Contractors know that when they involve us during the early stages of the tendering process, we’ll have a set of tie details which will completely eliminate temporary shuttering and soffit shuttering, and all hot works (site welding). This saves them time and money and provides them with more visually aesthetic finishes, which is particularly important when the inherent thermal mass properties of concrete are utilised by way of an exposed concrete soffit.
Here’s an insight into how we eliminate temporary works and hot works, which results in savings on cost, programme and reduced risk to Health & Safety.
Predominantly along the tie beams – when they’re located within the floor zone, we introduce non-structural steel plates and or steel angles which are stitch-welded to the tie beams. These then act as temporary, and subsequently, permanent shuttering.
Also, on exposed soffit projects, the steel shutter is far more aesthetically pleasing because it hides the site poured insitu concrete and the cut edge of the hollowcore flooring unit.
The difference between that and the visible precast concrete which is poured in a factory environment is that it hides the two finishes and provides the end-user with a more visually attractive appearance. On exposed soffit flooring projects this is a particularly pertinent requirement. The reason why the soffits are left exposed is to optimise the inherent thermal mass that exists in precast concrete, and other types of concrete – which can subsequently reduce lifetime energy costs in buildings when it comes to heating and cooling.
As far as we’re aware, we’re the only company that is proactively pushing and promoting these amendments at tender stage, to offer the end user a better finish. The same applies to mitigating health and safety related issues regarding temporary works and hot works.
These methods have been adopted on historical schemes. However in our opinion, the steel industry could do more to raise awareness and actively promote best practice on how to integrate precast concrete flooring into steel frame buildings – and, how to do it effectively. Eliminating temporary works and hot works requires early involvement, often when we are approached at enquiry stage the design is already at an advanced stage, so it is often too late to accommodate our proposals. Beresford’s has worked on hundreds of schemes and our early design input has eliminated the need for temporary soffit formwork.
Hot works is essentially site welding of reinforcement to ensure a tie is achieved between the in-situ tie within the hollowcore floor and the supporting steel beam. There are endless risks associated with site welding – and protective measures that need to be put in place are very expensive. The work also needs to be carried out by a coded site welder which are hard to come by and expensive – and completed in dry conditions. A hot works permit needs to be in place prior to the work starting.
The steel beams would also need to be prepared for welding (paint removed) and then reinstating, which isn’t a simple process when you consider the beam may have already been treated with fire protection (intumescent paint). Site welding is also not appropriate when the steel frame is galvanised. All of our standard details mitigate all requirement for site welding.
To meet regulations, we recommend that where possible temporary works should be mitigated. The other thing associated with this type of temporary works is propping, which can sometimes be done from the beam – often though, it has to be done from the floor below which does create obstructions to follow on trades. So, if you remove any requirement for props being present you actually create a cleaner and safer environment for these trades and other site operatives to work within the footprint of the floor below.
The package is often misunderstood – and over designed. If quoting is done incorrectly, it can be eye wateringly expensive – it can also be coupled with other details that can be mitigated, for example, hot works, temporary shuttering and soffit shuttering. But also, there’s the commercial timing of it where we’re approached at a point where the steel frame contractor could already have been appointed and the design too far advanced for the changes to be adopted. Unfortunately, this is an industry wide problem.
This may be a controversial opinion – but once someone has been appointed and under contract, to incorporate our suggestions would require a variations to their contract. With most subcontract packages there are what we call pre-contract costs and post contract costs. Pre-contract costs are always more economical than post-contract costs.
Post-contract costs – or variations, which is where some contractors may seek to recover low margin project costs to recover more profit and more overhead recovery. So, if these details are incorporated pre-award, you are getting far better value for money than you would if it was post-award.
Raising awareness about how precast concrete flooring can be integrated more efficiently into steel frame buildings. It’s a skillset we want to retain within our industry, especially for students who are coming into construction.
Take Bison Concrete Products Ltd. At one time, they were the biggest hollowcore flooring manufacturer. They sponsored a Steel Construction Institute (SCI) Guide 351, which did outline some good practice, but we’re going back about 15-years. In our opinion, a lot of that guidance has been superseded by a lot of details we have in our standard portfolio. For example, the 351 Guide still recommends site welding of certain progressive collapse tie details, but we have a set of details that eliminate all site welding. With a lot of sites now, you have to put safety measures in place to prevent any weld spark – so you have to put up spark resistant sheeting which is very costly. Beresford’s can mitigate temporary works and hot works on site.
This may be a divisive view, but a lot of engineers come out with quite sound knowledge about the design of steel frame buildings and metal deck flooring – being a steel system, but also the design software packages are far more advanced with how to design metal deck flooring composite with steel frame buildings. In our experience of some of these software packages, they aren’t being integrated correctly to accommodate composite flooring design within steel frame buildings. But also being able to understand some of the nuances with precast concrete flooring being constructed with steel frame building.
The cost savings in some respects are immeasurable because if you’ve got a completed building with visible lines of insitu concrete that hasn’t been correctly shuttered adjacent to precast concrete soffits, then you’ve actually got a non-compliant project in relation to the architects specification. It may state a Type B finish, which is a BS8110 clause, and not a Euro code clause – so that type of finish would be in breach of that.
Also, if these details were bottomed out pre award on a steel frame package, you’ve actually got steel frame contractors competing on a level playing field because all of the details are refined and clarified, but you’ve also mitigated all the other issues of hot works and temporary works. Not only that, but you can’t put a price on safety – so you’ve actually made the building safer to construct and it becomes a more efficient approach to tendering.
We’ve developed our library of tie details with the experience of the people we employ. Various people within the team have actually worked for precast concrete manufacturers and steel frame contractors from a design and build perspective, and also our heritage has been installing precast concrete flooring for many years. Our operatives are feeding back in terms of some of the details and the problems associated with installing the flooring on steel frame buildings, but also accommodating the insitu concrete works associated with a bigger floor.