Building regulations solutions: new insulation options for loft conversions, piling and foundation solutions for extensions, and how to meet the building regulations for fire safety with an open plan design
1). New insulation options for loft conversions
– U values : – walls (external walls/party walls) : new:0.28; upgraded solid walls :0.30;
upgraded cavity walls :0.55; flat roofs :0.18; pitched roofs (insulation at
ceiling level) :0.16; pitched roof (insulation between/under rafters) :0.18
A). Polyurethane : approx 100mm thick between joists, 30mm underlining them, but
take care to maintain a 50mm air gap between insulation and roof felt (with eaves
vents & high level tile/ridge vents) or use breathable roofing membrane if re-tiling.
B). Multifoil insulation tacked to rafters, battened and then plasterboarded, usually
need further 30mm polyurethane board underlining rafters
– take care as some BCB’s do not accept the TRADA certification
– take care as often multi foils aren’t certified for flat roofs, and only for
part of the external walls
2). Piling and foundation solutions for extensions
Standard foundations to about 2m are usually strip or trench-fill footings.
Poor ground conditions or building in clay subsoils near trees, may require very deep
foundations needing a designed solution.
A). Piling : specialist firms, soil samples or tests. Various kinds, bored, driven /
hammered. Mini- piles developed for small works with narrow access. Reinforced
concrete ground beams between pile caps.
B). Pad and beam : deep square pads about 1m2 at about 3m spacings with
reinforced concrete ground beams
C). Raft foundations : reinforced concrete slabs with toes : small extensions or
garages etc – can move out of horizontal so the BCB may not accept this for
3). How to meet the building regulations for fire safety with an open plan design
Lofts often have open plan ground floors, lounges and kitchens (medium to high fire
For 2 storey houses with a loft conversion, the Building Regulations Approved
Document B advocates use of sprinklers on Ground Floor and separation of Ground
and First Floor (fire resisting enclosure and fire door, usually at first floor level.
Alternatively a fire engineer can check travel distances, heights of rooms etc and may
confirm acceptability with escape through first floor windows and detection throughout.