Loft insulation in Ridge

Reading what is there. Old material tells you a lot. It settles and compresses, goes patchy in the middle and missing at the edges, and takes on gaps where cables and pipework were pulled through. If the underside is grey and dry it has simply aged, and the new layer goes over it. If it is heavy, damp, black underneath or contaminated with droppings, it comes out, is bagged at the hatch and leaves with us, and the reason it is wet gets dealt with before anything replaces it.

What we lay. Mineral wool for most lofts, as glass wool rolls mostly, rockwool batts where the bay wants filling tight. Loose fill, blown or poured, where the joists are at awkward centres or the space is too tight to work a roll into. Sheep wool if you would rather. Where headroom has run out, PIR rigid board cut tight and taped at the joints, and a multi-foil quilt for the shallowest last stretch.

Two layers, and the second one crossways. One layer laid flush between the joists is where most lofts stop, and it leaves every timber conducting heat straight through the ceiling. The first layer goes between the joists and the second is cross laid over the joists, turned across the run of the first. Around 270mm all in is what a Part L U value comes to once it is laid rather than calculated, and there should be no joist tops showing when it is finished.

The air path, which comes first here. Insulation is taken to the wall plate and left and the eaves stay open, vent trays are fitted so the air gap cannot be choked so cross ventilation still gets from one eaves to the other. Block them and the vapour rising out of the house condenses on the cold underside of the covering instead. Insulating moves the dew point, interstitial condensation forms inside the layer where nobody can see it, and the result is wet material and black mould running along the rafters. Approved Document F carries the ventilation standard, A breathable membrane asks for a different detail and nothing more, and where the eaves cannot be opened a ridge vent often can be.

Services, hatch and rafter level. Covers rated for the purpose go over the recessed lights, and cables are lifted out and clipped over the layer, because wiring buried in insulation runs hot. A cold water tank and its pipework sit in colder air once the ceiling is done and want lagging. The hatch is insulated where nobody sees it and sealed round the edge, since an unsealed hatch pumps warm damp air straight up. Where there is no loft floor, a room in roof puts the insulation at rafter level in a warm roof, sloping ceiling and dormer cheeks carried through as one layer.

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 cottage with a trapdoor in a back bedroom, a bungalow with a hatch on the landing, and a house where the loft is already half boarded and full are three different mornings before material is laid, and each begins with work at height. 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.

Sitting this low, with water on three sides and heath beyond it, the air here carries more moisture for more of the year than it does a few miles inland. That does nothing to a loft on its own. What it does is shorten the margin. A roof space that only just ventilates will cope in a dry winter and will not cope in a wet one, and the first you know about it is droplets running off the underside of the felt onto insulation that then stays damp for months.

So on these houses the ventilation is not a detail at the end of the quote, it is the first item on it. We check that the eaves are genuinely open on both sides rather than on one, fit vent trays so the new depth cannot choke them, and seal the routes warm damp air uses to get up there in the first place: the hatch, the light fittings, the pipe and cable holes and the top of the stud walls. Only then does the depth go down. Where a roof simply cannot breathe at the eaves, a ridge vent is usually the honest answer, and we would rather price that than lay a thick layer over a problem.

We cover Ridge, Stoborough, Wareham, Sandford, Arne and Holton Heath, and the BH20 addresses around them, with Dorset Council responsible for planning and 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.