Like their name suggests, top-fix brackets are for balcony connections which are installed after the floor substrate has been installed.
The main driver for this is often offsite manufacture, whether it be a timber frame construction or a pre cast plank system. Another key reason is fixing to existing slabs on old buildings. With the UK government having removed planning restrictions, conversion of office buildings to residential has become much more common, and therefore post fixed (or retro fixed) brackets are required. Existing buildings typically require more tolerance to be built into the design.
Because the balcony is bolted on to the building, imposing significant loads on the building frame, design and fixing details should be agreed at an early stage of the project. Thermal conductivity is another key consideration with post fixed brackets. Balcony connection points can cause a cold bridge from the cold balcony to the warm inside, so a thermal break must be specified to reduce the risk of heat loss and condensation forming at cold points inside the building.
Our patented Glide-On™ system, offers a lightweight alternative to steel-frame balconies. Using steel arms and an aluminium construction these cassette balconies enable faster, simpler and safer onsite installation along whilst still incorporating the benefits of offsite construction.
Whilst the Cassette® system and steel frame balconies are similar in terms of cost there are often other savings. For example, the lightweight cassettes require fewer connections to the building reducing the costs of the connection anchors and brackets etc.
Using post-fixed anchors on pre-cast slabs can bring a number of variations. The thickness of the slab can have a significant effect on the design.
When using a hollow plank, the voids (or hollows) around the anchor should be filled with a structural grout. This is best practise to ensure the bracket is fully supported underneath and around it. We understand that planks layout are often not easily changed. We do however recommend that consideration should be made for where joints are, as this can make a considerable difference to structural fixings and performance.
Timber frame construction is becoming more common place in schemes throughout the UK.
With cross laminated timber construction operating very different from concrete, the bracket design needs to be considerably different.
For the first timber frame project we installed, we learnt a lot about these differences through conducting a drawn out R&D program. This involved multiple tests and improving the performance of the bespoke connection to achieve an anchor which minimises the deflection on the balconies.