Setting out and foundation tolerances
Where two worlds meet
Section titled “Where two worlds meet”Manufacturing tolerances are of the order of millimetres. Site tolerances — setting out, formwork, concreting — are an order of magnitude larger.
That difference is not a problem in itself. The problem arises when nobody measures where the two meet, in time.
What happens if it is not accurate
Section titled “What happens if it is not accurate”Accumulation
Section titled “Accumulation”Panels go up one after another. If a few millimetres are left at each, by the twentieth member it shows in centimetres — and there is nothing to be done there.
Forced fit in the structure
Section titled “Forced fit in the structure”A panel not bearing flat loads the fixings, and screwed connections were not made for that.
Window and door fit
Section titled “Window and door fit”Manufacture delivers the openings accurately. If the wall shifts, the window does not fit.
Time and money
Section titled “Time and money”Patching on site is precisely the advantage the technology was chosen for.
How to avoid it
Section titled “How to avoid it”Survey before erection
Section titled “Survey before erection”A topographic check: corner points, side lengths, diagonals, the flatness of the surface. Half a day’s work that saves days.
Levelling by design
Section titled “Levelling by design”Small deviation is manageable: a mortar bed or shims beneath the bottom track. That belongs in the drawings, not invented on site. Fixing the bottom track.
Recording the tolerance regime
Section titled “Recording the tolerance regime”In the construction contract: what deviation the structure will accept. That makes the responsibility clear.
The position of the hold-downs
Section titled “The position of the hold-downs”Where cast-in anchors are used, setting them out is critical — they cannot be moved afterwards.
Who should measure
Section titled “Who should measure”Preferably an independent party, or at least whoever is responsible for erection — not whoever poured the concrete. The aim is not fault-finding but finding out before erection whether levelling is needed.
The point
Section titled “The point”Accurate manufacture requires an accurate base. Half an afternoon of survey is the cheapest insurance for the whole erection phase.