Site Readiness & Installation
Modular building foundations: check before groundworks
Agree what supports the building before you order what goes in the ground. Check the drawings, site information and responsibilities first.
- Start with
- Building and site information
- Resolve
- Support, levels and scope
- Do not assume
- One base suits every unit
What foundations does a modular building need?
Modular building foundations must suit the building’s support requirements and the conditions beneath it. There is no universal pad count, slab thickness or foundation type. Start with the supplier’s support layout and design loads, then have the appointed designer assess the ground and foundation arrangement. An existing concrete yard is not proof of suitability, and a temporary building still needs an appropriate support solution. Coordinate finished levels, drainage, services and entrances before construction. For a useful first discussion with KC, send your intended use, approximate layout, site postcode and any surveys or existing-base records. Mark unknowns rather than guessing.
Who this guide is for
- Facilities and estates teamsConsidering a new building on an existing site.
- Contractors and project managersCoordinating the building supplier and groundworks package.
- Business ownersChecking whether an available yard or base can be used.
- Procurement teamsComparing proposals with different site-work exclusions.
Start with the situation on your site
Use this table to frame the enquiry, not to select a foundation without design input. The building route remains important: review KC’s modular building options alongside the site constraints.
| Situation | What to check | Why it matters | Next step |
|---|---|---|---|
| Existing concrete yard | Construction records, condition and the proposed loading. | Appearance does not establish suitability. | Arrange an engineering assessment. |
| Ground conditions unknown | Site history and the investigation needed. | A foundation proposal needs an evidence basis. | Ask the designer what information is missing. |
| Linked or stacked units | Current support layout and reactions for that configuration. | Do not copy another building’s base arrangement. | Agree the supplier’s drawing revision. |
| Tight access or sloping site | Levels, entrances, services and installation space. | The building footprint is only part of the site brief. | Provide a site plan and level information. |
On a small screen, scroll the table sideways. Keyboard users can focus the table area.
Modular building foundations start with the support drawing
The external dimensions tell you where the building fits. They do not tell you where it must be supported. Different modular structures can transfer loads through walls, edge beams or posts. Steel Construction Info’s technical guide to modular construction describes these differences and the importance of the foundation interface.
Ask for the current support layout and a schedule of reactions: the forces delivered to the supports. The engineer should confirm the loading basis, directions and relevant design cases. Do not turn a transport weight into foundation loads by simply dividing it equally between the corners.
Modular building point loads are only one design input
Have the building supplier and foundation designer agree what is needed: support coordinates, levels, connection details, design loads and movement tolerances. Keep the document status clear—preliminary, for pricing or issued for construction—and withdraw superseded revisions. The same approach applies to portable cabin foundations: use the proposed unit’s requirements, not a base copied from another project.
For England, Approved Document A covers structural loading and elements including foundations. It is guidance, not confirmation that a particular proposed base is suitable.
Can you use an existing concrete base?
Possibly, but keep reuse as an option to be assessed rather than a saving already secured. Give the engineer the original drawings, any reinforcement and thickness records, known repairs, previous use and available ground information. They should decide whether inspection, testing or further investigation is required.
Ask for a written conclusion for the proposed building, including any alterations or restrictions. An old slab, a paved yard and a designed building foundation are not interchangeable descriptions.
An illustrative change of building
A site owner removes a small cabin and proposes a larger linked office on the same area. The earlier cabin’s base records can help the assessment, but they do not prove that the new support locations and loads are acceptable. No dimensions, costs or outcome are assumed in this example.
Do not investigate by digging first
Arrange the investigation through competent people. HSE’s excavation guidance addresses ground information, services and the risk of undermining nearby structures. Intrusive work needs its own safety planning.
Compare foundation routes after the site review
These are routes to discuss with the designers, not a product recommendation or a statement that every option is available with every KC system.
| Proposed route | Ask the design team | Do not assume |
|---|---|---|
| Concrete pads | How are pad positions, dimensions and connections established? | A standard pad size or a fixed number per module. |
| Strips, ground beams or a raft | How does the arrangement match the building’s support needs? | Any continuous concrete base supports every system. |
| Piles, including a proposed screw-pile system | What investigation, verification and connection design are required? | A fast installation method removes the need for design. |
| Proprietary removable supports | What site preparation, bearing checks and installation evidence are needed? | Removable means suitable on unverified ground. |
The range of foundation interfaces is discussed in the technical guide linked above. Suitability and the final specification remain project-specific.
Have a building location, but not a foundation design?
Send the layout, postcode and information already available. Start a modular-building enquiry so the unresolved site requirements can be identified.
An initial project review is not a foundation design or a booked site inspection.
Resolve levels, drainage and entrances together
Ask for a coordinated drawing showing finished floor level, external ground levels, thresholds, service entries and drainage connections. Give the site team one agreed reference level and identify who checks the completed works against it.
Discuss paths, ramps or landings before the base is fixed. For non-domestic projects in England, Approved Document M Volume 2 provides access guidance. A door specification alone does not resolve the approach to the building.
Ask the designers to coordinate moisture protection and drainage with the support arrangement. Approved Document C covers site preparation, contaminants, sub-soil drainage and resistance to moisture in England. Do not select details from a photograph of a finished building.
Make the boundary between supplier and site work explicit
Use the enquiry and appointments to name who provides each item. This is a coordination checklist, not a substitute for the parties’ contractual or statutory responsibilities.
