How is an underground car gallery built?

Stage one is a private visit

We start at the house, not at a desk. We walk the garden, the drive and the approach. Then we listen.

The collection shapes everything. We ask how many cars there are, which eras, and how often they move.

A car driven each weekend needs a quick way out. A car laid up for winter can wait for a lift.

We also look for the route down. It may be a drive-through car lift, a ramp, or both. Our guide to car lifts for the home compares the options.

Stage two is feasibility

Feasibility answers one question. Can this gallery be built here, and what does it involve?

It starts with surveys. A ground investigation shows the soil and the groundwater. A tree survey maps the roots to protect.

A utilities search finds what runs under the lawn. A measured survey fixes the levels of the house and garden.

Our engineers then choose how to hold the ground back. You receive a costed proposal and a programme before anything is committed.

Our underground garage cost guide explains what sets the budget.

Stage three is concept design

The concept fixes the bays, the route down and the second route out. Every BELOW gallery has an independent second way out.

The lift is drawn early. Its pit, its travel and its platform shape the whole room.

Lift makers publish planning guides with these sizes. Our car lift dimensions guide sets them out.

This is also when the view is decided. Some clients want to see the cars from the house. Others want the gallery to feel like a separate world.

Stage four is planning and party walls

Each council writes its own basement rules. They differ from street to street.

Kensington and Chelsea limits how far a basement may extend under a garden. Westminster asks for at least 1m of soil over a basement roof.

Camden asks for evidence on groundwater and ground movement. Outside London, planners often ask about the setting of the house and its trees.

Our planning permission guide covers both.

A dig near a neighbour may need notices under the Party Wall etc. Act 1996. We serve them early, so the awards are in place before work starts.

Stage five is technical design

Now each system is designed in detail. The structure, the waterproofing, the air, the fire strategy, the power and the security.

Waterproofing follows BS 8102, the code of practice for structures below ground. It is designed in layers, so one failure does not reach the cars.

Our waterproofing guide explains how.

A sealed room needs mechanical air. Approved Document F sets the ventilation guidance.

Our air and climate guide explains how we keep humidity steady for stored cars.

Fire safety follows Approved Document B. The gallery is separated from the house. Detection links to a monitored alarm.

Stage six is construction

The build follows the same order every time. It starts with the enabling works.

Trees are protected, neighbours are monitored and the site is secured. Then come the walls that hold the ground back.

The dig follows, then the base. The structure is sealed and the lift pit is formed.

Services come next: air, power, drainage and security. The lift is then installed and tested.

Finishes come last, once the dusty trades have left. Stone, oak and light go in when the room is clean.

Stage seven is commissioning and handover

Every system is commissioned before a car moves in. The lift maker tests the lift.

The air, the alarms and the pumps are run under load. Any fault is fixed before handover, not after.

You and your staff are shown how each system works. A service contract starts on the first day.

Then the cars arrive. We are there for the first drive down.

What you decide at each stage

At the visit, you decide what the gallery is for. At feasibility, you decide whether to proceed.

At concept, you choose the route down and the view. At technical design, you choose finishes and systems.

During the build, decisions are few. The design is complete before the dig begins.

Who does what

A gallery needs architects, structural and geotechnical engineers, and a fire engineer. It also needs a lift maker, a waterproofing specialist and a planning consultant.

BELOW brings them into one team with one programme. You have one point of contact from the first visit to the last service.

Where to start

The first step is a private conversation. It costs nothing and commits you to nothing.

Use the consultation form below, or read the BELOW Standard first.

BELOW is part of NU Projects. NU has designed and built in prime London since 2010.