There may come a time when you want to undertake a structural alteration to your home, to perhaps make better use of your living space, or maybe to make a window larger for example. Before carrying out an alteration, you will need to ensure that any part of the structure you are taking away, does not require support. If it does, then using acrow props will be required.
Acrow props are strong steel tubular like instruments that consist of a 4 part system; A male section, female section, a winding collar and a small stout pin. The way acrow props essentially work is by the female section accepting the male, allowing the 2 sections to be fully adjustable to a suitable height. The sections have holes in them so that the stout pin can be inserted to keep them fixed at your chosen height. The props can then further be adjusted by turning the winding collar.
At each end of the male and female sections will be a steel plate which is usually about 150 mm x 150 mm. The plate is there to help the acrow props find a suitable bearing on both the ground and the force to be supported.
Putting The Acrow Props To Use
There are a number of ways to use acrow props but probably the most common methods are by using them in conjunction with either timber needles or strongboys. Needles in construction are short stout timber beams, and an acrow prop would be placed towards each end, where the load being supported is in the middle. Strongboys are a more modern method where only 1 prop is needed to fix to the strongboy, which in turn would then be placed in position to support the load.
Needles
If you need to support a wall and you have chosen to use needles, then the method would be to knock a couple of bricks through the wall large enough to put the needles through, and then at each end an acrow prop would be placed and tightened up until it is tight between the brick and ground level. This is a two man job and can be very trick to get the needles to balance whist setting them correctly in place.
Strongboys
Using strongboys is a far easier method as it is usually only a case of hacking out a mortar joint where the load is to be supported, and then inserting the long, thin arm of the strongboy in. As with the needles method, the acrow props are them tightened up securely. The benefits of using strongboys with the acrow props however, is that the load only needs to be supported by putting the props at one side of the wall.
You will also need to check the ground that you are placing the props on to ensure it is strong enough to take the additional loads you will be placing on it. If the ground is a timber suspended floor for example, then you would need to spread the load by placing stout board/s at right angles to the floor joists. This is assuming that the floor joists are sound themselves. Where the ground level is concrete and sound, the props can be placed directly onto the concrete, however, I feel it is always good practice to use a stout board to place them on.
Supporting any load bearing structure should only be undertaken by competent persons and should never be done without the advice and guidance of a structural engineer, professional builder and the local building officer.