Rooflight and skylight installation in Alresford

Establishing the roof structure

The single most useful thing to check before asking for a quotation, and it takes two minutes with a torch.

Rafters running from eaves to ridge with a horizontal purlin partway up and clear space between them is a traditional cut roof. Forming or widening an opening is ordinary carpentry, wide rooflights are possible, and the loft is convertible.

A repeating pattern of triangular frames with diagonal members crossing the middle of the space, joined by flat pressed steel plates, is trussed rafters. Those are engineered components in which the rafter, the ceiling tie and the webs work as one unit, and cutting any member sends load somewhere it was not designed to go.

With trusses, a unit narrow enough to sit between two of them at 600mm centres needs no structural work at all. Anything wider needs a structural trimmer designed by an engineer, and that is where the price steps up. It is also why a trussed loft is not convertible without replacing the roof structure.

Broadly, the earlier and mid century properties here are cut roofs and anything from the 1970s onward is likely trussed. A photograph looking up inside the loft settles it without a visit.

Coverings

Concrete interlocking tiles dominate, with clay on some of the older properties and slate on a few, on pitches typically between 30 and 35 degrees.

Interlocking tiles are profiled and need a deep flashing kit rather than the flat kit used on slate. A flat kit leaves open voids under the tile channels where it crosses them, water gets under within a season, and because it enters below the flashing it appears inside as a leak that seems to come from nowhere. It is the most common installation fault we find on other people’s work and it is invisible once the job is finished.

Ask any quoting installer which kit is specified for your covering by name and part number. A quotation that cannot answer that has not been written from a survey.

Coastal influence

Alresford is close enough to the Colne estuary that exposure is worth a thought on the more open positions, without being the dominant factor it is on the coast itself.

Stainless steel fixings rather than plated ones cost very little more and do not bleed rust down a roof in five years. On an exposed position, aluminium clad timber suits better than bare timber, because the cladding takes the weather and the timber stays dry behind it. And driving rain matters more than total rainfall for a roof window, which puts the weathering job on the underlay collar and the flashing kit rather than on gravity.

What we fit here

Roof windows into rear slopes for loft rooms and landings, which the cut roof properties take very well. Flat roof rooflights and lanterns over the rear extensions a great many Alresford houses have gained. Sun tunnels into internal bathrooms and hallways. And a growing amount of replacement work, because a lot of units went in during the 1980s and 1990s and sealed units last fifteen to twenty five years.

Extensions and the kerb

Where an extension is involved, the kerb decides whether the installation lasts. At least 150mm of upstand, the deck falling away from it so water cannot pond against the seal, and rigid insulation on the outer face of the kerb itself.

That last item appears on almost no quotation and matters more than the glass specification does, because an uninsulated timber kerb punches straight through the roof insulation around the whole perimeter of the opening. Ask directly whether it is insulated. It is the fastest way to tell who is detailing the job and who is fitting a unit.

Permissions and access

Most Alresford properties are permitted development: a rooflight is permitted provided it projects no more than 150mm beyond the plane of the roof and does not sit above the highest part of it, with additional restrictions on side elevations facing a boundary. The exceptions are individually listed buildings, which need consent regardless of slope or visibility, and flats, which have no permitted development rights at all.

Access is generally good, with off street parking on most roads and space to stand a tower at the rear. Two storey rear slope work needs scaffold, but it stands on private land, which avoids the highway licence that pavement scaffold requires in the older towns.

Obsolete sizes

Normal for anything of that age and entirely solvable. Adapt the opening to the nearest current size, usually within 40mm or 60mm, which leaves a standard size for the next thirty years and is the usual answer. Or find another manufacturer at the old dimension, which suits an opening that is awkward to alter. Or reframe entirely, which makes sense where the timber needs replacing anyway.

What nobody should do is force a unit into an opening it does not fit and pack the difference, which survives about a year before the frame goes out of square.

Glass or whole window

On some pitched roof windows the sealed unit is held by a removable bead and the glass alone can be replaced. Whether it is worth doing is a separate question.

Most of the cost of this job is getting to the window rather than the component. A twenty five year old frame has hardened seals, worn hinges and thermal performance two generations behind current, so new glass in it buys you modern glazing in a worn window for nearly the same money.

Frame under fifteen years and sound: replace the glass. Over twenty: replace the window. Any timber decay: replace the window, always.

Doing several together

Access is a fixed cost shared across everything done on the same visit, so two units replaced together cost meaningfully less than two replaced a year apart. Units fitted at the same time fail at about the same time, so if two of three have misted the third is not far behind.