Container offices have gone mainstream. What used to be a niche solution for construction sites is now a serious option for garden offices, business park units, and temporary classrooms. Here's what's actually involved — costs, planning, and what Phil builds.
Which Container Size Is Right for an Office?
- 20ft — single office, approximately 11m² floor area, comfortably fits 1–3 people depending on layout. Ideal for a solo garden office or a small on-site operations room.
- 40ft — two-room office or open plan, approximately 24m² floor area, fits 4–8 people. Enough space for a reception area, desk run, and a small meeting corner.
- 40ft HC (high cube) — same footprint as the 40ft but with an extra foot of internal height. When you add insulation and internal lining, ceiling height drops — the high cube gives you more to work with.
Phil's recommendation: for a solo or two-person garden office, a 20ft is ideal and easier to site. For a team workspace or anything that needs to feel like a proper office, go for a 40ft HC.
What Does a Container Office Conversion Include?
Phil's standard office fit-out covers:
- Structural insulation — closed-cell spray foam or rigid PIR board to walls, floor, and roof
- Internal lining — plywood or drylining depending on spec
- Electrics — power sockets, LED lighting, heating circuit (Phil's electrician certifies the installation)
- Windows — typically one or two per side panel, powder-coated aluminium frame
- Personnel door — usually added to a side panel; end doors become internal access or are sealed
- Vinyl or laminate flooring over the existing hardwood container floor
- External weatherproofing — paint or cladding to your specification
Optional extras include air conditioning, MVHR ventilation, data cabling pre-installed, a kitchen unit, and WC (feasible on a 40ft with plumbing access). See the full container office page for what Phil can build.
How Much Does a Container Office Conversion Cost?
Phil's honest ranges based on what he's actually building:
- Basic 20ft fit-out (insulation, lining, electrics, windows, personnel door) — from £5,000
- Mid-spec 20ft (all of the above plus vinyl flooring, external cladding, heating circuit) — £7,000–£10,000
- Full 40ft fit-out (all of the above, two-room layout, air conditioning) — £12,000–£20,000+
Prices vary significantly by spec — what you put in is what drives the cost. Phil quotes on-site or by phone after a conversation about exactly what you need. Call 020 8226 0007 to discuss.
Do You Need Planning Permission for a Container Office?
The short answer is: it depends on how you're using it and where.
Temporary use on commercial land — typically within the permitted use class of the site — generally doesn't require planning permission. Permanent placement on residential land, or use that changes the character of the site, will likely require consent from your local planning authority. England and Wales have different rules, and permitted development allowances vary by location.
See the planning permission guide for a fuller breakdown. When in doubt, a quick call to your local planning department is faster than guessing.
How Long Does the Conversion Take?
- Simple 20ft fit-out — 2–3 weeks from order to delivery, depending on current workload
- Complex 40ft fit-out — 4–8 weeks for a full two-room build with optional extras
Phil's yard in Bexleyheath does the build. Once complete, delivery is by HIAB crane lorry to your site. If you need a new one-trip container as the starting unit, add a few days for sourcing. Grade A used containers are also a solid starting point for most office conversions at lower cost.
What Makes Phil's Conversions Different?
It's not a factory production line. Each conversion is built to the customer's specification — Phil talks through your exact requirements before he even quotes. He won't upsell you beyond what you actually need, and he won't quote a spec he can't deliver.
With 30 years sourcing containers and building conversions, Phil knows which shortcuts cause problems and which shortcuts are fine. He builds what he'd be happy to use himself — and he tells you honestly if something you want isn't worth the money.
Ready to discuss your project? See the container office page for more detail, or call Phil directly on 020 8226 0007.