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When it comes to making home improvements, the most cost-effective options – those that add the most value for the lowest price – tend to involve increasing your available floor space. For this reason, many homeowners choose to convert their loft, maximising space that was previously used for storage (or entirely unused) into an additional bedroom.

But how much value does a loft conversion add? Is it worth the effort? And if you’re aiming to bolster your property’s potential sale price, would you be better served taking the time and likely inconvenience of converting your loft, or simply selling your house now? Read our in-depth guide to help make your mind up.

How much value could a loft conversion add to your house?

The added value of your loft conversion will depend on several factors. Every house has a price ceiling (the maximum amount that it can realistically sell for given the location and type of property). For instance, if you own a three-bedroom house worth £300,000 and the maximum price for a four-bedroom home in your area stands at £320,000, you’ll probably see little or no increase in value for adding anything other than the most basic of loft conversions. Likewise, if you currently only have two bedrooms while most other houses in your area have three or more, a loft conversion could be essential to make your property more appealing to potential buyers.

Several studies have been conducted to answer the question “does a loft conversion add value?”. According to Nationwide, a loft conversion incorporating a double bedroom and bathroom can add around 20% to the value of a three-bedroom, one-bathroom house. With the average UK house price standing at £231,185 in January 2020, this represents an average increase in value of more than £46,000.

 Focusing specifically on properties in London, a study from Abbey Lofts concluded that adding a loft conversion to a two-bedroom house in the capital could add 24.5% to its value. According to the latest London Assembly figures, the average house price in the city is £476,200 – based on these studies this would equate to more than £116,000 in increased value.

Taking a different approach, online architectural platform Resi analysed the value added by a loft conversion in different regions of England and Wales. The increases ranged from £38,328 in the North-East to £199,752 in central London (using data from July 2018).

How much does a loft conversion cost?

As with any home improvement, the cost of a loft conversion depends on various factors, including:

  •  Roof structure (explained further below)
  • Type of house (terraced, detached or semi-detached)
  • Type of conversion (e.g. are you installing dormer windows?)
  • The amount of existing available space
  • Alterations required on the floor below to accommodate a staircase
  • Location (costs will almost always be higher the closer you live to London)

 According to PriceYourJob, the average total cost of converting your loft into a bedroom with roof windows ranges from £12,500 to £20,000. Adding an ensuite bathroom as well increases the price range to £17,500-£25,000. Expect to pay between £25,000 and £30,000 for a bedroom with both dormer and roof windows, as well as an ensuite.

 These prices could be as much as £15,000 higher if your house is in the London area. You’ll also pay significantly more if your house requires significant structural work to accommodate the conversion, such as raising the roof or lowering the ceiling of the floor below. We recommend getting three quotes before choosing a construction company to carry out the work.

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Is your loft suitable for conversion?

First off, it’s important to bear in mind that some loft spaces simply aren’t suitable for converting into an extra bedroom. There are several factors that dictate whether or not a conversion is feasible (or at least cost-effective), including:

Roof height

The usable part of the loft (i.e. the distance between the bottom of the ridge timber and the top of the ceiling joist) should be at least 2.2 metres tall in order to give you sufficient headroom. There are minimum bedroom size regulations, but while there is no legally enforced minimum height limit for habitable space, you’ll realistically want at least 1.8 metres to create a liveable and attractive bedroom, be aware that there is a minimum headroom standard of 2 metres for stairways and landing – see The Building Regulations 2010: approved document K – for more information.

Roof pitch

Roofs with higher pitch angles tend to afford greater central head height, making them most suitable for a loft conversion.

Where to place your water tank

Transforming your loft into a bedroom may leave you without space for your water tank and plumbing, in which case they may need replacing with a closed system. Unvented hot water cylinders tend to be the best option – but be aware that they take up a cupboard-sized space, which you’ll need to make room for elsewhere in your house.

