Nearly every page on this site ends with an invitation to request a site survey, and almost nobody explains what that involves. It is a reasonable thing to be cautious about: for most people, “we will send someone round” means a salesperson.
It is not that. A survey is the measuring exercise that makes it possible to design anything at all, and without it a quotation is arithmetic performed on a guess.
Why a photograph is not enough
People often ask whether a quotation can be produced from photographs and a rough size. For a broad indication, sometimes. For a number you could sign, no - and it is worth knowing exactly what is missing.
None of the following is visible in a photograph, and every one of them changes either the structure or the price:
- Levels. Ground that looks flat rarely is. Fall across a site changes column lengths and decides which way water runs.
- What is underground. A water line, a cable, a septic run or a foundation from something demolished years ago. Footings have to avoid all of them.
- The soil. It sizes the foundations, and the foundations on a tensile structure are resisting uplift rather than bearing weight.
- Access. Whether a truck and a small crane can reach the spot, or whether every component is carried in by hand.
- Where water can go. There has to be an existing drain, or somewhere sensible to discharge to, and it has to be somewhere nobody walks.
- The obstructions nobody mentions. The gate swing, the tree, the neighbour's window, the overhead line.
A number produced without those is not a quotation. It is a placeholder, and placeholders move upward.
What actually happens on the visit
In roughly this order, though sites rarely cooperate with an order:
- Understanding what you want covered, and why. This shapes more than people expect. Shade from afternoon sun, shelter from rain, and a covered route between two doors are three different structures over the same footprint.
- Measuring the space. Dimensions, levels, and the fixed points the design has to work around.
- Working out where columns can land. Usually the single most constraining question, and the one that decides the form — cantilever, free-standing, or fixed back to the building.
- Checking what is underground and overhead. Services, and anything the structure or a crane has to clear.
- Looking at drainage. Where water will leave the roof and where it can go afterwards.
- Access and sequencing. How material arrives, where it can be set down, and whether the space has to stay in use during the work.
If the space has to keep working — a car park that cannot close, a courtyard in a live building — say so during the survey rather than later. It changes how the job is sequenced, and it is much cheaper to plan for than to retrofit.
What to have ready
None of this is essential, and all of it makes the visit shorter and the design better:
- Any drawings you have — site plan, elevation, services layout. Even an old or partial one helps.
- Rough dimensions, if there are no drawings at all.
- Photographs from a few angles, taken beforehand.
- Whether a society, RWA or local authority has to approve it, and whether there is a standard design everyone follows.
- Any constraint you already know about — a wall that cannot be touched, a date the space must be free, a colour the building uses.
What you get afterwards
A design direction for the space, and an itemised quotation against it.
The itemisation is the part that matters. A single figure tells you nothing and cannot be compared with anyone else's single figure. An itemised quotation shows the steel, the membrane, the foundations, the drainage and what is excluded — which is what makes two quotations comparable at all. Ten questions to ask before you sign →
It should also give you a programme in stages rather than a single completion date. How long a tensile structure takes →
And if you decide not to go ahead
Then you have accurate measurements of your space, a view on where columns can and cannot go, and an itemised figure to compare with anyone else's. That is a reasonable outcome for an hour of your time, and it is why the survey is free: it is the only way either side finds out whether the project is worth doing.