Open-Plan Conversions Mill Hill

GS Renovation opens up Mill Hill houses, from the compartmented interwar semis near the Broadway to the wide detached homes where the ground floor can lose most of its internal walls at once. We handle the steel, the stability, the fire escape strategy and Barnet building control.

In Mill Hill, a knock-through finished as one room typically costs £3,000 to £8,000 or more, including the steel beam (indicative London ranges, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Mill Hill: the structural engineer we appoint designs the steel, we install it, and building control signs it off.

How the job runs

1. Free site survey at your Mill Hill address, covering the walls, services and floor levels, and an itemised quote.
2. The engineer we appoint sizes the beam, and the work is registered with Barnet Council building control or an approved inspector. On a shared wall you serve the party wall notice as building owner; we supply the drawings.
3. Props in, opening cut, beam on padstones; then floors, heating and electrics are joined up.
4. Building control inspects the steel before it is covered. We finish the room, and the completion certificate follows.

Open plan in a wide Mill Hill house

The larger detached houses here take open plan well, because there is real width to work with. The catch is that same width. Removing the wall between the receptions and then the wall through to the kitchen takes out two lines of masonry that were bracing the house against sideways load as well as holding the floor up. The engineer looks at stability, not only at the beam, and the answer is often a goalpost frame with columns rather than a beam perched on a slender return of brickwork at one end.

Where the openings meet, the detail matters. A beam landing on another beam needs a connection designed by the engineer, and columns need a pad foundation dug beneath the floor rather than a padstone sitting on a slab that was never meant to take that load. Broken plan usually works better than one enormous room in these houses anyway. A retained nib, a Crittall style screen or a change in ceiling level keeps kitchen noise out of the sitting area while the light still runs the length of the plan.

Housing in Mill Hill

About 10,980 homes are listed for Mill Hill, and the mix is 56% houses to 44% flats, with 52% built after 1945, 38% in 1919 to 1939 and 10% earlier. 24% of homes here are terraced; opening up a terrace in Mill Hill usually lands one beam end on the party wall.

Open plan in a Mill Hill flat and the escape route

44% of homes in Mill Hill are flats, and opening up a flat is a different exercise from opening up a house. In a flat the hall between the bedrooms and the front door is normally the way out in a fire, enclosed by walls and doors that keep smoke from one room out of it. Knock the kitchen into that hall and the escape from the bedrooms runs through the room where a fire is most likely to start. Building control will want that answered on paper before the wall comes down, not raised at the final visit.

The answer varies with the layout. A flat where the bedrooms sit close to the front door may keep a short protected lobby and open everything beyond it. A deeper flat may need the kitchen kept behind a door, a different arrangement of rooms, or fire protection measures chosen by a fire engineer. The entrance door onto the common stair matters as well, since it protects everyone else in the block, and the freeholder will expect it left as a fire door. In Mill Hill, raise the escape question with the engineer and the managing agent at the first meeting, while the layout can still change.

Fire escape and sign off in NW7

The rule that trips people up is the escape route. Where a house has a floor more than 4.5 metres above ground, which usually means three storeys or a converted loft, the staircase should discharge into a protected hall, so knocking the hall into the kitchen puts your escape route straight through the room most likely to be on fire. In a plain two storey house the upper rooms can rely on escape windows instead, but building control still looks at the route. Building control will want that resolved before it signs anything off, usually with interlinked mains powered detection throughout, sometimes by keeping a protected route elsewhere, occasionally with an escape window. Far easier to design at the start than to argue about at completion.

The rest we run as one package. Barnet Council's building control, or a registered building control approver, inspects the beam bearings and the connections before they are boarded. Structural steel in a house normally needs 30 minutes of fire protection, which in practice is two layers of plasterboard rather than a skim coat over a bare flange. In a detached Mill Hill house there is often no party wall duty at all; in one of the paired houses near the Broadway there usually is, and you serve the notice as building owner with the drawings we supply.

• Heat loss and acoustic considerations before the wall comes out
• Rooflights and glazed roofs to bring light deep into the plan
• Beam depth checked against existing ceiling heights

VOA Council Tax stock of properties, March 2025, for Mill Hill Broadway, Mill Hill East and Mill Hill Park. Counts rounded by the VOA.

If you are weighing up options for your Mill Hill property, it is worth reading home renovation in Mill Hill, open-plan conversion across Barnet, side return infills, garage conversions, our London open-plan conversion page and Building Regulations Explained.

Why Choose GS Renovation in Mill Hill

Mill Hill owners choose us for open plan because we think about the whole ground floor rather than just the hole in the wall. Stability, the fire escape route, the beam connections and the finished ceiling line are considered together, built to the structural engineer's calculations and inspected by Barnet Council's building control. One team, one programme, and a house that stays liveable while the messy stage happens.

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254). Structural design is by the consulting engineer appointed to your project.