Can I Convert my Loft?

How to assess whether your attic is suitable for conversion
Chris Bates, Editor of Build It magazine
by Chris Batesmith
11th October 2017

Before you put any cash into your attic, it’s worth getting an idea of how easy it would be to repurpose as living space. These simple checks will give you a good indication:

Is there enough height?

The first step in assessing a loft’s potential is to check how much headroom is available. This should be measured from the top of the floor joists to the underside of the ridge beam.

A comfortable threshold is at least 2.4m. You may be able to get away with just 2.2m in some cases but the finished floor and ceiling will eat into this, leaving you with around 1.9m or 2m on completion, which could feel claustrophobic. See the box on page 86 for advice on how to increase height.

The main limiting factor is the building regs related to staircases. These are slightly relaxed for lofts but still require a minimum of 1.9m headroom at the centre of the flight, and 1.8m at the edges (to account for sloping roofs).

What’s the roof pitch like?

As a rule, the steeper the pitch the easier conversion will be, as there will be more usable space available. According to Velux, if your roof has a 35° gradient, you’ll need an 8.5m span to complete a rooflight conversion; as opposed to just 6.5m for a 45° pitch. Switching to a large dormer or other extension changes these parameters, but bear in mind that you won’t be able to raise this above the existing ridge height without securing full planning consent.

Do you have a cut roof or trusses?

Most roofs built before the 1960s were cut on site and assembled using thick rafters, joists and purlins – with minimal battening to get in the way of the main void. Assuming there’s enough head height and a decent pitch, these traditional cut roofs are often relatively easy to convert.

In more modern homes, Fink trusses were (and still are) commonly used. These are value engineered, so they use the minimum amount of timber and feature a distinctive W-shaped web for bracing (which has the effect of blocking the roof void). As a result, a little more engineering has to go into the conversion – and you’ll almost certainly need at least 2.4m of clear headroom to enable this type of project.

What condition is the space in?

Any signs of disrepair will need to be remedied prior to conversion. Typical issues include rot in the timbers, broken tiles and undersized rafters. These aren’t likely to scupper
a project, and once discovered you’ll probably want to deal with them anyway. But you do need to be clear on the costs to ensure your scheme will still be economically viable.

Are there any obstructions?

In older properties, one common obstacle to conversion is the presence of water tanks as part of the central heating setup. These can usually be moved to a more discreet location, or you could switch to an unvented cylinder that runs off mains pressure, thus negating the need for a tank.

Chimney stacks can sometimes be removed, subject to planning, but unless they’re really blocking the space, it might be better to look at how you could turn them to your advantage. Examples at gable walls may present the opportunity to include alcove shelving or built-in storage either side, for instance.

Closer Look: Bungalow extension & loft conversion

Location: Surrey
Type of project: Dormer loft conversion and 1.5-storey
Floorspace added: 50m²
Build cost: £25,000 (loft only)

Bungalow extension and loft conversion

When Rachel and Steve Bennett bought a rundown semi-detached bungalow, they were keen to extend as well as to convert the loft space to make it a better fit for them and their three teenage children. The scope of their scheme meant planning consent was a necessity, which was won without major issues.

The couple decided to use the TeleBeam system to enable the conversion. “We visited a local property where it had been used,” says Rachel. “Compared to the stories we’d heard from friends who’d used traditional methods that required sky-high scaffolding and big apertures in the roof, it sounded much more straightforward.”

The clever TeleBeam system involves inserting a series of bespoke manufactured telescopic metal beams to replace the floor joists, before fitting vertical studs near the eaves to replace the existing bracing (which is then cut out).

This results in minimal floor build up, preserving as much headroom as possible. It also requires very little interference with the roof covering – typically, just a few rows of tiles need to be removed. “In our case, the whole house was stripped out so we decided to insert the beams through the exposed part of the roof and directly from the ground floor,” says Rachel. “The whole process took a matter of days, with the TeleBeam team liaising closely with our builders to ensure a smooth process on site.”

To provide natural brightness, two rooflights were inserted above the staircase and another in one of the three attic bedrooms. A sun pipe was fitted above the upstairs bathroom, and the two other bedrooms feature glazing at the gable apexes. The loft was insulated at rafter level with a multi-layered foil and foam product, then closed in with plasterboard. The floor structure is fitted with Rockwool and boarded with tongue-and-groove decking to reduce noise transfer.

Main image: This 3D illustration by Julian Owen Architects shows the importance of having enough centre-point ceiling height – as sloping roofs will always limit the extent of usable living space

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