Key points
- Precast concrete is mixed, poured and cured in a factory environment with ideal conditions and quality control throughout production.
- Elements arrive reinforced, finished and ready to install, without waiting for suitable weather or long on-site storage.
- Examples: hollow-core slabs, walls, boundary walls, stairs, columns and beams, and manholes.
- Plant certification (such as PCI) means a documented quality system and two unannounced audits a year.
The difference between ready-mixed concrete and precast concrete: the first is poured on your site into forms, while the second is cast in the factory as a complete element (slab, wall, step) and then transported and installed.
1) Advantages as presented by the National Precast Concrete Association
- Quality control: concrete is mixed, poured and cured in a factory environment, maintaining ideal conditions and quality control throughout production1.
- Fast installation: products arrive reinforced and finished, ready for installation1.
- No waiting for weather: no need for on-site storage, extra handling or waiting for favourable weather1 — important in summer heat, which makes on-site curing difficult.
- Durability: described as strong, durable and resilient against impact, weather, water, fire and corrosion1.
- Tested before delivery: performance testing and inspection ensure products meet specifications before reaching site1.
2) Where is it used?
| Element | Common use |
|---|---|
| Hollow-core slabs | Roofs and floors with longer spans and fewer columns. |
| Walls and facade panels | Warehouses, repetitive buildings, boundary walls. |
| Precast boundary walls | Plot, farm and project boundaries. |
| Stairs and landings | Fast installation without on-site formwork. |
| Manholes, tanks and septic tanks | Buried elements with factory quality. |
A general illustrative table; each element's design and connections are set by the structural engineer and the manufacturer.
3) Choosing a plant: certification
One example of plant certification is the Precast/Prestressed Concrete Institute (PCI) programme, under which each plant undergoes two unannounced audits a year, and which ensures the plant has a documented in-house quality system based on industry standards2.
- Ask for the plant's quality certification and product test reports.
- Ask for shop drawings of the elements and the details of connections to the structure.
- Check crane and truck access to the site and room to manoeuvre.
- Agree the warranty and how joints are sealed against leaks.
4) Pros and cons
Pros
- Factory quality and controlled curing.
- Fast installation and a cleaner site.
- Suits repetitive elements.
Cons and cautions
- Needs cranes and site access; transport has a cost.
- Connections between elements are critical structurally and for leaks.
- Changes after manufacture are hard and expensive.
To compare with other prefab systems see the comparison table.
Sources
The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.
- 1Choose Precast — advantages of precast concrete — National Precast Concrete Association (NPCA)
- 2PCI Plant Certification — Precast/Prestressed Concrete Institute (PCI)