Decking supports, posts and feet

What do decking supports do?

They hold the frame off the ground, carry its load into firm soil or a slab, and let air and water move underneath. Four kinds are in everyday use: concrete pads, posts, ground screws and adjustable pedestals (also sold as decking feet, deck supports or adjustable decking feet).

Which kind of support should you choose?

What do pedestals cost and how tall are they?

London Stone’s adjustable pedestals, with VAT as shown, cost:

A 20 mm self-levelling slope corrector at £3.60 corrects slopes up to 5 percent, and a rubber pad at £3.60 protects roof membranes. London Stone gives no load figure or material for these.

Millboard’s DuoLift is height-adjustable from 15 mm and self-levelling from 35 mm, up to a combined 350 mm. It has a joist cradle for joists 15 to 60 mm, a 20 mm self-levelling joint, a 45 mm riser and a 45 mm foot with a 220 mm base. NBS lists it as 30 percent glass-filled nylon 6 with 100 percent recycled content, fitting joists up to 69 mm wide. No page gives a load rating. Ecoscape’s composite pedestals are 100 percent recycled polypropylene and work with steel, aluminium, plastic or wood joists; its guide doesn’t cover roofs or balconies.

How many supports do you need?

It depends on the joists and the supports’ rating, so there’s no single answer. Cladco’s one post per m² is its own guidance for its concrete posts. For pedestals, take the spacing from the pedestal and joist maker. Our frame estimator counts members from spacings you enter, and the joists guide has the board makers’ joist centres.

What goes underneath?

A firm base and a weed membrane. One UK builder lays geotextile under the deck so weeds don’t push through the gaps six weeks later. DuoLift needs a solid, stable substrate and shouldn’t sit directly on soil. See laying decking on soil, grass or concrete for each surface.

Is there a height limit?

Not in the product pages, but the rules apply. In England, decking more than 30 cm above the ground normally needs planning permission, and guarding is expected above a 600 mm drop. Composite Prime recommends a professional installer above 600 mm. See planning permission and balustrades.

What about balustrade posts?

Those are separate parts, fixed into the frame structure and sized by the balustrade maker. The balustrades guide covers the height and opening rules.