Who this guide is for
- Self-builders and owners assessing a plot before a method of construction is chosen
- Readers building on a terraced, urban or otherwise enclosed site
- Anyone considering panelised, modular or precast construction
- Owners inserting new structure inside an existing occupied building
- Buyers comparing two plots where one has a working access and the other does not
The pieces get bigger as the site work gets smaller
The trade that manufactured construction offers is fewer operations on site in exchange for larger pieces arriving complete. That trade is only available if the pieces can reach their position. Precast units are heavy, arrive in sequence and cannot be trimmed; mass timber panels are craned into position and cannot be trimmed to fit; volumetric units arrive as complete enclosures.
Small-unit construction makes the opposite trade. More is done in place, the largest single item is smaller, and the access requirement falls accordingly. Neither is better; they are answers to different sites.
Delivery order is part of the design, not the logistics
The precast entry makes a point that surprises people: crane position, delivery order and access govern the design as much as the plan does, and a unit that arrives out of sequence occupies space that the next one needs. Mass timber says the same in different words, adding that a change agreed on site may have already been manufactured somewhere else.
On a site with room to lay things down, an out-of-sequence delivery is an inconvenience. On a site with none, it is a stoppage, because there is nowhere for the piece to wait.
- Whether anything can be laid down on site at all, and where
- Whether a vehicle can wait, turn, or must reverse the whole route
- Whether a lift can be made from one position or the machine has to move
- What happens when a delivery arrives in the wrong order
Where the lift is made from is a plan constraint
A lifting position is not just somewhere for a machine to stand. It has to reach every position a piece has to go, from ground that can carry it, without the building it is erecting getting in the way of the next lift. That interacts with the erection sequence, which interacts with the structural arrangement.
Which is why the published entries treat it as a design question. If the arrangement cannot be erected from the position available, the arrangement changes, and that change is cheapest before anything is fabricated.
Inside an existing building the constraint is the same, in miniature
The mezzanine entry describes an insertion into a building that already exists and is often still in use, and states that access for members, the room needed to lift them and the sequence in which the space can be released all shape the arrangement well before any preference about materials does.
That is the clearest statement of the principle in the whole library. What can be got in, and how, comes before what would be preferred, and a member that cannot be brought through the building is not a member that can be used however well it performs.
The first course, the first row, the base
Access also determines how carefully the start can be set out, and the start propagates. In insulating formwork the accuracy of the base course propagates upward through everything that follows. In precast the question is how the first lift is levelled and set out, given that everything above inherits it. In modular work the accuracy of the plane the first row stands on propagates through the whole stack.
A cramped site makes that first setting-out harder, which is a quieter cost than a blocked delivery but a more expensive one, because it is inherited rather than absorbed.
Scaffolding, storage and the space that is not there
Access is not only the route in. The same constrained site has to find room for scaffolding, for storing material that has arrived but is not yet needed, for waste leaving, for welfare and for the trades' own vehicles. Each of those competes with the others and with the delivery route itself.
Where they cannot coexist, the sequence has to separate them in time instead, which lengthens the programme. That is worth knowing at the point of choosing the method rather than at the point of building to it.
- Scaffolding, and whether it can stand where it needs to
- Storage for material that arrives before it is needed
- Waste and spoil leaving the site
- Parking, welfare and the trades' own access
The neighbours are part of the access
On an enclosed plot the route in frequently runs along, over or beside somebody else's property, and the arrangements for that are separate from the technical question and run to their own timetable. Establishing early whether a shared access, a right of way or a neighbouring structure is involved is worth doing because those processes cannot be compressed at the end.
The same applies to working hours, noise and the periods when a route is blocked. Those constraints do not change what can be built, but they change how long it takes and in what order.
Asking the question in the right order
The useful sequence is to establish the access first and let it filter the methods, rather than choosing a method and then testing whether it can be delivered. That reverses the usual order of the conversation and saves the most expensive kind of rework, which is the kind that happens after something has been manufactured.
A record of the access route, taken as photographs and measurements before anything is designed, is the cheapest instrument available for this and the one most often skipped.
Establishing the access before the method
- 1Record the full route from the public road to the working position, with photographs.
- 2Note every restriction on the route: width, height, turns, gradients and surfaces.
- 3Establish whether a vehicle can turn on site or must reverse the whole way.
- 4Establish whether anything can be laid down on site, and where.
- 5Establish where a lifting machine could stand and what ground is beneath that position.
- 6Ask whether every position a piece has to reach can be reached from there.
- 7Ask what the erection sequence requires of the site, and whether the design assumes it.
- 8Ask what happens if a delivery arrives out of sequence.
- 9Establish where scaffolding can stand and whether it conflicts with the delivery route.
- 10Establish where waste leaves and where materials wait.
- 11Establish whether any part of the route involves a neighbour, a shared access or a right of way.
- 12Start any process involving a neighbour early, because it has its own timetable.
- 13Use the access record to filter the construction methods before one is chosen.
Common mistakes to avoid
- Choosing a method of construction and then testing whether it can be delivered.
- Reading delivery order as logistics, when the published entries treat it as a design constraint.
- Assuming a piece that fits the design also fits the route to its position.
- Planning a lifting position without checking what every lift has to reach from it.
- Forgetting that scaffolding, storage, waste and parking compete with the delivery route.
- Leaving a shared access or right of way to be arranged once the programme is fixed.
- Underestimating how far an inaccurate first course or first row propagates upward.
When to involve a professional
- What a given access route and site can accept is established by survey and by the contractor and lifting professionals, not assumed from a plan.
- No dimension, weight, vehicle size or lifting capacity is stated here, and none can be inferred from any description given.
- Lifting operations and temporary works associated with them are designed by qualified professionals for the specific site and sequence.
- Shared access, rights of way and neighbouring structures carry obligations in many jurisdictions that sit outside the scope of this guide.
- Where a method of construction is being considered, the supplier's own delivery and erection requirements apply alongside the designer's.
Frequently asked questions
Questions readers ask about this topic
Can site access really rule out a construction method?
Yes. Manufactured construction trades site work for larger pieces that arrive complete and cannot be trimmed, so if a piece cannot reach its position the method is unavailable regardless of its other merits. That is why the published entries describe access and craneage as design constraints.
Why does delivery order matter so much?
Because on a constrained site there is nowhere for a piece to wait. A unit arriving out of sequence occupies the space the next one needs, and where nothing can be laid down, an inconvenience elsewhere becomes a stoppage here.
Does this apply to work inside an existing building?
It applies most sharply there. The mezzanine entry describes access for members, the room needed to lift them and the sequence in which the space can be released as shaping the arrangement before any preference about materials does, which is the same constraint at a smaller scale.
When should the access be surveyed?
Before a method of construction is chosen, so it can filter the options rather than invalidate one. A photographic and dimensional record of the route from the public road to the working position is inexpensive and is the instrument most often missing from an early conversation.
What if the only route runs past a neighbour?
Then a separate process with its own timetable is involved, and it is worth starting early. Arrangements of that kind cannot be compressed at the end of a programme, and discovering the need for them after a start date has been fixed is a common source of delay.
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