Open-Plan Conversions Borehamwood

Open plan in a Borehamwood house means removing a wall that is holding something up, and sometimes extending at the same time. GS Renovation appoints the structural engineer, installs the beam to their calculations and finishes the space so the steel disappears. We coordinate the building control application and the inspections that go with it.

For Borehamwood, on London-derived ranges a knock-through finished as one room typically costs £3,000 to £8,000 or more, including the steel beam; Hertfordshire work generally runs below that. GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Borehamwood: 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 Borehamwood 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 Hertfordshire 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.

Knock throughs in Borehamwood's terraced houses

The 2021 Census recorded 4,468 terraced households across the four Borehamwood wards. A terraced plan is narrow, so the wall between front and rear rooms is doing structural work and blocking the only light path at the same time. Take it out on a properly sized beam and the ground floor reads as one room from front window to back door, with the light travelling the full depth.

A full knock through, taking in the wall removal, the engineer's fee and making good, runs £2,500 to £6,500 and above (indicative London ranges, MyBuilder and Checkatrade, 2026). A flush beam set up into the floor zone is a bigger job than a downstand hung under the ceiling, because the joists above have to be picked up and carried. That choice is made before the section is ordered.

Housing in Borehamwood

Of the 15,090 homes the valuation list records in Borehamwood, 2% were built before 1919, 8% between the wars and 90% since 1945; 36% are flats and 63% are houses. Opening up a terrace in Borehamwood usually lands one beam end on the party wall, and 38% of homes here are terraced.

How far back Hertsmere lets you go

3.35 metres is the number to know. Hertsmere states it is likely to refuse a rear extension that breaches the 45 degree line or extends more than 3.35 metres beyond the original rear building line. A clarification note published in April 2010 says approval may be given up to 3.35 metres deep from the original rear elevation, where a similar extension could otherwise be built as permitted development.

That matters when open plan means knocking through and pushing the back of the house out in the same project. The depth you can add sets the size of the finished room, which sets the beam layout, which sets the price. Working the planning position out before the structural drawings are produced is cheaper than doing it in the other order.

The 45 degree line and your neighbour's windows

It is drawn from their windows, not from your boundary. Hertsmere expects every extension to sit comfortably within a line drawn at 45 degrees from the nearest edge of a neighbour's habitable room or kitchen window. Only windows to habitable rooms and kitchens are taken into consideration, so a bathroom or landing window next door does not constrain you in the same way.

In practice the position of the house next door governs how far you can build, which is why two similar houses on the same street can get different answers. It is worth measuring before you commit to a layout. We flag it at survey stage, and where the line is tight we say so rather than letting you discover it from a refusal notice.

• Kitchen island services routed through the new floor
• Heat loss and acoustic considerations before the wall comes out
• Openings formed in stages to keep the home usable

VOA Council Tax stock of properties, March 2025, for Borehamwood Cowley Hill, Borehamwood Brookmeadow, Borehamwood Kenilworth and Borehamwood Hillside. Counts rounded by the VOA.

For the wider picture around open-plan conversion in Borehamwood, see home renovation in Borehamwood, open-plan conversion in Radlett, side return infills, converting a garage into living space, open-plan conversion anywhere in London and RSJ & Load-Bearing Walls.

Trusted Open-Plan Conversions in Borehamwood

An open plan ground floor is a structural job wearing a decorating brief. We appoint the engineer, install the beam they size, and finish the space so the steel sits in the ceiling line instead of across it. Where an extension goes with it, Hertsmere's design guide sets the limits and we establish that position before drawings are finalised. Free no obligation quotations.

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.