Flat conversion · England · 14 build-ups · 37 notes
Building Regulations specification for a flat conversion
Converting a house into flats is a material change of use, which brings the whole building within the Regulations and makes Part E the centre of the application. The specification carries the separating construction, the fire separation and the sound testing regime that a building control body will look for first.
Assembled in Specline from a library written to the Approved Documents, with the U-value working for every calculated element printed as its own section, and issued under your practice's own name.
What building control looks for
The questions the specification answers before they are asked
On a flat conversion
- The separating walls and floors between flats, their sound performance, and the flanking transmission around them.
- Pre-completion sound testing, and what happens if a test fails.
- Compartmentation between flats and the common parts, the periods of fire resistance, and the flat entrance doors.
- Means of escape from each flat and along the common stair, with the alarm system and the emergency lighting the common parts need.
- Which requirements apply on a change of use, and which do not.
The limits that apply — Approved Document L Volume 1
| New element (Table 4.2) | Maximum |
|---|---|
| Walls | 0.18 |
| Floors | 0.18 |
| Roofs | 0.15 |
| Windows | 1.4 (or WER band B) |
| Rooflights | 2.2 (or band C) |
| Doors | 1.4 (or DSER B/C) |
| Retained element (Table 4.3) | Threshold | Improve to |
|---|---|---|
| Roof, all types | 0.35 | 0.16 |
| Cavity wall | 0.70 | 0.55 |
| Other walls | 0.70 | 0.30 |
| Floor | 0.70 | 0.25 |
W/m²K. A new element meets Table 4.2. An existing element renovated as part of the work is improved where it is worse than the Table 4.3 threshold.
Part A · construction build-ups
The build-ups in the library for a flat conversion
Each is written layer by layer with named products and their alternatives, and each figure is what the build-up achieves when calculated to BS EN ISO 6946, or BS EN ISO 13370 for floors and basements, not the target it has to beat. Cavity walls, framed walls, floors, basements and roofs can also be configured layer by layer on the job.
| Group | Build-up | Achieves |
|---|---|---|
| Separating walls | ||
| SW | Separating Wall — Independent Lining to Existing Masonry | 43 dB |
| SW | Separating Wall — New Twin Independent Frame | 43 dB |
| Separating floors | ||
| SF | Separating Floor — Platform Floor with Independent Ceiling | 43 / 64 dB |
| SF | Separating Floor — Independent Ceiling Only | 43 / 64 dB |
| SF | Separating Floor — Existing Concrete Floor with Floating Floor | 43 / 64 dB |
| External walls | ||
| EW | Existing External Wall — Internally Insulated | 0.26 W/m²K |
| EW | Existing External Wall — External Wall Insulation | 0.27 W/m²K |
| EW | Existing Party Wall to the Adjoining Property | 0.26 W/m²K / REI 60 |
| Internal walls | ||
| IW | Internal Partition Within a Flat | — |
| Ground floors | ||
| GF | Existing Solid Ground Floor — Insulation Over Slab | 0.17 W/m²Klimit 0.25 |
| GF | Existing Suspended Timber Ground Floor — Insulated Between Joists | 0.17 W/m²Klimit 0.25 |
| Roofs | ||
| RF | Existing Flat Roof — Warm Deck Overlay | 0.15 W/m²Klimit 0.16 |
| RF | Existing Pitched Roof — Insulation at Rafter Level (Room in Roof) | 0.15 W/m²Klimit 0.16 |
| RF | Existing Roof — Insulation at Ceiling Level | 0.11 W/m²K |
13 of 14 carry a calculated U-value. A dash means the element has no thermal target: an internal wall, an intermediate floor, a foundation.
Part B · general notes
37 notes across 23 categories
Arranged in the order a building control officer reads a pack. One subject, one note: nothing repeats and nothing contradicts. Notes about a feature the project may not have — Existing Timber Frame External Wall — Upgrade — start off, and the review step names every one left off.
- Applicability
- Planning
- Consultations & Party Wall
- General Notes
- Site Preparation & Moisture
- Structure
- Separating Walls
- Separating Floors
- Ground Floors
- External Walls, Internal Walls & Roofs
- Internal Works
- Sound Insulation (Part E)
- Means of Escape & Fire Regs
- Windows & External Doors
- Ventilation
- Condensation (C2)
- Drainage & Waste
- Water & Sanitary
- Services
- Security (Part Q)
- EV Charging (Part S)
- Conservation of Fuel & Power
- Extra Notes & External Works
Straight answers
Questions about a flat conversion specification
- Does a flat conversion need sound testing?
- Yes, unless the separating construction uses a registered Robust Details arrangement, which is not normally available on a conversion. Pre-completion testing of a sample of the separating walls and floors is required under Approved Document E, and the specification states the performance standards the construction is designed to meet.
- Which parts of the Regulations apply to a change of use?
- A material change of use brings specific requirements into force for the whole building, not only the new work. The specification carries a category that lists which requirements apply on this change of use, and which do not, so the application states its own scope.
- Does the specification cover the common parts?
- Yes: the common stair, its fire doors, smoke ventilation and emergency lighting, the flat entrance doors, and the linings and roof coverings that external fire spread depends on.
Issue the flat conversion specification under your own name
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