Loft insulation in 1930s semi-detached houses
The classic between-the-wars semi usually has a generous, high hipped roof with plenty of room to insulate and board. The age of the roof is what to look at closely.
| Built | Roughly 1919 to 1939 |
|---|---|
| Typical roof | Hipped, steep, clay or concrete tiles, traditional cut timbers |
| Watch for | Old or no felt, chimney breasts, tanks, past insulation |
| Good for | Insulation plus raised boarding for storage |
A good loft to work in
Inter-war semis were built with cut-timber roofs: rafters, purlins and struts rather than factory-made trusses. That usually means a tall, open loft with space to move, lay insulation to full depth and fit raised boarding. Many have already been insulated once, decades ago, to a depth that was normal then and is thin now, so a top-up is often the job.
The roof covering
Originally, many of these roofs had no felt under the tiles, or a bitumen felt that has since become brittle. If the roof has been re-covered, it may have a modern breathable membrane. We look at which you have, because it affects how the loft is ventilated and whether rain can get through onto the insulation.
What to ask
- Is the existing insulation dry and worth keeping?
- Are the eaves clear for ventilation?
- Can the old water tank come out if it is no longer used?
- Is the joist size suitable for the storage you have in mind?
- Is there a chimney breast that needs insulating around safely?
Common questions
My semi was insulated years ago. Do I need more?
Can a 1930s loft be used for storage?
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