External works sit in an awkward spot on most property budgets. They are too small to attract the scrutiny a building project gets, and too large to sign off casually. A car park resurfacing, a courtyard rebuild, a set of retaining walls at a distribution site: these routinely run to six figures, and they are frequently procured on the strength of three emailed prices and a site walk.
That is where the overruns come from. Not from bad contractors, in most cases, but from a specification thin enough that every bidder priced a different job.
The checks below apply whether you are a facilities manager with a portfolio of sites, a developer handing over a residential scheme, or a business owner dealing with the grounds around a single building. They also apply regardless of where the site sits. Published guidance on choosing the right landscaping company in Glasgow lists broadly the same criteria a London property team would use, because the risks in external works are structural rather than regional.
Write the specification before you ask for prices
If you send out a sketch and a rough description, you will get back numbers that cannot be compared.
A usable specification for external works needs the buildup for every surface, stated in millimetres of sub-base and bedding, along with the product, thickness and finish. It needs falls and drainage strategy. It needs edge details, because edges are where cheap work fails first. It needs a planting schedule with species, pot sizes and quantities if soft works are included. And it needs the boundaries of the contract written down, so that everyone knows whether the contractor is responsible for the tarmac up to the kerb line or the whole approach.
Without that, you are not running a tender. You are collecting guesses.
If you do not have the technical capacity in house, engaging a designer or a quantity surveyor for the specification stage typically costs a fraction of the variations you will otherwise absorb during the build. The Royal Institution of Chartered Surveyors maintains professional standards and a member directory for exactly this kind of appointment, and the RICS site is the place to verify that whoever you engage is regulated.
Understand your duties as a commercial client
This is the part most buyers get wrong, and it carries legal weight.
Under the Construction (Design and Management) Regulations 2015, a commercial client has duties on construction projects, and hard external works count. Where more than one contractor will be involved, you must appoint a principal designer and a principal contractor in writing. You must make sure a construction phase plan is in place before work starts. You must provide pre-construction information about the site, including anything you know about buried services, contamination or asbestos in existing structures.
Projects also become notifiable to the Health and Safety Executive when construction work lasts longer than 30 working days and has more than 20 workers on site at the same time, or exceeds 500 person days. A large external works package can cross that threshold without anyone realising, particularly on a phased site. The HSE sets out the client duties in plain terms and the guidance is worth reading before you issue a tender rather than after.
Delegating these duties to the contractor by email does not discharge them. If something goes wrong on your site, the question of whether you fulfilled your client duties will be asked.
Check financial standing before technical capability
A contractor who cannot pay their suppliers will not finish your job, however good their portfolio looks.
Pull the filed accounts at Companies House. Look at the age of the entity, whether accounts are filed on time, and whether there is a pattern of the company being dissolved and reincorporated under a similar name. Check the net asset position. A firm with negative reserves taking on a contract worth more than its annual turnover is a risk you are underwriting whether you intend to or not.
Then ask for two trade references from material suppliers rather than from clients. Suppliers know within a fortnight when a contractor stops paying. Clients often do not find out for months.
Insurance next. Ask for the certificate, not a statement that they are covered. Check the public liability limit, which should sit at five million or above for anyone operating a plant near occupied buildings. Check employer’s liability, which is a legal requirement for anyone with employees. Check the expiry date, and diarise it if the contract runs past renewal.
What to look for in the returns
When the prices come back, resist the urge to compare the totals first. Compare the assumptions.
Here is what usually separates a considered bid from a thin one:
- Excavation volumes and disposal costs stated separately, with the assumed material classification
- A named product and supplier for every surface rather than a generic description
- Drainage design included, with the discharge point identified
- Access and plant strategy explained, including what happens if the site is occupied during the works
- A programme showing sequence and duration rather than a bare start date
- Provisional sums flagged and explained rather than buried
- Exclusions listed in full
The last item tells you most. A bid with no exclusions is rarely comprehensive. It is usually a bid where the exclusions have not been thought through, and they will arrive later as variations.
Be sceptical of the lowest number by a wide margin. On external works, a bid that comes in 35 per cent under the others has usually missed something structural, most often the sub-base depth, the drainage, or the ground conditions. You will pay the difference eventually, and you will pay it at variation rates rather than tender rates.
Get the contract right as well as the price
For anything above roughly fifty thousand pounds, use a recognised standard form rather than the contractor’s own terms or an exchange of emails.
The contract should set out payment stages tied to measurable completion rather than to calendar dates, a retention percentage held until the defects period expires, a defined defects liability period, liquidated damages for late completion, and a clear variation procedure requiring written instruction before additional work proceeds.
Retention matters more on external works than people expect. Paving settles. Drainage reveals itself in the first heavy rainfall. Planting either establishes or it does not. Holding five per cent for twelve months gives you a bargaining position at precisely the point when problems appear, and twelve months covers a full weather cycle.
Payment terms are also now a matter of public record for larger businesses, since firms above the reporting threshold must publish their payment performance twice a year. If you are appointing a contractor, they can check yours as easily as you can check theirs.
Assess the team, not the portfolio
Photographs prove that a company completed a project once. They do not prove that the same people are still there.
Ask who will be on site. Ask whether they are employed or subcontracted, and if subcontracted, whether the same subcontractors have worked with the firm before. Ask who the site supervisor will be and whether they hold a relevant qualification. Ask what happens if that person leaves mid contract.
Then ask for a reference from a project completed three or more years ago, and visit it if you can. Recent work photographs well. Work that has been through several winters, several freeze cycles and several thousand vehicle movements is the only meaningful test of whether the groundwork was done properly.
Accreditation gives you a shortcut here. Health and safety schemes such as SafeContractor and SMAS, along with ISO 9001 and ISO 45001 certification, mean an independent assessor has reviewed the firm’s systems. That is not a guarantee of quality, but it does tell you the business documents what it does rather than improvising.
Spend the time at the front of the process. Every hour you put into the specification and the checks saves several during the build, and the money you save is the money you would otherwise spend on variations nobody planned for.
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