2016 PROPPING GUIDE
2016 PROPPING GUIDE
All temporary support must be planned, the equipment used is to be suitable and maintained to withstand foreseeable loads and should never be overloaded.
All practical steps must be taken to ensure that any new or existing structure does not collapse or become unstable through carrying out construction work.
The main cause of collapse during masonry alterations is overloading equipment due to under estimating loads, over tightening Acrow props and over extending the equipment from the wall to gain further access.
The safe working load of a prop attachment varies and depends on the size of the Acrow prop used, which pin-hole height is used, how plumb and how far the Acrow prop is fitted from the centre of the wall.
Fitting a traditional prop attachment reduces the safe working load of an Acrow prop by at least 90% due to the web of the attachment sending the load onto the side of the Acrow props inner tube, the Acrow prop curves and loses height when overloaded, over extended or when over tightened and is the duty of the user not to overload and work with an Acrow prop fitted with an attachment in a professional and safe manner.
Acrow props are designed to concentrically load on the axis only, (from head plate down to foot plate) and have a maximum safe working load of approximately 3,400 kg reducing down to 700 kg when the inner tube of the Acrow prop is fully extended?
Every opening without a load-point intact must be calculated on its own merit as loads will be different, the user must know what masonry requires support and the weight of the load to calculate the number of correctly used props and attachments required, maximum safe working load 340Kg when used within the up-dated instructions.
The traditional prop attachment was designed in the 1980's when openings were smaller and cavities only 50mm. Attempting tasks which require wider steels for wider cavities and still only using prop attachments is where further problems of overloading by over extending from the wall arise.
Prior to using a prop attachment you should identify that it is a suitable method to carry out the intended works and that it can offer the correct fitting space without dangerously overloading through over extending from the wall especially when using on the same side as the fitting/working area.
The traditional prop attachment can be used on single or double skin walls where each leaf is up to 4 ½” (112mm) thick, if double skin the maximum cavity is 2” (50mm). Ensure the blade is fully supporting the second skin.
The distance between props should be calculated from the assessment of the loading. Props will need to be fitted closer within larger openings with no load-point intact and shouldn't exceed 900mm even within smaller openings without using the Brick Brace to support the masonry in-between props, please see our masonry weight chart for guidance.
If the width of the intended opening is greater than 4 metres props should be horizontally laced and diagonal braced together using scaffolding poles and proprietary couplings or the Brick Brace safety system should be used over the opening to allow a prop to be moved safely during a task, reducing the risk of accidental collapse.
An overloaded prop attachment relies solely on the lateral strength within masonry which is always different especially within older lime and weak mortars and upon 9″ walls and cavity walls on larger openings with no load-point intact.
Pre-stress masonry with the Brick Brace before alterations takes place and support 100% of the masonry above the opening. Gain further fitting space, reduce repair time and achieve a guaranteed superior and safer finish.
Misusing the bendable tongue of a prop attachment severely reduces the safe working load of the Acrow prop. The tongue of the traditional prop attachment is too long to support only one skin of a cavity wall for the maximum safe working load to apply as it was designed to support single 4″ walls, 9″ walls and two skins of a 50mm cavity wall only. One linear metre of 4" masonry on a typical 2.4m storey height can weigh over 700Kg over wider openings with no load-point intact.
The Brick Brace safety tool and safety system are designed to reinforce the lateral strength of masonry, safely supporting all of the masonry above, reducing repair time for a guaranteed superior and safer finish. The Brick Brace safety tool was fully tested in multiples at C.E.R.A.M testing laboratories, (Stoke-On-Trent) and addresses all the issues of the main causes of minor and major collapse during masonry alterations.
DUE TO A VARIETY OF FACTORS, EVERY TASK OF SUPPORTING MASONRY IS DIFFERENT, PLAN AND PREPARE BEFORE A TASK AND USE A VARIETY OF TEMPORARY SUPPORT EQUIPMENT MOST SUITABLE FOR THE TASK AHEAD.
1, What is the nature of the task, is it remedial works, is it forming a new opening or enlarging an existing opening, what opening size is required, is the opening in the outer or inner skin of a wall or both?
2, what is the masonry material, what design (cavity or solid), what is the size of the cavity? What thickness is the wall, what bond is the brickwork and what mortar mix, cement or lime?
3, What are the existing ceiling heights, what is the direction of floor/joists, are they load bearing onto the wall or are they non load bearing?
4, On which storey height is the opening, is the height 2100mm typical lintel window/door height, is a steel fitted underneath load bearing joist/floor, is the existing joists fitted within the web of the steel or is the steel fitted in line with the non load bearing joists or floor?
5, Loads and weights; is a load-point intact, which masonry requires support and what is the total weight of the load that requires support.
6, Is ground support available, how much fitting Space is required, what equipment or variety of equipment offers the correct support and gives the safest fitting/working space without overloading equipment by over extending Acrow props further from the wall.
MAXIMUM SAFE WORKING LOADS
An Acrow Prop used from head plate down to foot plate, max S.W.L 3400Kg
An Acrow prop used within the props and needles method, max S.W.L 1700Kg
An Acrow prop fitted with a prop attachment when used within the up-dated guidelines, max S.W.L 340Kg
Acrow props come in 5 different sizes (size 0 to size 4), always use the correct sized Acrow for the task ahead. To reduce the risk of the inner tube of the Acrow prop from curving when propping eccentrically, extend the correct sized Acrow prop to the fourth pin-hole max.
Props exhibiting any of the following defects should not be used, a tube with a bend, a tube with more than superficial corrosion. A prop with a bent head or base plate, an incorrect or a damaged pin or a pin not properly attached to the prop by the correct chain or wire. Install props vertical to ensure that it can support its specified load. Props must never be used more than 1.5 degrees out of vertical. No more than 50mm out of true vertical for every 1.8m in height, this will decrease the S.W.L of the prop. Always wear gloves and the appropriate safety equipment, allow only the essential work force in the work area with no access to the public or to clients. Ensure that props are installed by a team that has the necessary knowledge to carry out the task. Ensure the base of your prop is bearing directly onto the surface and that the floor surfaces are capable of supporting the weight that will be placed upon them.
Further concentrically loaded Acrow props should be used to support joists and beams separately when working on load bearing walls due to the different possible live and static loads, always check the condition of joists and beams before propping, where in an unsatisfactory condition replace or repair before continuing. Reduce live loads further by ensuring the rooms above are vacated and closed to clients until works are complete.
Construction, Design and Management 2015
(Now in force on every British site including small projects)
Temporary Works (in Brief)
Adapt to individual requirements, especially regarding the design of the workplace, the choice of work equipment and the choice of working and production methods with a view in particular to reduce the effect of risk on health and safety. Adapt to technical progress, replace the dangerous by the non-dangerous or the less dangerous.
All practical steps must be taken to prevent danger and to ensure that any new or existing structure does not collapse or become unstable due to the carrying out of construction work.
The builder (contractor) must ensure they have the necessary skills and knowledge and capable of avoiding risks, to evaluate risks which can’t be avoided and be able to combat risks at source.
Temporary support must be designed, installed and maintained to withstand foreseeable loads and a structure must never be loaded as to render it unsafe to any person.
Work within health and safety guidelines; respect your legal responsibilities and respect the welfare of others around you.