Site preparation to our specification
The base your building stands on, priced before you pay your balance.
Your building deserves more than a concrete slab. It deserves the right base for your ground, your building and how you use it.
The base is not included in the build price. See our Delivery & Installation terms.
What's in the build price
Included as standard
Every building in our configurable range is priced to include delivery to your address and full professional installation. The base is quoted separately, and there are no hidden charges on standard sites.
Included in every build
- Delivery to your address
- Professional installation included
- Building anchoring to your prepared base
- Doors, windows, guttering fitted
- Part P electrical certification (if you add electrics)
- Delivery date confirmed once deposit paid
Not included (quoted separately)
- The prepared, level base or foundation
- Excavation, levelling and drainage
- Non-standard site access or long electrical runs
Site extras are quoted from your three site photos before manufacture begins. You can cancel for a full refund any time before you pay your balance. This does not affect your statutory rights.
Specified, not guessed
How we determine your foundation
Every VeltHaven building is assessed individually. The correct foundation system is not a menu choice — it is determined by the conditions on your site and how the building will be used.
What the assessment considers
- Building weight and dimensions
- Soil bearing capacity and ground type
- Drainage, groundwater and frost protection
- Site access and slope
- Future loading — and for garages: vehicle loads, workshop equipment, car lifts, EV weight
Systems the specification may call for
Depending on the assessment, the right system may be a reinforced concrete slab, a strip footing, or ground screws — a fast, no-cure, reversible steel-screw platform that suits slopes and leaves no permanent change to your garden. The specification confirms which is correct for your building.
Send your three site photos and we will advise the right foundation and give you a guide price before you commit.
To our specification
The VeltHaven Reinforced Foundation
Where a reinforced foundation is specified, the specification for your ground is what governs. Our default specification for each building is set out below; nothing here is a blanket promise.
Why the detail matters
Thickness and reinforcement vary with ground and load — under-specify and a base cracks or settles; over-specify and you pay for concrete you do not need. A compacted sub-base spreads the load evenly. Drainage and a damp-proof membrane keep moisture out of the floor. Expansion joints and correct curing control cracking. A dead-level finish is what lets doors and sliding walls run true for years.
At this level of investment, the detail is the point — a level, dry, correctly-loaded base is what protects the building.
Our base specification
What base does each building need?
Two families. Steel garages sit on a standard slab. Insulated garages and garden rooms sit on an insulated slab — and garden rooms get the thinnest slab, because they carry no vehicles. The exact thickness and reinforcement are confirmed for your ground and your load. This table is our default, not an engineering design. If poor ground needs an engineer to check it, that is an extra cost.
Steel garages — standard base
| Building & use | Slab | Concrete | Mesh |
|---|---|---|---|
| Cars and storage | 125 mm (100 mm absolute minimum) | C25/30 | A142 |
| Double door, SUV or VAN height, 4x4s or vans | 150 mm | C30/37 | A193 |
| Workshop, car lift or heavy equipment | 150 mm minimum; an engineer checks the lift posts, at extra cost | C32/40 | A252 |
Cars and storage
- Slab
- 125 mm (100 mm absolute minimum)
- Concrete
- C25/30
- Mesh
- A142
Double door, SUV or VAN height, 4x4s or vans
- Slab
- 150 mm
- Concrete
- C30/37
- Mesh
- A193
Workshop, car lift or heavy equipment
- Slab
- 150 mm minimum; an engineer checks the lift posts, at extra cost
- Concrete
- C32/40
- Mesh
- A252
Insulated garages and garden rooms — insulated base
| Building & use | Slab | Concrete | Mesh | Insulation under the slab |
|---|---|---|---|---|
| Garden room, no vehicles | 100 mm | C25/30 | A142 | 100 mm rigid floor insulation rated by its maker for use under a concrete slab (XPS, or a floor-grade EPS); 150 mm if the building is heated every day |
| Insulated garage, cars and storage | 150 mm | C30/37 | A193 | 100 mm XPS (≥300 kPa) or an equivalent rated for vehicle loads; 150 mm if the building is heated every day |
| Insulated garage, workshop, car lift or heavy equipment | 150 mm minimum; an engineer checks the lift posts, at extra cost | C32/40 | A252 | As for cars and storage |
| Any heated building of 50 m² or more | As above | As above | As above | Required by the Building Regulations energy-efficiency rules (Part L); building control confirms the thickness for your site |
Garden room, no vehicles
- Slab
- 100 mm
- Concrete
- C25/30
- Mesh
- A142
- Insulation under the slab
- 100 mm rigid floor insulation rated by its maker for use under a concrete slab (XPS, or a floor-grade EPS); 150 mm if the building is heated every day
Insulated garage, cars and storage
- Slab
- 150 mm
- Concrete
- C30/37
- Mesh
- A193
- Insulation under the slab
- 100 mm XPS (≥300 kPa) or an equivalent rated for vehicle loads; 150 mm if the building is heated every day
Insulated garage, workshop, car lift or heavy equipment
- Slab
- 150 mm minimum; an engineer checks the lift posts, at extra cost
- Concrete
- C32/40
- Mesh
- A252
- Insulation under the slab
- As for cars and storage
Any heated building of 50 m² or more
- Slab
- As above
- Concrete
- As above
- Mesh
- As above
- Insulation under the slab
- Required by the Building Regulations energy-efficiency rules (Part L); building control confirms the thickness for your site
Every base also gets
- Sub-base: 150 mm of compacted MOT Type 1, laid in layers (200 mm on clay or soft ground, or for vans and workshops), with sand blinding on top.
