, bright master bedroom and ensuite that looks out over the local area. 
  • Lime Grove (TW1) – This conversion transformed a bungalow into a spacious family home, creating two bedrooms and a shared bathroom.

Mansard loft conversion

Mansard loft conversions require the restructuring of the roof. They work by flattening the top of the roof to create a more angular slope which usually sits at the rear of the property. Similarly to dormers, this increases the amount of headspace in the loft area and ensures that it receives the most amount of natural light as possible.

In terms of viable properties, mansard loft conversions can work with all types, from bungalows to detached, semi-detached, and terraced houses.

  • Rush Hill Rd (SW11) – A front and rear mansard has been used to convert this roof into a new floor containing a guest bedroom, en-suite, and cinema room.
  • Devereux Road (SW11) – A full rear mansard has been extended across the full width of this Victorian terrace property to accommodate two spacious double bedrooms.

Let us talk you through the options

Given that there are so many factors in the cost of a loft conversion, we’d always advise speaking to a qualified contractor to get an accurate quote. At Plus Rooms, we take pride in offering clients a gold-standard loft extension service, from quoting through to design concepts and construction. If you’d like to know more about our work, take a look at our past projects or feel free to get in contact – we’re here to help.