Engineered
to last.
Every Prefab Living Co structure is built to the same core specification — a 150 mm C24 timber envelope with 100 mm PIR insulation, 12 mm OSB sheathing, DPM vapour control and an EPDM single-ply flat roof. The result is a building that exceeds current UK Building Regulations for thermal, structural and moisture performance.
Wall envelope
A 150 mm C24 timber stud envelope, insulated with 100 mm PIR, sheathed externally in 12 mm OSB with a breather membrane, and internally lined with 12.5 mm plasterboard over a 500 g polythene vapour control layer. External cladding — brick, composite panel or timber — is fixed to a ventilated cavity on treated battens.
Flat roof
A warm-roof construction: 150 mm C24 joists with 100 mm PIR insulation, decked in 18 mm WBP plywood and finished with a fully-bonded 1.2 mm reinforced EPDM single-ply membrane carrying a 30-year manufacturer warranty. A polythene vapour control layer is fitted on the warm side, with a 50 mm service void under the ceiling.
Floor over concrete raft
A precision-poured 150 mm reinforced concrete raft (C25/30 with A142 mesh top and bottom) laid on a 150 mm+ MOT Type 1 sub-base. Two layers of 500 g polythene DPM sandwich a 150 mm C24 joisted floor with 100 mm PIR infill and a 22 mm P5 T&G chipboard deck ready for the client's chosen finish.
Representative 6 × 4 m extension.
Elevations shown for the standard 6.0 × 4.0 m rear extension at 2.65 m external height. Every project is bespoke — final elevations are issued as part of the individual planning & building-regs package with your chosen size, cladding finish and glazing configuration.
Every component certified.
| Code | Item | Specification | Application | Certification |
|---|---|---|---|---|
| T-01 | Structural timber | 150 × 50 mm C24 kiln-dried European whitewood | Studs · Joists · Rafters | PEFC / FSC |
| I-01 | Rigid insulation | 100 mm Celotex GA4100 (PIR) | Between studs, joists & rafters | BBA 15/5215 |
| S-01 | External sheathing | 12 mm OSB/3 sheathing board | External stud face | EN 300 / CE |
| M-01 | Vapour control layer | 500 gauge polythene DPM | Warm side of all elements | BS 6229 |
| M-02 | Roof membrane | 1.2 mm reinforced EPDM (Firestone RubberCover) | Flat roof — fully bonded | BBA 05/4246, 30 yr |
| M-03 | Breather membrane | Class W1 breathable wall membrane | External face of sheathing | BS EN 13859-2 |
| D-01 | Floor deck | 22 mm P5 T&G chipboard, glued + screwed | Structural floor deck | EN 312 |
| D-02 | Roof deck | 18 mm WBP structural plywood | Structural roof deck | BS EN 636-3 |
| F-01 | Foundation | 150 mm C25/30 reinforced concrete raft, A142 mesh top + bottom | Foundation | BS 8500 / EN 206 |
| L-01 | Internal lining | 12.5 mm plasterboard + 3 mm skim finish | Walls & ceilings | BS EN 520 |
Full compliance with Approved Documents A (Structure), B (Fire), C (Damp), E (Sound), F (Ventilation), L (Conservation of fuel & power) and Part O (Overheating).
Every build carries a 10-year insurance-backed structural warranty issued on practical completion.
Standard build achieves EPC B rating on completion; upgraded specification available for A rating.
Drawings indicative — not to be scaled from screen. Final construction details are issued as part of the building-regs package for each project and are subject to site-specific structural engineer sign-off. © Prefab Living Co.