What is ‘spec busting’?
Although the term ‘value engineering’ can refer to the practice of finding innovative ways to solve a design problem more cost-effectively, in some cases it does mean simply substituting specified products for a cheaper alternative, in a similar way to ‘spec busting’.
Product substitution varies depending on the sector, the type of contract that the work is procured under, and to what extent the supplier has been involved in the specification process.
Some construction contracts disallow the substitution of materials without permission. Some include an “equal or approved” clause – often seen in local authority specifications.
However, ‘spec busting’ is still a concern throughout the construction industry and is a particular issue in the roofing sector at the moment.
Why does spec busting occur?
With budgets having been tight since the financial crisis of 2008 and subsequent austerity, there is pressure on contractors to drive down costs. Manufacturers are less able to hold large volumes of products in stock, meaning that product lead times are sometimes a challenge.
For example, if a type of roof tile is only available on a long lead time, or is considered too expensive, then the contractor may choose to replace it with a similar product. In some cases this cannot be avoided but it is important to recognise that substituted products can create problems.
The problems with ‘spec busting’ in roofing
Although it may be cheaper in the short term to replace a specified product, this can have a significant impact and lead to unforeseen costs in the longer term. For example, substituted products are not always truly “equivalent” and significant differences in quality, guarantees, weather resistance and environmental performance can compromise a design.
In a 2017 report, in cases where specifiers had problems with projects, 57% said that it was down to materials being substituted (*2017 NBS Specification Report). In these situations, roof tiles and systems may not suitable for the location or type of roof.
Substituted roof tiles may not be compatible with the rest of the specified roof system – our products have been designed and tested to work together to guarantee performance, but this is not always the case with a combination of materials from different manufacturers.
Product guarantees sometimes require roof systems to be specified using products from a single manufacturer. If one element is replaced, such as the roof tile or the underlay, then the roof as a whole won’t benefit from the guarantee, which with Marley systems is 15 years.
British Standards for the quality of roofing installation and environmental performance are becoming increasingly strict. To meet these requirements, products are becoming more highly engineered and are supplied with lengthy guarantees when they are specified as part of full roof systems, so ‘busting’ a specification can create significant risks.
Environmental credentials can be compromised by spec busting. If a product is substituted with another A+ rated tile for instance, the replacement may not have responsible sourcing certification. This can have an impact if the client is looking to achieve a particular BREEAM or Home Quality Mark rating.
Marley products have both BES 6001 responsible sourcing accreditation and an A+ rating in the BRE Green Guide, which provides additional BREEAM points, and switching to a seemingly equivalent product could impact a building’s sustainability credentials.
Can BS 5534 protect roof specifications?
The revisions to BS 5534, the British Standard for roofing and tiling, together with the proposed new dry fix standard, means that roofing design has become more complex. Manufacturers now work with designers and specifiers at the early stages of a project to ensure an entire roof system will fully comply with British Standards.
The quality and durability of some dry fix systems that comply with BS 5534 can also be a concern. Significant variation has been seen in the quality of components in dry fix systems – in some cases even leading to product failure. Swapping a specified brand of dry fix product may have an impact on the performance of the roof. The proposed introduction of a new British Standard for dry fix systems may help to combat this problem.
How to substitute building products successfullyThere will always be a need for contractors to substitute products in some cases. The processes that should be followed depend on the type of contract, but must be carried out with full awareness of the differences between switched products.
A roofing contractor should first make sure that any new products are suitable for the design, shape and pitch of the roof and will perform as the architect or project surveyor intended. They also need to check that the revised roof system meets BS 5534 as well BS 8612 – the upcoming British Standard for dry fix. In addition, they should obtain a bespoke fixing specification from the manufacturer, and ensure that all system components suit both the roof and the conditions found in the location of the property or site.
It is always best to find out if the client or specifier chose a product for a particular reason – such as performance, environmental criteria or guarantee. Lastly, in tenders and quotes, make it clear that costings are being provided for an alternative product.
If you have any further questions about roofing specifications or pitched roof systems, contact your local Marley specialist or use our extensive array of tools and resources available to help you on your next project.