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.
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.
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
- Knock-throughs between front and rear reception rooms
- Steel beam installation to remove the dividing wall
Trusted Open-Plan Conversions in Borehamwood
An open plan ground floor is a structural job wearing a decorating brief. We appoint the engineer, size and install the beam, 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.
- Heat loss and acoustics considered before the wall comes out
- Floor levels and thresholds evened out across the whole space
- Lighting circuits zoned rather than one pendant in the middle
- Paperwork and certificates handed over for when you sell
- Neighbours given notice before the noisy stages
- Honest updates if a date or a detail has to move