Concealed- Fixing also known as a secret fix, is designed for very low-pitched roofs. Due to clips under the sheet holding it down, the sheet is not punctured with fasteners and therefore remains completely watertight even at a very low slope.
According to Metal Performing Technology, Concealed Fixing is a method where the roofing sheets are fixed to the purlins with a clip system. The roof sheeting hides the clips completely and provides a neat, watertight product. The roof sheets are not pierced with any nails or screws. No holes are made in the roof covering; this is to eliminate the risk of leaks.
These sheets not being punctured also accommodate expansion and contraction of the sheet without damaging the material. Ultimately, this method is also designed to provide a continuous length of roof covering without end-laps.
Concealed fixed roofs are then completed off with clean lines, and there are no visible fixings. Nevertheless, it is very important that this profile is produced on a machine using a good roll design to eliminate any possibility of the profile changing during the manufacturing process.
For those interested in concealed fixing need to understand that the profiles of concealed fix roofs are both aesthetic and functional. When designing a low-sloped roof, a defined rib and a wide, deep pan are needed to deliver excellent water run-off at slopes as low as 2 or 3 degrees. The height of the rib is important as it also provides structural strength, acting rather like a mini I-beam.
The design of the clips is also something that needs to be considered; because this is the “anchor” that will secure the sheet to the sub-structure and hold it down in case of high winds. The strength of the clip will be determined by the material that is used as well as the thickness of the clip, which in turn helps to determine the minimum wind-uplift resistance of the system.
In closing, you must consider the complete roofing system before specification as the roofing system design will define the manner in which the clip locks into the sheet profile. Installing concealed fix roofing is a process that needs experts, feel free to visit www.jcproofing.co.za for queries.