Type of roof structure

The vast majority of UK homes will feature one of two different roof constructions – either traditional framed or truss sectioned. The type of roof found in your home will dictate the time and budget required to convert your loft:

Traditional framed

Most pre-1960s houses boast traditional framed roofs, in which the ceiling joists, rafters and supporting timbers are custom-made and assembled on site. It’s relatively easy and cost-effective to open up the loft space under this type of roof by adding supports and strengthening the rafters.

Truss sectioned

This type of roof became the most popular after the 1960s thanks to its greater efficiency and affordability. The truss sections are built in a factory, allowing the whole roof to be erected and felted in a single day. The trusses are generally thinner (and cheaper), making them unsuitable for supporting the weight of a loft conversion without significant structural development – typically involving the addition of steel beams.

What permissions will you require to convert your loft?

Having assessed the suitability of turning your loft into a bedroom, it’s time to consider whether you’ll need any permissions or approvals to carry out the conversion.

 Planning permission

A loft conversion is considered a Permitted Development – and therefore doesn’t require planning permission, provided it adheres to outlined limitations and conditions.

There may well be rule changes, local restrictions, restrictions due to a conservation area or restriction for that building so up to date checks should always be made and professionals consulted before deciding not to apply for planning permission and allowing works to commence.

Limitations and conditions for a loft conversion include:

  • No more than 40 cubic metres of additional roof space for terraced houses, or 50 cubic metres for detached and semi-detached houses. Note that this includes any previous additions made to the roof space, even if carried out by a previous owner.
  • No extension further than the plane of the existing roof slope of the largest elevation fronting the road
  • No extension above the highest part of the house
  • No extension should overhang the outer face of the wall of the original house
  • No verandas, balconies or other elevated platforms
  • No materials of significantly different appearance to the existing house
  • Side-facing windows must be obscure-glazed and any opening must be 1.7 metres above floor level
  • Apart from in the case of a hip-to-gable expansion, any extension should – where practicable – be set back at least 20 centimetres from the original eaves
  • No roof extensions are allowed in designated areas, such as national parks and World Heritage sites.

For more information on this, visit Planning Portal, a joint venture between TerraQuest and the Department for Communities and Local Government.


Building regulations approval

Whether or not your project requires planning permission, a building control surveyor will need to inspect your conversion throughout the building process. Provided it meets the minimum standards, you’ll be granted a completion certificate after the final inspection. Visit the Planning Portal for guidance on how to gain approval.

 Separately, you should also bear in mind that if your home is semi-detached or terraced, you’ll need to tell your neighbours about your plans if the work falls under the requirements of the Party Wall Act.


Looking to add value to your property? Read our article on the activities that add the most value to a house.


Other things to consider when converting your loft

Based on the above, converting your loft no doubt seems like a win-win situation. However, it’s worth noting that there are also some significant potential downsides:


Potential damage

Any home improvement project can run into difficulties, some of which could even damage your house. For instance, with workmen trudging in and out of your property over the course of several weeks, there’s a good chance you’ll need to replace some of your carpets once the renovation has been completed – requiring further time and expenditure.


Living arrangements

If they run smoothly, loft conversions can take up to eight weeks to complete, and even the simplest conversion is likely to require a month of work. Obviously, any complications encountered along the way can add a significant amount onto this timeline. It can be extremely challenging for families to deal with this disruption, particularly as you may encounter extended periods with no electricity or plumbing.


Could your loft conversion put off buyers?

While a loft conversion can add to the price of your property, this isn’t telling the full story. Let’s say you’ve got a standard two-bedroom property. By converting the loft into a third bedroom, you’re now competing with non-converted three-bedroom houses in your area, many of which are likely to offer substantially more living space than yours. This will naturally impact the market value and could even make your house less appealing to some buyers.

Correct at time of publication (20th November 2018). The views and opinions expressed herein are those of the individual contributor and do not necessarily reflect those of the Chancellors Group of Estate Agents Ltd or its subsidiaries. References to legislation, best practice and other matters with legal implications such as fees, rules and processes are included for information and editorial purposes only and are not authoritative, nor should they be interpreted as advice. When in doubt you should only take advice from an industry professional or solicitor where appropriate. E&OE.

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