LOFT CONVERSIONS

Which conversion suits a Cardiff house

The type of conversion you can have is decided by your roof, not by preference. Cardiff's housing stock falls into a few recognisable groups, and each one tends toward a particular answer.

• Victorian and Edwardian terraces — Roath, Canton, Cathays, Grangetown. Traditional cut roofs with usable height at the ridge, usually converted with a rear dormer. The party walls on both sides do the structural work, which is why terraces are often the most straightforward of the lot.
• 1930s semis — Whitchurch, Llanishen, Heath, Rhiwbina. Hipped roofs that slope on three sides, so the usable floor area is small until the hip is squared off. A hip-to-gable, usually paired with a rear dormer, is the standard route.
• Post-1965 estates — much of the outer city and the Valleys. These typically have trussed rafter roofs, where the W-shaped webs cannot simply be cut out. They convert, but they need a steel or a proper structural redesign first, and that shows in the price.
• Bungalows — often the strongest return of the lot, because you are usually adding an entire floor rather than a room.
• Conservation areas — a mansard or an internal Velux conversion is frequently the only form that will get consent, since it alters the roofline least.

Do you have the height?

Measure from the top of the existing ceiling joist to the underside of the ridge. As a working rule you want around 2.2m before anything starts, because the new floor structure builds up from below and the insulation comes down from above, and the finished room has to keep roughly 2m of headroom over the stairs. Less than that does not rule a conversion out, but it moves you toward lowering ceilings in the rooms below or raising the roof — both of which change the job from a conversion into something closer to a rebuild.

Planning permission, and when you do not need it

Many loft conversions in Wales are permitted development and need no planning application, subject to volume limits — commonly in the region of 40 cubic metres of added roof space on a terrace and 50 on a semi or detached house. The conditions matter more than the numbers: no extension forward of the roof plane facing a highway, materials similar in appearance to the existing house, no balconies or raised platforms, and side-facing windows obscure-glazed and non-opening below 1.7m.

Permitted development rights are removed in conservation areas, on listed buildings, and on some estates carrying an Article 4 direction. Cardiff has several conservation areas, so it is worth checking your address against the council's map before you design anything. Where rights have been removed, you are not blocked — you simply need a full application, and the design needs to be sympathetic. We would rather establish this at the start than after drawings are paid for.

Whether or not you need planning permission, you need Building Regulations approval either way. Those are two different consents, and the one people skip is the one that causes trouble at sale.

What Building Control will be looking at

• Fire escape. Adding a third storey turns your staircase into a protected escape route: fire doors to habitable rooms off the stairwell, 30-minute resisting construction, and mains-powered interlinked alarms.
• Structure. Ceiling joists were not designed to carry a floor. New floor members span between load-bearing walls, usually clear of the existing ceiling.
• Insulation and ventilation. The roof build-up has to hit current thermal standards while keeping a ventilation path, or you trade a cold loft for a condensation problem.
• Stairs. A fixed staircase, not a ladder, with defined pitch, going and headroom — which is usually the single hardest thing to fit into a Victorian terrace.

What drives the price

Loft conversions vary more in cost than almost any other domestic job, and the variation is structural rather than cosmetic. The things that move the number are: whether the roof is a cut roof or trussed; how much dormer you are building; whether a steel is needed and how it gets into the house; where the staircase lands and how much of the floor below it consumes; whether you are adding an en-suite and how far it sits from the existing soil stack; and whether the electrical supply and consumer unit can carry another floor.

We price these separately rather than quoting a rate per square metre, because a square metre of trussed roof with a steel and an en-suite is not the same product as a square metre of Velux conversion in a terrace. If you want a number early, the useful first step is a site visit to establish the roof type and the stair position — those two answers set most of the cost.

How long it takes

A straightforward rear dormer on a traditional cut roof more commonly runs six to eight weeks on site. A hip-to-gable with a dormer, or anything involving a trussed roof and structural steel, tends toward eight to twelve. Add lead-in time before that for drawings, structural calculations and Building Control, and longer again if a planning application is needed. Most of the noisy, disruptive work is in the first fortnight, and the house stays habitable throughout on the majority of jobs.

Where we work

We cover Cardiff and the surrounding area, including Roath, Canton, Whitchurch, Llanishen, Lisvane, Radyr, Heath, Birchgrove and Caerphilly. For loft conversions in Penarth, Barry and the Vale of Glamorgan, our sister company All Aspects Construction covers that area.