Formwork is temporary, but the result it produces is permanent — dimensional accuracy, cover to reinforcement and surface finish are all set before the pour and can't be corrected afterwards without cutting the concrete back out. A specification for formwork needs to define these things precisely, not describe the job as 'build shuttering and pour'.
Dimensional tolerance
The spec should state the required tolerance for line, level and plumb of the finished concrete face, referenced to the relevant standard (typically National Structural Concrete Specification tolerance classes for the element type). A retaining wall and an architectural feature pour have very different tolerance expectations, and the price should reflect which is being asked for.
Formwork panel joints, tie positions and the release agent used all affect the finished surface, and where an exposed or architectural finish is wanted, this should be named specifically since it changes the formwork system and the labour involved.
Rebar cover and fixing
Reinforcement cover — the distance between the outer face of the rebar and the concrete surface — must be specified and maintained with spacers appropriate to the exposure class of the element, following the relevant structural design (typically to Eurocode 2 / BS 8500 durability requirements). Undersized cover leads to reinforcement corrosion and cracking years after the pour, well outside any period a contractor can be easily held to.
The spec should also confirm bar diameter, spacing and lap lengths are being installed per the engineer's reinforcement drawing, not adjusted on site to suit whatever material is on hand.
Pour sequence and construction joints
For any element too large to pour in one continuous operation, the spec should define the pour sequence and the position and detailing of construction joints, including any waterstop or joint preparation required where the element needs to be watertight (basements, retaining walls below grade). An unplanned cold joint in the wrong place can create a weak plane or a leak path.
Curing and striking times
Curing method (covering, curing compound, or controlled moisture retention) and minimum curing duration should be stated, along with the minimum concrete strength or time before formwork can be struck, based on the concrete mix design and ambient conditions. Striking formwork too early risks damage to green concrete and long-term strength loss, and this is a step a rushed programme can be tempted to shorten.
What a thin formwork quote tends to leave out
Engineer-approved formwork design for anything load-bearing or unusual in shape, concrete testing (slump test, cube samples for strength verification), and an allowance for weather protection during curing in cold or wet conditions are commonly missing from a basic price.
- Reinforcement cover specified to exposure class, not assumed
- Defined pour sequence with construction joint detailing
- Concrete cube testing for strength verification
- Minimum curing duration before formwork strike
- Weather protection allowance for curing in cold conditions
Common questions
What happens if rebar cover is too thin?+
Reinforcement too close to the surface is more exposed to moisture and carbonation over time, which corrodes the steel, expands it, and cracks the surrounding concrete — a defect that typically appears years after the pour and is expensive to repair.
How long does concrete need to cure before formwork is struck?+
It depends on the mix design, ambient temperature and the load the element needs to carry once exposed — this should be calculated for the specific pour rather than following a fixed number of days regardless of conditions.
Do I need cube testing on a small domestic pour?+
For structural elements — foundations, retaining walls, load-bearing slabs — cube testing gives an objective verification of strength and is worth specifying, even on smaller domestic-scale pours.
Get a formwork specification with tolerance and cover defined
We specify tolerance, rebar cover and pour sequence against the engineer's design before any concrete is ordered.