Loft insulation in Beacon Hill

A bungalow puts almost the whole house under one ceiling. That makes the loft floor the main route for heat loss, which is why depth over your head pays back faster here than in a two storey house of the same size. What is usually up there is one layer of mineral wool, glass wool or rockwool, pushed between the joists and compressed thinner than the packet ever claimed. A second layer of roll goes over the top, cross laid across the joists, so the timber stops being a cold bridge. Two layers, around 270mm finished, is what gets a ceiling to the U-value Approved Document L asks of a renovated thermal element under Part L.

What is already there decides whether it stays. Wool that is only compressed and patchy gets straightened and covered. Loose fill that has drifted, anything contaminated by droppings and anything sitting wet comes out, bagged at the hatch, and leaves with us. Batts go in where joist spacing is awkward, sheep wool where somebody wants it. Access is the first thing we look at, since it is still work at height even indoors.

The eaves are the part that gets ruined. Insulation runs to the wall plate and stops. Beyond it is the air gap the roof breathes through, and pushing new depth into the eaves swaps a warm bedroom for a wet roof. A vent tray at each rafter holds that path open so the material still reaches the edge rather than stopping short and going missing where the cold gets in. Where the soffits are boxed solid and the underlay is old felt rather than a breathable membrane, the cross ventilation is not working and a ridge vent goes on first. Otherwise you get condensation on the felt and mould on the timbers.

Chalets are a different job. Where there is a room in the roof, the ceiling you stand on is not the surface losing heat. Sloping ceilings, dormer cheeks and the flat top all want rigid board, PIR such as Celotex cut tight between the rafters with a clear gap above it, a second layer under, then a vapour control layer taped so warm air cannot get into the build up and find its dew point inside the timber. That is a warm roof. In a room in roof with almost no depth to spare a multi-foil quilt earns its place.

Then everything else up there. Downlighters and any other recessed light take fire rated covers, wiring is clipped above the new layer rather than buried in it, and the cold water tank and its pipework get lagging now they sit out in the cold. Storage is planned: loft legs and a raised floor over the insulation, a platform boarded where you need one, the hatch insulated and draught sealed, the loft ladder checked against the new floor.

No rate per square metre, because the floor area is the easy part and the awkward edges are where the time goes.

Getting to it. A bungalow with the hatch in the hall, a chalet with rooms already in the roof, and a two storey house with the hatch over the stairwell are three different jobs. A hatch on a landing you can stand a ladder under is one job. A hatch over a stairwell, a crawl space you can only move through on your knees, or a loft full of boarding that has to come up and go back, is time before any material is laid.

What is up there now, and what it is sitting on. Old material that has to come out, be bagged and taken away is a cost before anything new goes down, and so is a loft full of boxes that has to be emptied and put back. Joists at 400 centres with a flat run across them is a different afternoon from a trussed roof full of bracing.

Ventilation, and the edges nobody reaches. Insulation stops at the wall plate and the eaves have to stay clear, or you trade a warm bedroom for a wet roof. Getting depth right into the corners and around the hatch, boxing over downlighters and lagging anything that now sits in the cold, is most of the labour. Approved Document L sets what the work is expected to reach.

Comparing quotes? Ask what depth is actually being laid and in how many layers, whether the old material is coming out or being covered over, whether the eaves are being kept clear, what happens to anything you store up there, and whether the hatch and the pipework are included. Two quotes for the same job are usually two different jobs.

We cover Beacon Hill, Sturminster Marshall, Lytchett Minster, Upton, Corfe Mullen and the BH16 addresses around them, with Dorset Council for building control. You are dealing with Bournemouth Roofing & Building, the trading name of Bournemouth Roofing & Building Ltd, registered in England and Wales, company number 15471719, which you can look up in a minute. Thomas Hannen's business, and he is the one who comes out to price the job, not a salesman. A verified customer's 10 out of 10 on Checkatrade. The visit and the written quote are both free.