- Damp-proof membrane: A 1200-gauge damp-proof membrane, laps of at least 150 mm taped, turned up at the edges.
- Edges: Steel garages get a 150 mm thickened edge at the door threshold. Insulated slabs get perimeter edge insulation, with the edge detail to our installation drawing, sent with your order.
- Level: Dead level, with no fall across the slab.
- Cure: Allow at least 7 days for the concrete to cure before the building is installed.
Why we recommend an insulated base under insulated buildings
Our insulated garages and garden rooms have 100 mm PIR insulated walls and roof. A bare concrete slab loses heat several times faster per square metre than those walls, so on an insulated building the floor becomes the weak point — and a cold slab under a warm room is where condensation forms.
A garden room has no separate insulated floor. Its floor finish sits straight on the base — vinyl with Signature and Executive, or your own choice with Core — so the base is its only floor insulation.
The insulation goes under the slab, with a perimeter edge strip, so the concrete sits on the warm side.
It is not a Building Regulations requirement for most of our buildings. Energy-efficiency rules (Part L) do not apply to a stand-alone non-domestic building under 50 m². A heated building of 50 m² or more must meet them, which means an insulated floor. Building control confirms this for your site. (Building Regulations 2010, regulation 21)
See what's included with Steel Garages, Insulated Garages and Garden Rooms.
Garages carry more
Heavy-duty garage foundations
A garage foundation is not a garden-room foundation. Vehicles, multiple cars, SUVs and EVs, motorhomes, workshops, machinery and car lifts all put concentrated, moving loads through the slab — so the specification is heavier.
Designed for the way garages are used
Point loading under wheels and lifts, repeated turning loads, and the weight of stored vehicles and equipment are all designed into the slab thickness, reinforcement and sub-base.
Large garages (9×6 m · 30×20 ft and up)
Bigger footprints add considerations: differential settlement, expansion and shrinkage control, load distribution across the slab, edge reinforcement and turning loads. These are specified individually.
Three ways forward
Your foundation, your choice
However your base is handled, we confirm it works for your building before manufacture. Letting us manage it is the route we recommend.
I already have a suitable foundation
Have a level, sound base already? We check it is right for your building from the photos you send, then build straight onto it.
★ Recommended
VeltHaven Foundation Management
We manage the whole thing: site review, a foundation to our specification, a vetted groundwork contractor, project management, quality inspection and an installation-ready handover.
- Built to our specification
- Vetted UK groundwork contractor
- Project-managed, one company throughout
Guide price from your photos; firm quote after our contractor's visit
I'll use my own contractor
Prefer your own groundworker? We supply our specification and dimensions for your building so they can prepare the base to the correct standard.
If you prepare it yourself
Preparing the base yourself
If you or your contractor are preparing the base, this is a plain-English guide to the common methods and what each needs to get right — see also our free base-prep guide for a printable checklist. Site it on level, well-drained ground with clear access — away from large tree roots, overhead cables and underground services. Whichever method you use: dead level and square to the dimensions we give you, with no fall across the base and the ground around it draining away, a damp-proof membrane under any slab, and full curing time before installation.
