Making an impact – the hope for a new British Standard on robustness
BS 5234 was introduced in 1992 with the intention of giving designers greater scope for specifying drywall systems and accounting for the conditions in which they will be used, but it is a much misunderstood Standard as Steve Halcrow explains.
When we talk to designers about strength and robustness of drywall partitions they invariably make the assumption that we are talking purely about impact resistance, an assumption made without realising and usually without knowing that there are other elements that should also be considered.
Before the inception of BS 5234 partitions were basically designed based on their overall stiffness, a function of the size and centres of the studs, the thickness and number of layers of board, and the height to which they were to be built. There was no formal consideration given to impact resistance and generally it was a case of just making the board thicker or using a double layer to make it more robust. In fairness there were fewer boards around then, and most of the “technical” boards which are now part of everyday drywall life did not exist, so the options were limited.
The arrival of BS 5234 meant that designers could now choose systems suitable for a range of uses. A partition constructed in a domestic dwelling will have very different usage requirements to one built in a school or public circulation area, and the Standard set out to make this clear and offer a method for selecting which option should be used in a given application.
It uses a method which consists of separating the basic ‘stiffness’ of a wall (the only real criterion for selecting a system in the ‘old’ way) from its resistance to dynamic impact from furniture, trolleys, human interaction, etc. By assessing and combining the capability of the wall to withstand these different conditions a designer could specify more accurately what they needed. The Standard also brings in other practical factors such as shelf loadings, door slams, sanitary ware fixings, etc, where required (though these are often overlooked).
In principle it is simple: first, make sure the partition is designed to accommodate the height to which it will be built, then check that the type and thickness of board is adequate for the ‘impact’ load it is forecast to experience in use. To comply with the Standard the system should satisfy these criteria and then the relevant additional ones such as those listed above.
What has happened in practice is that the Standard is widely misunderstood, probably attributable at least in part to its rather complex explanation of the recommendations it contains. Unfortunately the predictable result of confusion among designers is a tendency to revert to the ‘safe’ option, meaning the appearance of a plethora of specifications containing the words ‘Severe Duty’ at every turn.
In fact there are many instances where ‘Heavy’ or even ‘Medium’ duty under the Standard would be more than adequate for a given application, but we still see ‘Severe’ called up by the designer, for the reasons given. This is the go-to classification when one doesn’t understand the other options, but of course it results in over-specification on many an occasion and along with this comes unnecessary complexity of designs to manage and build, and of course additional cost.
Thankfully, prompted by a request from the GPDA, it appears likely that the Standard will soon be reviewed and the opportunity will be seized to remove the veil of mystery and confusion, with an improved BS being the ultimate result. Work should begin on this soon and we will keep you abreast of progress through these pages. We will also produce a members’ guide to the key points of the Standard, which will be available through the FPDC website.
