Engineered site preparation
Foundation & Groundwork
Your building deserves more than a concrete slab. It deserves an engineered foundation designed to protect your investment for decades — the right base for your ground, your building and how you use it.
The base is not included in the build price. You can prepare it yourself, use your own contractor, or let us manage the whole thing — whichever suits you. See our Delivery & Installation terms.
What's in the build price
Included as standard
Every VeltHaven building price includes VAT, delivery to your address and full professional installation. There are no hidden charges on standard sites.
Included in every build
- VAT, 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 engineered 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 before you commit.
The engineered option
The VeltHaven Engineered Reinforced Foundation
Where a reinforced foundation is specified, these are the typical specifications — confirmed for your project after the site review. Nothing here is a blanket promise; the engineering specification for your ground is what governs.
Typical specification
- Structural concrete, typically C30/37–C35/45
- Slab depth typically 150–300 mm to the engineering spec
- Steel mesh reinforcement; edge beams where required
- Compacted MOT Type 1 sub-base over geotextile
- Damp-proof membrane and expansion joints
- Laser-level finish to a defined tolerance
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 laser-level finish is what lets doors and sliding walls run true for years.
At this level of investment, the engineering detail is the point — a level, dry, correctly-loaded base is what protects the building.
Budgeting your groundwork
What size building needs what base? (typical UK guidance)
Base requirements scale with the building's weight and how you'll use it. The figures below are typical UK industry guidance for domestic garages and garden rooms — useful for budgeting your groundwork and for sense-checking any quote you get.
| Building & use | Typical slab | Typical concrete | Reinforcement | Notes |
|---|---|---|---|---|
| Garden room under 10 m² | 100mm | C25/30 | Mesh optional | Smaller rooms can also sit on pad/slab systems on firm ground |
| Garden room 10–20 m² (e.g. a 5×4m office) | 100mm | C25/30 | A142 mesh advised | Mesh is strongly advised above 10 m² |
| Garden room over 20 m² (e.g. 5×5m and up) | 125–150mm | C25/30–C30/37 | A142–A193 mesh | Heavier builds and furniture loads justify the step up |
| Single garage, car + storage | 100mm minimum | C25/30 | A142 mesh | Never below 100mm — thin slabs crack within a few years under vehicle loads |
| Double garage, or vans / 4x4s | 150mm | C30/37 | A193 mesh | Heavier and repeated vehicle loads |
| Workshop use, car lift, heavy equipment | 150mm minimum | C30/37 | A193 mesh | Treat as the floor of a working building, not a parking pad |
Garden room under 10 m²
- Typical slab
- 100mm
- Typical concrete
- C25/30
- Reinforcement
- Mesh optional
Smaller rooms can also sit on pad/slab systems on firm ground
Garden room 10–20 m² (e.g. a 5×4m office)
- Typical slab
- 100mm
- Typical concrete
- C25/30
- Reinforcement
- A142 mesh advised
Mesh is strongly advised above 10 m²
Garden room over 20 m² (e.g. 5×5m and up)
- Typical slab
- 125–150mm
- Typical concrete
- C25/30–C30/37
- Reinforcement
- A142–A193 mesh
Heavier builds and furniture loads justify the step up
Single garage, car + storage
- Typical slab
- 100mm minimum
- Typical concrete
- C25/30
- Reinforcement
- A142 mesh
Never below 100mm — thin slabs crack within a few years under vehicle loads
Double garage, or vans / 4x4s
- Typical slab
- 150mm
- Typical concrete
- C30/37
- Reinforcement
- A193 mesh
Heavier and repeated vehicle loads
Workshop use, car lift, heavy equipment
- Typical slab
- 150mm minimum
- Typical concrete
- C30/37
- Reinforcement
- A193 mesh
Treat as the floor of a working building, not a parking pad
- The door threshold is the weakest point. The front edge takes vehicle loading, frost and edge impact every day — typical guidance is 150mm at the threshold and edges even where the centre of the slab is thinner.
- The slab is a system, not a pour. Under the concrete: 100–150mm of compacted MOT Type 1 sub-base and a damp-proof membrane. The membrane is what keeps ground moisture out of your building for the next few decades — it's not optional.
- Concrete needs to cure. Allow at least 7 days before the building goes up on a fresh slab.
How VeltHaven's spec compares
Our own base specification — C30/37–C35/45 structural concrete at 150–300mm depending on the building and site, over MOT Type 1 and a geotextile layer, with steel mesh reinforcement — sits deliberately at or above the top of these industry ranges. We'd rather your base outlives the building's warranty several times over than meet a minimum.
Every site is different, though — soil, slope and access all matter — which is why your exact base requirement is confirmed as part of your order, from the site photos you send after checkout, before anything is manufactured. If your existing base already meets the spec for your building, we'll tell you that too.
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 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. Most customers choose to let us manage it.
I already have a suitable foundation
Have a level, sound base already? We confirm it is right for your building from your site photos, then build straight onto it.
★ Recommended
VeltHaven Foundation Management
We manage the whole thing: site review, an engineer-specified foundation for your ground, a vetted groundwork contractor, project management, quality inspection and an installation-ready handover.
- Engineer-specified for your site
- Vetted UK groundwork contractor
- Project-managed, one company throughout
Quoted after your site review — agreed before manufacture, or your deposit is refunded.
I'll use my own contractor
Prefer your own groundworker? We supply the engineering drawings and technical specification 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. 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, a fall for drainage, 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 a fall 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 5–7 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.
Guide pricing
Foundation Management — guide prices
These are guide prices for a fully managed, engineer-specified foundation on a standard UK site. Your final price depends on ground conditions, access and the specification your site needs.
Garden Rooms
| 4×6 m | 5×6 m | 6×5 m | 6×6 m |
|---|---|---|---|
| from £6,495 | from £7,495 | from £8,995 | from £9,995 |
Garages
| 6×6 m | 7×6 m | 8×6 m | 9×6 m |
|---|---|---|---|
| from £9,995 | from £9,995 | from £10,995 | from £11,995 |
Final quotation issued after your site review — agreed before manufacture, or your deposit is refunded. 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? We issue the engineering-reviewed Foundation Management quote.
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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
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 the engineering 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.
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, engineer-specified foundation start at £6,495 for Garden Rooms and £9,995 for Garages on a standard UK site. Your final quotation is issued after your site review and agreed before manufacture — or your deposit is refunded. 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.