“How much does a 9×4 Gym Box cost?” — that’s the question Google rarely answers properly. Most websites only list the catalogue 8×3 and 9×3 models. Yet the majority of our clients order bespoke dimensions that don’t appear on any standard spec sheet.
Below is pricing based on real 2026 quotes for UK delivery — not figures spat out by a calculator.
Prices are in GBP, ex-VAT, for the unit delivered from our Polish factory to a UK site. The 20% standard VAT rate applies on top for most private buyers; if you’re buying through a limited company, ask your accountant about reclaiming it.
Why do clients choose bespoke dimensions?
Three reasons:
➜ The usable space in the garden is irregular — there’s no room for 11 m of length, but there is for 7×5
➜ The function needs a different proportion — a gym with a shower and WC needs more width than depth
➜ Budget vs. floor area — 7×5 = 35 m² costs differently to a long, narrow layout of similar area
How we price a custom Gym Box
The cost of the module depends on:
➜ Total floor area — the baseline for material cost
➜ Wall perimeter — mineral wool, cladding, flashing
➜ Number and type of openings — every window and door is a separate component
➜ Module height — 2,700 mm as standard; taller costs more
➜ Finish level — Basic, Standard, Premium
A module wider than 3 m (say 5 m) needs a different structural design to a narrow container — and that feeds into the price. The build itself (steel frame, 80–100 mm sandwich panel, U-values) is identical to our catalogue units; only the geometry changes.
Bespoke dimension pricing (GBP, ex-VAT, 2026)
Models up to 30 m²
| Size | Floor area | Module only (no equipment) | With Standard equipment |
|---|---|---|---|
| 6×4 m | 24 m² | from £28,800 | from £44,800 |
| 6×5 m | 30 m² | from £36,000 | from £52,800 |
| 7×4 m | 28 m² | from £33,600 | from £50,800 |
Models 30–45 m²
| Size | Floor area | Module only (no equipment) | With Standard equipment |
|---|---|---|---|
| 7×5 m | 35 m² | from £42,000 | from £60,000 |
| 8×4 m | 32 m² | from £38,000 | from £56,000 |
| 8×3.5 m | 28 m² | from £33,600 | from £49,600 |
| 9×4 m | 36 m² | from £43,200 | from £61,200 |
| 9×5 m | 45 m² | from £54,000 | from £76,000 |
Models 40 m²+
| Size | Floor area | Module only (no equipment) | With Standard equipment |
|---|---|---|---|
| 10×4 m | 40 m² | from £48,000 | from £68,000 |
| 10×5 m | 50 m² | from £60,000 | from £84,000 |
| 12×4 m | 48 m² | from £58,000 | from £82,000 |
| 12×5 m | 60 m² | from £72,000 | from £100,000 |
Indicative prices. The final quote follows once you confirm dimensions, finish level and specification. Delivery to your UK site is included in the bespoke quote; the foundation (a simple ground screw or slab base) is priced per site.
What pushes the price above the table?
The figures above are the lower end for a standard specification. Your project will cost more if you add:
| Option | Effect on price |
|---|---|
| Shower + WC fit-out | +£6,000–16,000 |
| Folding / sliding glass wall | +£4,000–10,000 |
| Slatted cladding (WPC or aluminium) | +£2,000–7,200 |
| Finnish sauna inside the module | +£8,000–16,000 |
| Wet underfloor heating | +£4,800–8,000 |
| Premium equipment (commercial machines) | +£8,000–20,000 |
| Extra ceiling height (> 3 m) | +£4,000–8,000 |
Real examples from 2026 quotes
Gym Box 7×5 m — private garden gym, recreation + training
Slatted cladding, mirrors, HEX LED lighting, air conditioning
→ from £45,200 (complete, excluding foundation and utility connection)
Gym Box 6×5 m — holiday let, guest fitness room
Corner glazing, equipment sized for guests, air conditioning
→ from £50,000–60,000
Gym Box 10×4 m with a combat-sports zone
Strength area plus a combat corner — heavy bag, mats, 60 kg of dumbbells, two 100 kg weight stacks, slatted cladding
→ from £57,200–60,000
Gym Box 12×4 m with an office corner
Module with electrics, no sanitary fit-out, equipment supplied separately
→ from £58,000 (module only)
Unmanned 24/7 community gym, 10×4 m — premium
Slatted facade, QR access system, CCTV, full commercial equipment
→ from £99,600–115,600
How much more do you pay for a bespoke size?
Comparison against the current catalogue models at a similar floor area:
| Catalogue model | Floor area | Price | Comparable bespoke size | Bespoke price |
|---|---|---|---|---|
| 9×3 m Standard | 27 m² | from £32,500 | 6×5 m (30 m²) | from £52,800 |
In practice the premium for going bespoke at a similar area is substantial — on these two specs it is over 50%, because a catalogue package is built in a series while a wider footprint needs its own structural design and a one-off build. Worth it when the function and layout genuinely call for it. If a standard 8×3 or 9×3 footprint fits your garden, the catalogue model is almost always the better-value starting point.
A quick note for UK buyers
Two things worth checking before you commit to a size:
➜ Planning — most garden gyms fall under permitted development, but the rules tighten on outbuildings over a certain footprint, near boundaries, or on listed/conservation sites. Confirm with your local planning authority. We cover this in detail in our garden gym planning permission guide.
➜ Foundation and access — a 10 m or 12 m module needs crane or HIAB access to the site. Tight side returns can rule out the longest sizes, which is another reason a wider, shorter footprint (7×5, 9×5) often wins.
Got a specific size in mind? We’ll quote it free of charge — answer within 24 hours.
➜ Get in touch with Gym Assistance
➜ Build your spec and get a price
➜ Container gyms — standard models
➜ How to choose your container gym size