- Building information: who supplies the support layout, reactions, connection requirements and revisions?
- Site and foundation design: who interprets the ground information and designs the proposed solution?
- Interfaces: who coordinates levels, drainage, access works and service positions?
- Construction: who sets out, builds and records the foundation works?
- Readiness: who checks the agreed tolerances, required records and release for installation?
Ask for the inspection and evidence requirements before work is covered up. Where concrete or another material has a strength requirement before loading, the designer should define the acceptance basis; do not use a generic waiting period from an online article.
Check the work area as well as the building position
Before excavation, the contractor needs a safe system of work. HSE’s HSG47 guidance separates planning, locating and identifying buried services, and safe excavation. Existing plans are part of the information pack, not permission to dig.
Keep lifting access separate from the foundation acceptance. Suitability for the building does not, by itself, establish suitability for delivery vehicles or crane outriggers. The lifting team must assess its own operation and ground conditions; see HSE’s lifting-operation planning guidance.
For the wider sequence, use KC’s delivery and installation checklist. Keep vehicle routes, unloading areas and required working space on the site plan.
Compare modular building groundworks costs
Ask each contractor to price the same drawing revision. Separate investigation, design, site preparation, excavation, spoil handling, foundations, service provisions, external works and completion records. Identify allowances and work by others.
Check VAT, quotation validity, exclusions and the process for changed ground conditions. A low foundation price is not comparable with a wider groundworks package until the missing items are identified. No standard price or saving is assumed here.
Confirm the approval route before committing to work
Building Regulations approval and planning permission are separate processes; a project may need both. Do not infer an exemption from the words “portable”, “temporary” or “removable”.
The Approved Document references in this guide concern England. Check the applicable national guidance and project route: Wales has its own Approved Documents, while Scotland and Northern Ireland have separate systems.
What KC needs to review your building enquiry
For a site in Stoke-on-Trent, elsewhere in Staffordshire or another UK location, start with the actual postcode and proposed building position. Send what is known and flag gaps.
- Use and layout: intended activities, approximate size, occupancy and room schedule.
- Duration: temporary or permanent requirement, including any planned relocation.
- Site information: postcode, marked-up site plan, photographs and level survey if available.
- Existing base: drawings, previous use, inspection reports and known alterations.
- Groundworks status: surveys, ground reports, design appointments and any contractor already involved.
- Access: delivery restrictions, working space, overhead constraints and site operating rules.
- Services: known utility routes, proposed connections and drainage information.
- Programme and approvals: target occupation date and the current planning or building-control position.
- Finish and budget: building appearance, entrance expectations and budget direction where available.
KC’s first review can identify likely system fit and information gaps. It does not replace the foundation designer’s assessment or confirm that site works are included in the building price.
Modular building foundations: common questions
Do modular buildings need foundations?
They need a suitable, designed means of support, but that does not always mean a full concrete slab. The arrangement depends on the building system and the site. Ask the supplier for the support requirements and ask the appointed foundation designer to check the ground and proposed solution together. A temporary or relocatable label is not evidence that the building can be placed directly on any available surface. Treat foundations, anchorage and installation conditions as part of the project review.
Can a modular building go on an existing concrete base?
Possibly, but an existing base should not be accepted just because it looks sound. Give the engineer any drawings, construction records and information about its previous use. They can determine what inspection or investigation is needed for the new support positions and loads. The outcome may be reuse, local alterations, a separate foundation arrangement or replacement. Keep the decision open until the assessment is complete, and do not book delivery on the assumption that visual condition proves suitability.
How are concrete pads for modular buildings specified?
There is no reliable universal number. The required supports depend on how the particular building transfers its loads, including its configuration and any linked or stacked units. Ask for the supplier’s current support layout and the designer’s foundation details for that arrangement. A sketch showing four corners is not a substitute. Changes to the building can require the support information to be reviewed, so agree the drawing revision before the groundworks contractor starts setting out.
Are ground screws suitable for modular buildings?
They may be an option where a specialist design demonstrates suitability for the ground, building loads and connection details. Ask what investigation, capacity verification, installation records and durability information the proposal requires. Do not choose a screw foundation solely because its installation is described as quick or removable. The modular supplier, foundation designer and installer need to agree the interface. Also confirm underground constraints and whether the proposed system is compatible with the selected building; availability is not assumed here.
How much do modular building foundations cost?
A useful price needs a defined building and a site-specific groundworks scope. Ask whether the offer includes investigation, engineering, setting out, excavation, spoil handling, foundations, service provisions, external levels and completion records. Separate confirmed work from allowances, exclusions and items by others. Compare the same drawing revision and VAT basis. This guide does not give a standard price per pad or per square metre because those figures would conceal the differences the quotation needs to resolve.
Who is responsible for the foundations and when should work start?
Responsibility depends on the appointments and agreed contract scope. Before work starts, identify who supplies the building support information, designs the foundations, coordinates the site interfaces, constructs the works and checks readiness for installation. Record the required drawings, investigations, permissions and inspections for the stage being released. Do not assume that ordering a building also commissions foundation design or groundworks. Send KC your available project information so the building enquiry can identify these scope questions early.
Your next step
Plan the building and its site together.
Send your use, approximate layout and site postcode. Include existing-base records or surveys where available so KC can identify the information needed for a project-specific building quotation.