Structural Stability During Masonry Alterations
In their own words, the role of the H.S.E is to provide advice, information and guidance, to raise safety awareness, to inspect, investigate and to take enforcement actions.
We find it unacceptable that the H.S.E do not provide any temporary masonry support guidance. Albeit the best recognised health and safety organisation in the world they are failing the individuals that carry out one of the most difficult & dangerous tasks within the construction industry.
We wish to share our knowledge by providing guidance and a code of conduct to raise safety awareness and to reduce the same needless recurring accidents.
MASONRY ALTERATION GUIDANCE & CODE OF CONDUCT
A. Plan and prepare prior to propping to prevent poor performance.
Look at all options, including the option of removing the masonry above a proposed opening, especially if in poor condition which will reduce the dangers connected to temporary masonry support and will also increase long term stability of the structure.
(Photo courtesy of Hogs Back Builders)
B. To know and to perform your legal responsibilities and duties of care to the workforce, the public & to your clients. It is the legal duty of the designated designer to identify all risks involved within a task; including the hidden & higher risks of eccentrically propping.
C. Ensure that all of the workforce involved understand the sequence of works and the correct procedures, ensuring nothing is lost in translation with foreign language speaking work colleagues or a work mate with communication difficulties.
D. Fully understand the capabilities of temporary masonry support equipment before using to ensure the equipment safely offers sufficient work/fitting access without overloading and is the most suitable for the task. As every project is different each task must be planned upon its own merit, do not recommend equipment on a whim or comment on a project until knowing all of the information required to discuss and to plan correctly within accordance of the specific task.
E. Never rush masonry alterations, gain the ability to price a project correctly which reduces haste during the task, over price if necessary but never under-price. Altering masonry or fitting steels is not a task to claw back revenue from other task losses.
F. Understand the importance of a load-point and to know the weights and loads of a structure that require temporary support. Fully understand how & why masonry collapses to prevent it from happening. Reduce the risk of collapse by gaining the knowledge of how to stabilise a structure.
G. Wear the correct protective clothing/equipment for head, hands and feet. Carry out tasks at height within the working at height regulations.
H. Do not weaken the integrity of a structure. Example; cutting exterior brickwork upon an existing property to continue a cavity to a new extension. Remedy; stop cavity cut outs below a proposed opening until the permanent support is in place. Ensure further structural stability by carrying out repairs and remedial works when necessary. Remove or redirect soil/waste pipes and fill in missing masonry/voids and existing cracks before any alterations take place.
I. Understand that all existing propping methods not only weaken a structure when fitting they also rely upon this weakened and unpredictable lateral strength to work correctly. Do not de-stabilise the integrity of a structure through vibration with large hammers, stitch drill beds & joints to remove brickwork and to fit tongues which also reduces carcinogenic dust particles and/or drill diamond core holes for needles to decrease instability which will also minimise internal wall damage upon finished rooms upon floors above.
J. Fully understand the dangerous relationship between the variable safe working load of different sized Acrow props and the further decreasing working load of the different distances from wall to prop when eccentrically propping with tongued attachments.
K. Do not use the last 100mm of the tongue of a prop attachment unless also bracing the structure, as the unpredictable working load is less than 200Kg and is not safe as the bendable tongues and different torques on Acrow props can distort & destabilise a structure.
L. Without any warning the traditional tongued prop attachment dangerously misuses an Acrow prop by changing the direction of the load onto the side of the Acrow props inner tube of which is designed only for vertical loads from head plate down to the foot plate. Reduce the higher risk of curving an inner tube by using the correct sized Acrow prop when eccentrically propping and extending the inner tube of an Acrow prop no more than half way from the outer tube.
M. Understand the different masonry alteration scenarios and know that a variety/combination of temporary support equipment is to be used that not only holds up masonry but also stabilises a structure, supports all of the masonry (to avoid injury from falling debris) and of which gives sufficient working/fitting access without dangerously overloading the structure above.
N. To have the ability to read and fully understand drawings and to know structural engineers and architects are legally permitted to make assumptions to reduce costs from further site visits. Be aware that it’s the builder’s duty to check all measurements on site and to ensure all generic assumptions within drawings and of temporary support designs are correct before permanent supports are fabricated and prior to any alterations taking place.
O. To have the ability to discuss and to question a structural engineer’s design and/or choice of temporary support equipment in a polite manner when recognised that not most suitable. Ensure the variable working loads of the equipment to be calculated is not just another dangerous assumption.
P. The stability & lateral strength of masonry is unpredictable & varies upon every structure and will depend on the length of the opening, the mortar mix (cement or lime), the age & the quality of the masonry workmanship. Do not rely solely on propping methods just because they worked on the last project as the next task could be totally different. Do not take short cuts, ensure future generations are shown the correct way and not taught the same bad habits as past generations due to generic assumptions and a lack of correct guidance.
Q. To have the ability to read and understand temporary masonry support equipment instructions before using, or to listen and to understand when verbally read out by someone.
R. To have the ability to carry out a task within the instructions without assuming correct use and to understand that when warnings are not in place due to Caveat emptor the correct level of caution must always made and further guidance should be sought after where in doubt, whether this is from a paid professional which specialises in temporary masonry support or through reading further up to date guidance.
S. Never leave eccentrically loaded props or braced masonry openings unattended or overnight as both methods are designed for access during a task and not a substitute for concentrically loaded Acrow props when unattended. Due to live, static and the further unknown dynamic loads leave a sufficient amount of masonry in place or wedge, prop, dry pack or build at sufficient points within the new opening during tea breaks and/or at the end of the working day when a permanent support is not in the final resting position.
T. An opening should not be removed down to the full depth to gain the correct fitting access for tongued prop attachments or even for access for mechanical lifting equipment as it increases the risk of greater collapse due to the masonry having a larger void to fall and also creates a higher risk of accidental knocks & removal of fully loaded props during demolition. Proven through risk assessments, the safest method is to remove only a sufficient amount of masonry to allow the fitting of the permanent support. Once the permanent support is in its final position, packed and cured, then the rest of the opening can be removed in a safer manner.
U. The traditional tongued prop attachment was designed in the mid 1980’s when the typical opening was smaller and a cavity size was only 50mm, however due to changes in construction design a cavity has at least now doubled to 100mm and over 150mm upon new properties for further thermal value and open plan living accommodation has vastly increased opening sizes within a typical residential rear extension.
Attempting tasks which require longer & wider steels with welded top/bottom plates for larger openings and bigger cavities and still only using out of date tongued attachments is where more problems of collapse through over extending even further from the wall to gain sufficient access arise.
V. Fully understand that masonry alterations are specialist tasks and to know all temporary support equipment is dangerous when used by less knowledgeable personnel.
W. A responsible builder is capable of questioning his own knowledge and able & willing to adapt to required change to keep up to date. Never stop learning as this information is not exhausted and will be up-dated from time to time due to further research & inevitable changes in construction design.
Construction Industry Research & Information Association
TONGUED PROP ATTACHMENTS