Dave Osborne, technical manager for Swish Building Products explains why taking that extra five minutes to ensure an accurate site survey is more important than ever.
Accuracy is crucial in keeping project costs down and downtime to a minimum; two key factors in achieving a successful completion. With a number of the national housebuilders increasing the number of homes under construction to accommodate the surge in consumer demand and help alleviate the housing shortage, expectation and targets can start to take over and details can be missed.
Insightful site surveys
It’s difficult to say what’s the most influential factor in the smooth running of a building site but the inaccurate provision of materials can be particularly damaging, impacting the supply chain and the entire programme of works, from specification to completion.
Product specification, quantities, delivery and a hassle-free installation are all dependent on the quality and accuracy of the site survey. As with many things in life, the standard of a survey can be wide and varied, ranging from those requiring a crystal ball to an all-singing, all-dancing, top-notch one.
Known as either a schedule or bill of materials, this is in fact a comprehensive list of all the components needed to make the installation work.
If details are missing in the first instance, this can mean that components are missing from the bill of materials, inevitably leaving the site team short on parts. The knock-on effect of this is the added cost of extra materials, an increase in wages to cover additional time, and the over-all costs associated with an over-run.
This is particularly relevant to roofline products. If a building needs re-roofing for example, the fascia and soffits would need to be fitted before the roof cover materials. If the site were to run short on materials this would not only cause delays but could also leave the building exposed to unpredictable UK weather.
Some manufacturers have the capability to produce the bill of material in-house, offering peace of mind and reassurance. Added to this, they may then supply to site through an approved stockist, and carry out the installation through an approved contractor, both of which offer further assurance.
When creating a bill of materials specific to a project the schedule is restricted by the quality and scale of the drawings. The technical team has to work with the information provided; in an ideal world this should include roof plans, elevation details and section drawings. The section drawings are of the greatest value as they show, on a larger scale, details such as the eaves overhang. This kind of detail means that the technician responsible can be accurate in their specification of materials, sizes and quantities.
The best drawings are on a scale of 1:50 – most commonly used for section drawings. This ratio means that details are legible. 1:100 is considered to be the most widely used scale for plans and elevations. However, working to this scale on a new build – where there is no building to check against – can leave a considerable margin for error.
To alleviate this, best practise would be for site contractors and builders to carry out a mid-build measurement using similar, existing building stock as a yard stick. Once the production phase is underway, a measurement of either early-completion properties, phase one or show homes can be taken and used as benchmarks for the remainder of the build or the next phase.
For fear of stating the obvious, if a building exists a physical measure can be carried out – arguably giving the most accurate measurement. Visiting the site does not only ensure precision but surveyors can also spot hidden details, those which may not necessarily be shown on the drawings – such as recessed overhangs or elaborate design features. Larger blocks, particularly older properties, often have hidden valleys which require additional fascias and guttering. If these were unaccounted for and the fitter was unaware, carrying on with his installation, he would inevitably run out of materials before the roofline was completed.
The devil’s in the detail
Features that enhance the aesthetics of a scheme can be the downfall of an accurate survey. When making design and architectural improvements, such as a small eaves detailing or a feature extension, be mindful of the impact on the scheduling of materials. A simple change on paper can cause havoc further down the build.
In creating an accurate bill of materials the supply chain, contractors, and both the site and project management can avoid costly downtime, material wastage or shortage, prolonged hire costs, and the stress of a delayed programme of works; all of which work to support a sustainable housebuilding programme for the UK.