Loft Insulation for 1920 to 1965 Homes

Homes from the interwar and early post-war years

The houses built between the wars and into the post-war rebuilding are some of the most familiar in Britain: bay-fronted semis, long terraces and solid, sensible family homes. In the loft they tend to share a straightforward pitched roof over a reasonably accessible space, which usually makes them good candidates for insulation. What varies is the history of what has already been done up there.

What we usually find

The most common situation is an existing layer of old wool, often only 50–100mm, laid when standards were lower. It may have settled, compressed unevenly or been pushed aside during other work. That is well short of the 270mm benchmark used for wool-based loft floors today, so a top-up is frequently the right answer — provided the existing material is dry and in sound condition.

Where the old insulation is damp, contaminated or in poor shape, it makes more sense to remove it first and lay a fresh installation on a clean surface.

DIY boarding and storage

Homes of this age have very often had a homeowner lay chipboard straight across the joists for storage. It is a reasonable thing to have done, but the boards usually sit too low and crush the insulation underneath, so it stops working properly. A raised boarding system lifts the storage deck clear of the build-up, keeping both the storage and the insulation.

Ventilation, felt and water tanks

Roofs from this period were not built with modern ventilation detailing. Many have bituminous roofing felt beneath the tiles, and some have none at all. Packing insulation into the eaves can block what little airflow there is and encourage condensation, so we keep the eaves clear and consider ventilation alongside the insulation.

Cold-water tanks are common in these lofts. Insulation should go under and around the tank, not beneath it in a way that leaves it exposed to freezing — the aim is a warm supply and a well-insulated ceiling. We also look for older or perished wiring, which is worth noting before any new material is laid, along with any downlighters or junction boxes that should not simply be buried under a fresh layer.

Access is another thing worth mentioning. Many homes of this age have a small, awkward hatch, sometimes still the original, and it may be uninsulated or poorly sealed. An unsealed hatch is an easy weak point in an otherwise well-insulated loft, and draught-sealing and insulating it is a small job that finishes the work off neatly.

Choosing a material

Mineral wool is the usual, cost-effective choice for a loft floor of this type. Recycled plastic is a lower-irritation, sustainable alternative that some homeowners prefer. The right material depends on the specific roof and loft — its ventilation, its condition and how the space is used — rather than on the decade the house was built.

What to expect from an assessment

We measure the existing depth, check the condition of any current insulation, and look at the hatch, pipes, tank and wiring. We check the eaves and roof covering and note any signs of damp. You then receive a written recommendation and quotation before anything is agreed, so you can see exactly what we suggest and why.

Final suitability always depends on that in-person inspection. If you would like a sense of the numbers first, our loft insulation cost guide explains the main factors, and our guarantees page sets out the cover included with our work.