How far apart should Acrow props be spaced?

Acrow prop spacing depends on the load being supported. For load-bearing walls with timber floors above, space props at no more than 600mm centres. For concrete floors or multiple storeys, reduce to 450mm or even 300mm. Non-load-bearing walls can use wider spacing of up to 900mm. Always follow the structural engineer's specification — they will calculate the exact loads and required prop spacing for your specific situation.

What size Acrow prop do I need?

Acrow props come in sizes 0-4. Size 0 covers 1040-1829mm (low rooms, basements), Size 1 covers 1753-3124mm (standard rooms), Size 2 covers 1981-3352mm, Size 3 covers 2591-3962mm (high ceilings), and Size 4 covers 3200-4877mm (commercial). For standard UK ceiling heights of 2.4m, Size 1 props are typically used. The prop should never be extended more than two-thirds of its adjustment range, as this reduces its safe working load.

What is a Strongboy and when do I need one?

A Strongboy is an L-shaped attachment that fits on top of an Acrow prop and slides into a mortar joint in brickwork or blockwork. It supports the masonry above while the wall below is removed (for example, when installing a new opening or lintel). Strongboys are only suitable for single-storey masonry support and should not be used where the wall supports more than one floor. For heavier loads, needle beams are used instead.

Do I need a structural engineer for wall removal?

Yes, you should always consult a structural engineer before removing any wall, even if you believe it is non-load-bearing. The engineer will assess the loads, specify the correct steel beam or lintel, and provide a temporary works design including prop spacing and sequencing. Building Regulations approval is required for any structural alteration. The engineer will typically provide a specification drawing that your builder follows during the work.

What are sole plates and why are they important?

Sole plates are timber boards (typically 225x50mm or similar) placed under the foot of each Acrow prop to spread the load over a larger area of floor. Without a sole plate, the concentrated point load from the prop can damage or punch through a timber floor, or crack floor tiles. The sole plate should span across at least two floor joists (for timber floors) and extend at least 150mm beyond the prop base on each side.

Acrow Prop Spacing Calculator — How Many Acrow Props Do I Need?

Calculate the number, spacing and size of Acrow props needed for temporary structural support when removing walls or installing steel beams.

Opening Width

Width of the opening being formed

Ceiling Height

Floor-to-ceiling height where props are installed

Wall Type

Load-bearing walls require closer spacing

Floor Above

Concrete floors = closer spacing

Floors Supported

Number of floors above the opening

Support Method

Strongboys for light loads; needles for heavy/multi-storey

How We Calculate This

This calculator determines the number of Acrow props, their spacing, and the correct prop size based on the opening width, wall type, floor type, and number of floors being supported. It also calculates needles, strongboys, and sole plates needed.

Spacing guidelines

Load-bearing, timber floor: 600mm maximum centres
Load-bearing, concrete floor: 450mm maximum centres
Non-load-bearing: 900mm maximum centres
Multiple floors supported: Reduce to 450mm or 300mm centres

Prop sizing

Size 0: 1040-1829mm — Safe load 34 kN
Size 1: 1753-3124mm — Safe load 25 kN
Size 2: 1981-3352mm — Safe load 20.5 kN
Size 3: 2591-3962mm — Safe load 17 kN
Size 4: 3200-4877mm — Safe load 12 kN

Important notes

This calculator provides general guidance only. Temporary works design must be carried out or verified by a competent person (structural engineer or temporary works coordinator) in accordance with BS 5975 (Code of practice for temporary works procedures and the permissible stress design of falsework). Every structural alteration is unique and must be assessed individually.

Standards

Acrow prop use should comply with BS 5975 (Code of practice for temporary works) and BS EN 1065 (Adjustable telescopic steel props). The structural alteration itself requires Building Regulations approval and a structural engineer's design to comply with Approved Document A (Structure).

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Acrow Prop Spacing Calculator — How Many Acrow Props Do I Need?

How We Calculate This

Spacing guidelines

Prop sizing

Important notes

Standards

Frequently Asked Questions

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