Concrete pads / blocks
Suits: smaller, lighter buildings on firm, evenly-compacted ground.
Get right: precast blocks on a compacted base, giving point support under the corners and main load points. The ground must be firm and level — this is the least rigid method, so it settles if the ground moves.
Paving or slabs
Suits: a tidy, attractive base on firm, well-drained ground.
Get right: a compacted sub-base of hardcore or sand, topped with paving laid flat and dead level. It is only as stable as the sub-base and drainage beneath it — plan the drainage so water runs away from the building.
Reinforced concrete slab
Suits: most ground types, heavier buildings, and any building with our Showroom Finish resin floor.
Get right: a reinforced, dead-level pad sized to the building over a compacted sub-base, with a damp-proof membrane below. Allow at least 7 days to cure before installation, and set the position first — it is permanent.
Strip footing / foundation
Suits: larger or heavier garages, and softer ground that needs more support.
Get right: concrete poured into perimeter trenches carries the walls down onto firmer subsoil. It is the most groundwork of the four and permanent, so confirm the dimensions before you dig.
Unsure which suits your ground? Send your three site photos and we will advise the right base before you commit — or ask us to manage it for you.
Get the free base-prep checklist PDF
A six-step checklist, a labelled slab cross-section, the size-to-spec table and reference CAD links. One free guide, by email.
Guide pricing
Foundation Management — guide prices
These are guide prices for a fully managed foundation to our specification on a standard UK site. Your final price depends on ground conditions, access and the specification your site needs.
Your building is installed on a level, load-bearing base of the correct size. Providing that base is your responsibility and it is not included in the price. You can prepare it yourself, use your own contractor, or have VeltHaven Foundation Management design and build it for you: a guide price from your photos, then a firm quote after our contractor's site visit.
As a guide, Foundation Management, our fully managed service, costs from £5,095 to £6,295 for a garden-room base and from £5,495 to £8,695 for a garage base for cars and storage (125 mm slab), depending on size, ground conditions, levels and access. Built by your own groundworker, a base typically costs £1,900–£8,100 for a steel garage, £2,500–£10,800 for an insulated garage and £1,900–£5,600 for a garden room, excluding VAT. Add VAT if your contractor is VAT-registered.
If your own groundworker builds it — typical UK cost, excluding VAT
| Garage size | Steel garage, standard slab (excluding VAT) | Insulated garage, insulated slab (excluding VAT) |
|---|---|---|
| 4×6 m · 13×20 ft | £1,900–£3,600 | £2,500–£4,800 |
| 5×6 m · 16×20 ft | £2,400–£4,500 | £3,200–£6,000 |
| 6×6 m · 20×20 ft | £2,900–£5,400 | £3,800–£7,200 |
| 7×6 m · 23×20 ft | £3,400–£6,300 | £4,400–£8,400 |
| 9×6 m · 30×20 ft | £4,300–£8,100 | £5,700–£10,800 |
| Garden room | Insulated base (excluding VAT) |
|---|---|
| ATLAS — 5 × 4 m · 16 × 13 ft | £1,900–£3,700 |
| NOVA — 5 × 5 m · 16 × 16 ft | £2,400–£4,600 |
| APEX — 6 × 5 m · 20 × 16 ft | £2,900–£5,600 |
UK market rates, 2026, for the base specified above. Add VAT if your contractor is VAT-registered. Not included: a skip (£200–£350), a concrete pump (£200–£400 per half day), poor ground, slopes, restricted access, breaking out an old base.
Foundation Management — Garden Rooms
| ATLAS — 5 × 4 m · 16 × 13 ft (20 m²) | NOVA — 5 × 5 m · 16 × 16 ft (25 m²) | APEX — 6 × 5 m · 20 × 16 ft (up to 30 m²) |
|---|---|---|
| from £5,095 | from £5,395 | from £6,295 |
| Insulated base upgrade: +£1,600 | Insulated base upgrade: +£1,700 | Insulated base upgrade: +£1,900 |
Foundation Management — Garages, for cars and storage (125 mm slab)
| 4×6 m · 13×20 ft | 5×6 m · 16×20 ft | 6×6 m · 20×20 ft | 7×6 m · 23×20 ft | 9×6 m · 30×20 ft |
|---|---|---|---|---|
| from £5,495 | from £6,495 | from £6,795 | from £7,995 | from £8,695 |
| Insulated base upgrade: +£1,900 | Insulated base upgrade: +£2,200 | Insulated base upgrade: +£2,300 | Insulated base upgrade: +£2,800 | Insulated base upgrade: +£3,300 |
Insulated base upgrade — insulated garages and garden rooms: an extra cost on top of Foundation Management, from £1,600 to £3,300 depending on size.
