How to Use an Acrow Prop

HOW TO USE ACROW PROPS

An acrow prop (also called a masonry prop) can help support overhead loads in building and construction, preventing them from collapsing when working on them.

They come in a range of sizes from 0 to 4 and are telescopic. This ensures they’re versatile for the majority of needs in construction. They’re made to BS4074 safety standards.

They have a threaded inner tube, a welded top plate, and a threaded outer tube with a welded base plate, collar, handle, and pin. The thread allows you to change the height, and the pin prevents the inner tube from moving when fixed in place.

A strongboy will be the plate supporting the weight and attached to the acrow prop.

As they are load-bearing, it is vital to ensure you use the correct acrow prop and strongboy for the task. This means you must account for the weight they need to support, as well as bear in mind weight fluctuations (such as someone walking on the top floor or heavy tools).

Acrow props must be the correct height for their use. Don’t attempt to fill any gaps with timber offcuts or similar. Weight loads should also be even, not sparingly relying on just the support of one or two props.

Structural engineers and a competent trained person should be involved when installing acrow props and monitoring the continuous need and adjustments.

 

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Why are acrow props used?

The modern galvanized steel models replaced wooden props in the 1990s, ensuring a safer and more reliable system. Where wood would have to be cut to size and used only once, metal acrow props can be adjusted to size and reused for multiple jobs.

Acrow props can be used in scaffolding as additional support or support during renovation or building works.

This can be when:

• Creating a hole for a new doorway, window, or archway
• Replacing an existing opening
• Removing a wall and supporting the ceiling
• Bracing framework for stairs, walls, and columns
• Repairing beams, lintels, canopies, and ceilings
• Supporting trenches for groundwork

They allow any building or renovation work to settle, as well as allowing access to upper floors.

 

How to use an acrow prop

When using an acrow prop, you will need your props and strongboy wall props. The strongboy blade supports the masonry or brickwork and is then supported by a single acrow prop.

You may also need to use sole boards if your current flooring or ground is unlevel or not strong enough to take the weight of the prop.

Before installing your acrow prop to support overhead work, you need to ensure you have the correct preparation in place:

1. Measure the area you will be removing. This could be a whole wall or a hole for a door or window. The strong boy brackets will be placed in a gap of two bricks from the hole’s edge.
2. Draw a mortar line in the exact place where your strongboy will be installed. An engineer or architect can help guide on spacing and positioning.
3. Use a drill to remove the mortar from the joint. Any mortar left behind will affect the ability of the strongboy and prop to hold weight evenly.
4. Fix the strong boys to the top of the props. Ensure there’s no movement so they are fitted correctly.
5. Position the acrow prop in front of where it will be installed and adjust the height. Once correct, place your pins straight through the holes by the inner tube to keep the height.
6. Move the acrow props into place, inserting the strong boys into the gap in the mortar created earlier. Push into the gap as far as the strongboy handle allows (you may need to tap with a hammer or mallet). The top of the strongboy blade should be fully engaged with the brickwork or masonry.
7. Use a spirit level to ensure the strongboy and acrow props are straight and even.
8. Screw the collars closed until tight and even. You can use braces to connect the acrow props and offer additional support.

Once installed, acrow props must be checked regularly to ensure the weight is still held and the acrow prop is stable. As work progresses, they can become loose or need adjustment.

The load capacity may also change as you progress the work, with more capacity needed for heavier equipment and more workers.

Generally, new mortar or masonry requires around 24-48 hours to settle and harden, after which the acrow prop can be removed. But check with instructions and factor in how much new material there is. A prop should not be removed until the structure is entirely sound.

They’re only designed as a temporary solution, so they should not be used long-term.

 

Ensuring safety on site when using acrow props

Don’t forget your PPE, which you can purchase from Speedy when hiring power tools and equipment.

When using acrow props and carrying out the work required, always wear a hard hat, gloves, and eye protection. The work may require a dust mask and heavy work boots.

• Ensure the correct height and weight limit are being used for your task.
• Check props and strong boys are fully level using a spirit level. Even a slight deviation can affect their stability and safety.
• Check over the props and strong boys before use to ensure good condition. There should be no wear, rusting, or pins missing.
• Regularly check the props are still positioned correctly and at the weight capacity needed. If not, replace them. This should be done every few days.

 

FAQs

How many acrow props do I need?

The general advice is to have a pair of acrow props per 900mm (3 feet). This is the absolute limit, so don’t exceed this.

For particularly heavy overhead weights, increase this. Using horizontal braces can help make this even more supportive, especially if using more than two acrow props.

 

Which height acrow prop do I need?

Acrow props come in five different sizes, from 0 to 4. As per BS guidance sizes, they’re relatively standard no matter the brand and where hired from.

 

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Generally, the smaller the prop, the higher the safe weight load (SWL). Weight is measured in kilonewtons (KN) or kilograms (KG), and height is measured in millimetres (mm) or metres (m).

Acrow props are adjustable, with a working range. Their maximum weight capacity will be reduced when extended to their full size.

Below is a guide to the acrow props offered through Speedy Hire:

• Size 0: 1005mm up to 1830mm. Safe Working Load of 42 KN at 1050mm through 22 KN at 1830 mm.
• Size 1: 1750mm up to 3130mm. SWL of 34KN at 1600mm through to 12KN at 3120mm
• Size 2: 1980mm up to 3350mm. SWL of 39KN at 1900mm through to 11KN at 3400mm
• Size 3: 2590mm up to 3960mm. SWL of 35KN at 2170mm through to 7KN at 3975mm
• Size 4: 3200mm up to 4880mm. SWL of 20KN at 3100mm through to 7KN at 4900mm

If you hire acrow props from Speedy, we have a guide on the maximum height and weight of each of our models available and a range of accessories you may require for your specific job, such as additional boards and scaffolding.