Commercial Space Planning: Why Your Business Can’t Ignore It

Commercial space planning sets three big costs

Most people think the plan is about where desks go. On commercial jobs, it decides three things that cost far more than furniture.

Get any of them wrong and you pay twice. Once on paper, and again to put it right on site.

The first decision is how much space you take

Rent, rates and service charge are paid on area, year after year. The fit-out is a one-off. So getting the area wrong is the costliest planning mistake. And it is made before the lease is signed.

A plan drawn on the actual floor is called a test fit. It tells you four things:

1. Whether you fit at all. Count desks, meeting rooms, storage, kitchen, plant and the routes between them.
2. How much of the quoted area works. Columns, cores, deep floors and awkward corners all eat into it.
3. What the building costs to run. Service charge, rates and energy follow the area you take, not the area you use.
4. How much room you have to grow before you must move again.

Two buildings with the same area can seat different numbers of people. Test two or three shortlisted buildings this way. The choice usually makes itself.

How much space each person needs

There is one legal minimum and one industry benchmark. HSE guidance says each person needs at least 11 m³ of room volume. Any part of a room over 3.0 m high counts as 3.0 m. HSE is clear this is a minimum, and it doesn't cover meeting rooms.

The British Council for Offices recommends 10 m² per person for general workspace. It used to allow 8 m². Real density depends on how your team works, so plan for your busiest day, not the average one.

The second decision is what the fit-out costs

The plan sets the scope. The scope sets the price and the programme. These plan choices move the most money.

1. Walls. Every enclosed room adds partitions, doors, lighting, ventilation and fire alarm changes. On a Cat A floor, small rooms mean reworking a ceiling grid built for open plan. See our guide to Cat A and Cat B fit-out.
2. Wet areas. Kitchens, tea points and WCs far from the existing drainage need new runs, pumps or floor works.
3. Plant and extraction. In a restaurant, the extract route fixes the kitchen. Everything else is planned around it.
4. Phasing. In an occupied building, the plan decides what can be built while people keep working.

At Portsoken House reception in Aldgate, the plan for 70 m² included structural changes. We rebuilt the lift surrounds and added a shop window for daylight. The offices above stayed occupied. So the plan also had to work at night and at weekends. We rebuilt it in 12 weeks with no disruption to tenants.

The plan set the programme, and the programme set the cost.

The third decision is which consents you need

A layout is not just furniture. It has to work for everyone who signs it off.

1. Building control. New partitions, WCs and services are usually building work. Escape routes (Part B) and access for disabled people (Part M) both follow the plan.
2. The landlord. Almost any alteration in a leased building needs a licence for alterations. A clear plan early makes it a formality.
3. Planning. Works that affect only the interior are not development. But new ductwork, plant or a new shopfront can need permission.

The use class matters too. Offices, shops, cafés, restaurants, gyms and clinics all sit in Use Class E. Moving between them generally needs no planning permission for the use. Pubs, bars and takeaways sit outside it.

Check all three before the plan is fixed. Otherwise you find out during the build, when changes cost the most.

Each building type plans around something different

The principle is the same everywhere. What you plan around is not.

Offices: plan for the busiest day

At Beaumont House in Kensington, the client had five weeks left on their lease. More than 150 staff had to move. We demolished walls to make one open-plan floor of 750 m². Frosted glass partitions created smaller rooms for private meetings. Data ran under the floor to every desk. It was built in three weeks.

Compare the main types of office layout before you choose one. For style ideas, see our office design trends for 2026.

Converted buildings: the structure leads

At Portsoken House, an abandoned warehouse became 1,550 m² of offices over two floors. The rest of the building stayed let. The plan worked with the existing floors, which we levelled. It added a new entrance, kitchen and WCs.

Railway arches and warehouses: plan around what you can't touch

At Drake's, nothing could be drilled into the railway arch. So we designed a self-supported internal build. Every zone was mapped to how the teams work: offices, kitchen, photo studio, production, storage and dispatch. The smaller, better-planned space cut rent, utilities and running costs.

Planning too late costs a redesign

Medusa in Knightsbridge came to us at RIBA Stage 2. The concept and 3D visuals existed. The cost of building them had not been tested. Because design and construction sit in one team, we could price the concept early. We then adapted the design so it fitted the client's budget.

It worked. But it was rework that an earlier plan, with cost in the room, would have avoided.

Who should do your space planning

You can sketch a first layout yourself, using our guide to what office space planning is. For a small office move, that may be enough. Once the plan touches the lease, the structure, the services or the consents, you need more.

You need someone who knows what each line costs to build. That is a core part of what a commercial contractor does.

That is why we plan and build as one team. The person drawing the layout talks to the person pricing it before it reaches you. See our office design and space planning service, or commercial fit-out and refurbishment for other building types.

Five checks before you commit to a building

Every one of these can be checked on site. Bad answers are far cheaper to hear before you sign than after. Send us the address or the floor plan and book a site visit. We'll tell you what fits and what it will involve.