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Our guide to Loft Conversions

A loft conversion is one of the best ways of adding extra space to your home and is often more cost effective than some of the other extension options available. Depending on the layout of your existing property, you may be able to add two bedrooms or an ensuite bedroom. As this utilises an existing space, here are some key considerations to think about before starting.

If you’d like some more advice about any of the items covered here, please feel free to get in touch!

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Is my loft suitable for a conversion?

Head height

As a minimum head height in your finished loft we recommend that you achieve 2.1m. Whilst there are no rules for what constitutes a minimum head height, a standard door is 1981mm high so you can imagine what kind of space you would have if the ceiling was any less than 2.1m!

To understand what height you can achieve take a tape measure into your loft and measure to the underside of the ridge board to the top of the ceiling joists for the first floor. It is likely that you need to upgrade these joists as they were most likely not designed for the weight of an additional storey, and if you have a ‘cold loft’ you will need to have a thick layer of insulation on top. With these factors in mind if you subtract 200mm from the measure from the underside of the ridge boards you should have an idea of what you will be working with.

If you don’t have enough room it doesn’t mean that you can’t undertake a conversion. There are clever ways to increase head height but could involve a bit more work [and therefore cost!].

The pitch

The roof pitch is the angle at which the roof is formed. A high, steep pitch will mean that you have more head height in the centre of the space, and therefore more horizontal space before you get to the eaves, making the room feel much bigger.

Structure type

The structure of your roof will depend on how old your house is. Older roofs tend to be made from timbers cut to size and assembled on site, whereas newer roofs tend to be made from roof trusses cut off-site comprising smaller sections of timber as the truss is a more efficient structure.

What this means is that in a newer roof the trusses are likely to require strengthening to take the extra weight of insulation and internal finishes that they were not originally designed to take, whereas with older roofs only modifications, like a steel ridge beam, may be required.

Speed of build and disruption to your home

A massive advantage to a loft conversion is that they are very quick to install and your builders will not need to use your front door for access during the messiest parts of the build. Erecting scaffolding front and back and then opening a hole in the front roof slope for materials is generally the way that loft conversions start. This means that the builders will be happily getting to work upstairs in the loft while you can continue downstairs as normal. As the roof work is mostly carpentry you could be looking at new roof and structure completed within 2-3 weeks! The rest of the project takes a bit longer of course to fit it out.


Although you may not be living in your loft yet, it doesn’t mean that it is not in use. If you’ve an older house then there could be water tanks in there with a range of pipework going to and fro. If this is the case then you may need to move these or upgrade your services before the structural work can start. To avoid expensive upgrades of your system we have moved these into purpose built cupboards as part of the loft layout, so it is good to plan for this early on.

Chimneys are also often found in lofts – these can be removed if defunct to give you extra important space. You’ll need an engineer to help as the external chimney will probably need to stay, especially if it is on a party wall line with your neighbour.

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Different types of loft conversion and guide for budgets

The factors above will affect the time, cost and complexity of your loft conversion. The work can have a dramatic effect on your budget, so before you start it is worth checking how much value could be added to your property to see if it is worth it. Here are some rough estimates to help you plan.

Basic Conversion - £15,000 - £25,000.

This is a ‘room in roof’ loft conversion. This is the easiest to undertake and can mostly be completed from inside. The roof is retained and you fit out from the inside, punching a few holes in it for velux style rooflights. Unless you have a steep roof pitch and a very high ridge height, this will provide you with the least useable space of the conversion types.

If you don’t already have stairs into your loft, these can be tricky to accommodate and we recommend getting some advice from an architect to help you plan these out, achieve minimum head room for your stair up from ground level and get building regulations approval.

Dormer - £25,000 - £45,000

These are very popular because they are also quite straightforward to install, but are more expensive as the back half of your roof needs to be demolished and re-built. These add a big, square elevation at the rear of the property and so internally you also get a large squared-off room which feels less like a loft.

These can be large enough for a bedroom with ensuite, or two bedrooms depending on what you are trying to achieve.

Try adding a set of double French doors and railings to create a juliette balcony to get a wow-factor and sense of space. Furnishing a loft can be tricky with the angled front slope, however we have plenty of tricks on how to create walk-in wardrobes and dressing spaces to maximise your new space.

Changing roof structure - £50,000 - £70,000

If you want a conversion but you don’t have enough existing head height beneath the ridge board to make it possible, there are still ways of making it happen.

The easiest thing to do will be to raise the ridge. This will require planning permission as does not fall within your permitted development rights, however is straightforward. This can often be done by moving the position of the existing ridge towards the back of your house and maintaining the pitch of the front roof slope to gain the extra height.

An alternative, and more expensive option, is to lower the ceiling of the first floor. This would only make sense if you live in an area with very high property values per square metre as this is the most expensive option and it won’t be possible for you to continue living upstairs while this happens. You should factor in costs for temporary accommodation [or a holiday!] so this part of the build happens when you’re not home.

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Different types of loft conversion and guide for budgets

Permitted development rights

We’re experts at advising you on different forms of planning permissions suitable for your project. In many cases you should be able to use your permitted development rights and we’ll design it so that it qualifies.

Environmentally friendly

If you want to build an environmentally friendly space, make sure you consider the different types of insulation and building materials available. Expanded foam style boards are often used and can reduce the depth of insulation needed to achieve the required energy conservation ratings [referred to as U-values]. However these are questionable in terms of creating a healthy home and so you could use recycled based products or even natural products like sheeps wool!



  • Permitted development rights

If adding a dormer you can normally do so using your permitted development rights, provided you adhere to the strict criteria set out by the government. This route can save you time and money in the design and planning phase.

kitchen extension london improvement architect design loft conversion refurbishment


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