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Spatial Dimensions is a UK measured building survey and geospatial company providing site mark outs — the physical marking of detected underground utilities on the ground before excavation — from permanent offices in London, Sevenoaks and Nottingham, working on site anywhere in the UK.
In short: a site mark out from Spatial Dimensions puts clear, colour-coded paint marks on the ground showing the position — and on hard surfaces, the recorded depth — of buried electricity, gas, water, telecoms and drainage lines detected by electromagnetic location (EML) and ground penetrating radar (GPR). Temporary biodegradable paint is the standard, applied by CSCS-carded surveyors under a site-specific risk assessment. A mark out is the quickest way to make an imminent excavation safer, and we will tell you plainly when you need a full mapped utility survey instead. Mark outs start at £700 per day on site.
or call 01732 458799
What is a site mark out?
A site mark out is the process of physically marking the location of detected underground utilities on the ground surface before excavation or construction begins. Spatial Dimensions surveyors sweep the dig area with EML and GPR, interpret the signals on site, and paint each detected service onto the surface where the excavation team will work.
The Health and Safety Executive’s guidance HSG47, Avoiding Danger from Underground Services, expects buried services to be located and marked before anyone breaks ground. A mark out is how that is met on the day: the crew digs from marks under their feet, not from a drawing pinned up in the site cabin.
What are the marks made of, and how long do they last?
Swipe the table sideways to see all the columns.
| Marking material | When Spatial Dimensions uses it |
|---|---|
| Biodegradable temporary spray paint | The standard. Survey grids, detected services, chamber extents and, on hard surfaces, recorded depths. Weathers away without permanently staining drives, paving or roads |
| Long-lasting survey spray paint | On request, where the site is damp or the marks must survive until a later dig date. Ask before work starts — we cannot switch paints once marking is under way |
| Tape, chalk or marker flags | Sensitive surfaces — heritage paving, decorative landscaping, interior floors. Tell us about surface restrictions at enquiry |
How long the marks stay legible depends on weather and site traffic, and Spatial Dimensions is honest about that: marks fade faster in wet conditions. If your site is damp, or the marks must survive until a later dig date, say so before work starts.
One thing to know in advance: we do not remove the marks after the survey. The standard paint fades on its own; if marks need to go sooner, ask us and we will help.
Do I get a drawing, or just marks on the ground?
A mark out on its own gives you marks on the ground, not a drawing — and that difference matters. Paint is temporary; a drawing is a permanent record. Once the marks fade, the information is gone.
A mark out alone suits one situation well: excavation that is about to happen, by a team on site now. If the utility information is needed for design, planning or anything you will refer back to later, commission a full underground utility survey, where the same detection is recorded against a topographical survey base and delivered as a PAS 128-compliant CAD drawing or 3D model.
Every Spatial Dimensions detection survey marks its findings on the ground as fieldwork proceeds — a mark out is that fieldwork commissioned as the end product. If you are unsure which you need, tell us what the data is for and we will recommend honestly.
Can I dig as soon as the site is marked?
Yes, but treat the marks as guidance, not a guarantee. Detection technology has limits, and Spatial Dimensions would rather you knew them before the excavator arrives.
- A utility survey can locate up to about 95% of buried services — 100% detection is not feasible, and small-diameter fibre laid directly in the ground is likely undetectable.
- Depth tolerances: with EML and GPR used together, expect ±15% of the recorded depth; a single method alone is ±40%.
- Services within 25 cm of a surface obstruction — walls, fences, skips, parked vehicles — may go undetected, and reinforcing grids in concrete impair GPR penetration.
Follow HSG47 safe digging practice: dig trial holes carefully by hand to positively confirm a service’s position and depth before machine excavation near it. Where a service is critical — a high-voltage cable, a gas main, anything you cannot afford to strike — specify a PAS 128 QL-A utility verification survey, where vacuum excavation exposes the service and confirms exactly where it is.
What happens on site during a mark out?
Spatial Dimensions issues a site-specific risk assessment and method statement (RAMS) before mobilising. Our field surveyors carry CSCS cards and DBS/BPSS clearance, and the company holds £10 million each of professional indemnity, public liability and employers liability insurance.
On the day, the team sweeps the area with EML and GPR and paints up findings as the work proceeds. Inspection covers are lifted with a hand-operated hydraulic lifter — 30 minutes maximum per cover, with anything that will not lift safely recorded as Unable to Lift. On minor public roads we provide basic signing, lighting and guarding to Chapter 8 of the New Roads and Street Works Act; strategic roads need third-party traffic management, arranged at cost.
You can help: clear what obstructions you can and cut long grass short before we arrive — GPR reads a uniform surface far better, and return visits caused by obstructions are chargeable.
Who commissions a site mark out?
Mostly groundworks contractors and site managers with an excavation imminent — the people who will be in the trench. Mark outs also run within the larger underground utility surveys Spatial Dimensions has delivered at sites including Hinchingbrooke Hospital, William Harvey Hospital and Broadwalk House.
We mobilise in an average of 5.3 working days from instruction; if your programme is tighter, say so at enquiry. If you are a contractor, our resources page for contractors explains how survey information fits your programme.
How much does a site mark out cost?
Site mark outs from Spatial Dimensions start at £700 per day on site. Most site mark outs fall between £850 and £1,000, depending on the size of the area and the density of services.
Price depends on the size of the area to be marked, the expected density of services, the number of covers to lift, the surface types and whether traffic management is needed. Spatial Dimensions quotes a fixed price against a written specification, so you know the cost before we mobilise.
For a fixed price, send us the site address and what needs marking. We will come back with a written quote within 24 hours. All prices exclude VAT.
If you are comparing quotes, the Spatial Dimensions Survey Buyers Guide — free to download from our guides page — lists ten checks that separate a good survey from a cheap one.
or call 01732 458799.
Frequently asked questions
As standard Spatial Dimensions uses temporary biodegradable spray paint, which weathers away without permanently staining hard surfaces. For sensitive surfaces we can use tape, chalk or marker flags instead — tell us at enquiry stage.
There is no fixed lifespan — it depends on weather and site traffic, and marks fade faster in wet conditions. If the marks must last until a later dig date, ask for long-lasting survey spray paint before work starts.
No. Marks are not removed after the survey — the standard biodegradable paint fades naturally. If you need them gone sooner, ask us and we will help.
You can start, but dig carefully. Marks show detected services to stated tolerances (±15% depth with dual-technology detection), around 95% of services at best, and features close to obstructions can be missed. Hand-dig trial holes to confirm position and depth before machine excavation, as HSG47 recommends.
Only if you commission a mapped survey. A mark out delivers marks on the ground; a full underground utility survey records the same findings on a topographical base as a permanent CAD or 3D deliverable.
Request a site mark out quote
Send us the site address, the area that needs marking and your dig date; Spatial Dimensions will reply with a written, fixed-price quote within 24 hours.
Email: website@spatial-dimensions.co.uk
Phone: 01732 458799
Offices: London · Sevenoaks · Nottingham · working nationwide
Related services
- Underground utility surveys — the mapped survey and parent service
- Electromagnetic location surveys — one half of the detection behind a mark out
- GPR surveys — the other half
- PAS 128 surveys — quality levels and what each one means
- Utility verification surveys — QL-A trial holes where a strike is unaffordable
- Topographical surveys — the base a mapped utility survey is drawn on
