Mezzanine extensions:adding a ‘floor between floors’ can add more value than a loft conversion

Adding an extra level within an existing space attractive - creating a split-level room - is the improvement that gives you the best return on your investment.

Adding a mezzanine floor may not be the most obvious home improvement choice, but it could be the most cost-effective way of increasing both floor space and value, a new study shows.

A mezzanine means a floor between floors — an extra level inserted within an existing space to create a split-level room.

Today’s research by home remodelling company Harrington Grey compared the cost of 10 popular home improvement projects and the average value they add to a property, to calculate the typical return on investment.

Researchers found that a 248sq ft mezzanine would cost about £9,500 to install, but could add 10 per cent to the value of a home. For a typical London house worth £700,000, this works out as a return on the original investment of 640 per cent. “A mezzanine also gives you a very attractive airy, open effect,” adds Duncan MacLeod, managing director of Harrington Grey.

Wood’s good: a timber mezzanine in a listed South Kensington flat, by Hogarth Architects

The next best improvement, according to the report, is to demolish interior walls to create an open-plan space. The £2,500 cost of the work could hoist the value of a home by two per cent, giving a return of 520 per cent.


Based on a London house priced £700,000

Cost of project


Increase in value (%) New value


Return on Investment (%)
1 Mezzanine floor  £9,500  10  £770,000   640
2 Open-plan living  £2,250  2  £714,000  520
3 New kitchen  £9,000  6  £742,000  370
4 New bathroom  £5,000  3  £721,000  320
5 Loft conversion  £37,500  20  £840,000   270
6 Basement excavation  £45,000  20  £840,000  210
7 Internal decoration  £5,000  2  £714,000  180
8 Side return or kitchen extension  £60,000   20  £840,000   130
9 External decoration  £3,000   1  £707,000   130
10 Replace eight windows  £13,200   2  £714,000   100

Loft extensions, basement digs and side return extensions each add the most value to a property: 20 per cent according to the study. But the higher cost of these improvements — £37,000 for a loft; £45,000 for upgrading an existing basement into a usable room, and £60,000 for a side return kitchen extension — means a lower return on investment.

Pure industrial chic: Sadie Snelson Architects created a dramatic mezzanine level for a warehouse apartment in Clapton

To insert a mezzanine level into an existing room you need a minimum ceiling height of 13ft-14ft. So, while brilliant in a barn conversion or a loft apartment, such a project isn’t always possible in a regular flat or house.

Sadie Snelson, director of Sadie Snelson Architects, created a dramatic and beautiful mezzanine level for a warehouse apartment in Clapton, east London.

The owner wanted extra floor space without losing the impact of the double-height living room, which had 16ft ceilings. The solution was to leave part of the space open but build a timber and plasterboard mezzanine supported on existing steel columns and by wires hooked to the ceiling above the kitchen.

The room is used as a living room and occasional guest room, because one shortcoming of mezzanines is that they are open. Perfect for a study or living room, less than ideal for a bedroom.

Snelson’s mezzanine is pure industrial chic, but the concept can work in historic homes, too. Hogarth Architects removed a false ceiling from a Grade II-listed flat in South Kensington, and inserted a timber mezzanine above the kitchen, which overlooks the now double-height living space.

Award-winning: David Mikhail Architects extended and reconfigured this terrace house in Hoxton (Tim Crocker)

If you don’t have the benefit of towering ceilings, then a mezzanine bedroom, with a sleeping platform above and main room below, could still be an option.

Platforms are usually built from timber and/or metal and must be strong enough to bear the weight of a divan and a person or two. A balustrade will be needed to make this sleeping arrangement safe.

A sleeping platform, says MacLeod, requires a more modest ceiling height of about 10ft. “It is not going to add the same value as adding floor space, but if you need more space it is a really good way of finding it.”

A really low-cost alternative is Ikea’s white-stained StorÅ bedframe, priced £229. This 5ft-wide bed is raised 5ft 8in off the floor and has ladder steps, giving room for a sofa or desk below — an ideal space-saver for a studio flat or in a guest room.

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