Send us photos of the spot and we'll give you a guide price for the base. Once your deposit is paid, our contractor visits and gives you a firm quote before your balance is due. You can accept it, or lay your own base to our specification.
Guide prices are for a standard UK site with normal access. This does not affect your statutory rights.
The honest flow
How it fits your purchase
Order your building
Configure your building and pay your deposit online. Your order is confirmed.
Tell us about your base
After your deposit we ask for three site photos and whether your base is ready. Already prepared? Send photos of it. Planned? Tell us the type and date. Want us to handle it? Our contractor visits and gives you a firm Foundation Management quote before your balance is due.
Everything agreed before manufacture
Any foundation work and site extras are confirmed and agreed with you before we build anything.
Refundable until you pay the balance
Your deposit is fully refundable any time before you pay your balance. This does not affect your statutory rights.
Common questions
Groundwork FAQ
How thick should the concrete base be?
Our default is a 125 mm (100 mm absolute minimum) C25/30 slab for a steel garage used for cars and storage, a 150 mm C30/37 slab over insulation for an insulated garage, and a 100 mm C25/30 slab over insulation for a garden room, which carries no vehicles. For vans and 4x4s a steel-garage slab goes to 150 mm C30/37, and for a workshop or car lift to 150 mm minimum C32/40, where an engineer checks the lift posts, at extra cost. Every slab sits on 150 mm of compacted MOT Type 1 and a 1200-gauge damp-proof membrane. Allow at least 7 days for the concrete to cure before the building is installed. The exact thickness and reinforcement are confirmed for your ground and your load.
Do I need to insulate the base?
Under a steel garage you do not need to, unless you will heat a building of 50 m² or more. Under an insulated garage we recommend it, and under a garden room we strongly recommend it. Our insulated garages and garden rooms have 100 mm PIR walls and roof, and a bare concrete slab loses heat several times faster per square metre than those walls, so the floor becomes the weak point — and a cold slab under a warm room is where condensation forms. A garden room has no separate insulated floor: its floor finish sits straight on the base, so the base is its only floor insulation. Energy-efficiency rules (Part L) do not apply to a stand-alone non-domestic building under 50 m². A heated building of 50 m² or more must meet them, which means an insulated floor. Building control confirms this for your site.
Do I have to use VeltHaven for the foundation?
No. You can prepare the base yourself, use your own groundworks contractor, or ask us to manage it. If you use your own contractor we supply our specification and dimensions so it is built to the correct standard. Whichever route you choose, we confirm the base works for your building before manufacture.
How is my foundation decided?
It is specified individually — from your building weight and size, soil bearing capacity, drainage, frost protection, access and future loading. We advise the correct system after reviewing your site photos, rather than picking from a menu. If you choose Foundation Management, our contractor confirms it on the site visit.
Can I lay a base before ordering?
Yes — if you already have a sound, level base of the right size, we build straight onto it. Confirm the dimensions and specification with us before you pour or dig so nothing needs to be redone.
What does Foundation Management cost?
Guide prices for a fully managed foundation to our specification start at £5,095 for Garden Rooms and £5,495 for Garages (cars and storage, 125 mm slab) on a standard UK site. The base is not included in the building price. Your firm quote follows our contractor's site visit, once your deposit is paid, before you pay your balance. You can accept it, or lay your own base to our specification. This does not affect your statutory rights.
What if my site turns out to be non-standard?
Non-standard conditions are quoted from your three site photos after you place your deposit. We tell you the extra cost before manufacture begins. If you decide not to proceed, you get a full refund any time before you pay your balance. This does not affect your statutory rights.
Does the foundation affect planning permission?
The base itself does not normally require separate planning permission in England and Wales. The building above it may require a permitted development check or a full application depending on size and siting — the configurator provides guidance for each product. If you are unsure, consult your local planning authority.
Ready to move forward?
Plan your build
Configure your building and get a live price in minutes. Or talk to us about your site and we will guide you through the foundation options.