Has a project of yours been held up by late culverts? Or have you been promised a lead time you weren't sure was realistic? The honest answer to "what's your lead time?" is that it depends. A small order of standard units can leave the yard as soon as a truck is available. A large custom package can take months from award to first delivery. The difference comes down to a handful of factors, and most of them can be influenced.
This guide covers what drives precast lead times, how they add up on different types of project, and practical ways to shorten them. It is written around RCBC box culverts, but the same logic applies to headwalls, bases, pits, cable trench and other custom precast.
Everything else, from award to delivery, sits around these three. The stages below show where the time goes.
Procurement approvals and contract negotiations on larger projects often take longer than planned, which leaves suppliers working to award dates that aren't realistic. Understand your own procurement and approval process and how long it really takes. Ask your supplier whether they can review the contract early, in parallel with evaluation, and whether any work can start before formal award. Most importantly, make sure the lead time you have been given is based on a realistic award date.
Small, standard-specification culverts may be available from stock, so lead time is limited only by transport, unloading resources and laydown space on site. Large and custom culverts are made to order and go through the stages below.
Large and custom elements, including rail structures, need structural design of the precast components. This ranges from simple changes to an existing design through to full layout drawings for complex structures with many precast components. Design typically takes 1 to 4 weeks. Ask your supplier what design is needed and whether any of it can start before award. Our post on precast design processes explains who does what at each step.
Large or critical structures often need an independent design check under the project specification. This is done by the client or arranged by the supplier. Check the specification early and confirm your supplier has allowed time for it.
Review and approval of drawings and quality documents varies widely with project complexity and the number of stakeholders involved, and it is often the longest single wait in a precast program. Talk to your principal early about how the review process works and how long it takes. If the project has several structures or stages, ask your supplier to stage design and approvals so the highest-priority structures go first.
Once designs are approved, production is scheduled, starting with the moulds. This can be a one-day change on a standard mould or up to four weeks to build a custom project-specific mould. Raw materials are scheduled in parallel. Ask about any long-lead materials. Also confirm the delivery dates of any items your project is free-issuing for casting in, such as rail fastenings, conduits or fixings. Production can't start until they arrive.
Casting time is set mainly by the number of moulds. As a rule, one mould produces one element per working day. For example, 20 units on two moulds take about 10 working days to cast, and 150 units on three moulds take about 50 working days. Adding moulds shortens the program but adds cost, and moulds commissioned in stages create a ramp-up period. Ask your supplier how many moulds they plan to use and how many units they can cast per day.
Precast elements must reach a set strength before they are transported, usually 80% of the specified strength. For example, a 50 MPa mix must reach 40 MPa. Without acceleration, curing can take 14 to 28 days; accelerated methods such as steam can bring this down to as little as 7 days. Ask how your elements will be cured and how much time is allowed from casting to delivery. Each unit cures individually, so early castings are ready for delivery while later units are still being made. This suits staged installation on larger projects.
Once elements are ready, truck availability and load-out slots at the yard affect delivery. So do factors on your side: laydown space, truck access, unloading equipment, crane size and weather. Element weight affects both transport and craneage; see understanding the weight of precast concrete. On complex projects, plan deliveries early with your supplier and make sure they have a dedicated logistics contact. Our post on complex deliveries covers this in more detail.
Production can occasionally be held up by weather, defective materials or resource constraints. Ask your supplier what contingencies they have in place and how they will tell you about any problems.
The table shows how the stages combine on three common types of project. These are illustrations, not quotes. Your project's timeline will depend on its own scale, design and approval requirements.
| Stage | Standard units from stock | Modified standard units (e.g. 20 units, custom lengths) |
Large custom package (e.g. 150 units, new moulds) |
|---|---|---|---|
| Design and approval | None | 1–2 weeks design, plus client review | 3–4 weeks design, plus proof check and client review |
| Moulds | None | Changeover of a day or two | Up to 4 weeks to build |
| Casting | Already cast | About 2 weeks on two moulds | About 10 weeks on three moulds |
| Curing to first delivery | Already cured | 7–28 days | 7–28 days; first units delivered while casting continues |
| What usually sets the date | Transport and site readiness | Drawing approval turnaround | Award date, approvals and mould build |
Is faster always better? Not necessarily. If your install date has some flexibility, tell us. A production program that fits around other work in the yard can sometimes cost less than one that has to be squeezed in. What matters most is that the program is realistic and agreed in writing.
Planning around the holidays? Our plant is closed from 21 December 2026 to 1 January 2027, with deliveries resuming from mid-January.
Use this checklist with your supplier on your next project.
Send us what you have, even if the design isn't final, and we'll give you a realistic date for your job. Where the timeframes are clear enough to plan around, our quotes include a draft production program, and our Critical Path approach keeps it on track.