The case FOR Mechanical Fixing — what is it?
1. First it is FOR the supporting and restraining of panels of Stone or like that are individually attached to a facade on a substructure or substrate.
2. They have to be secured in place so as there is no down load onto the panel below, that is the bottom of the panel carries the load and the top fixing is placed in the position so that there is clearance between the bottom of this bracket and the top of the restrained panel (no down load ). Load charts for required brackets are available from suppliers.
3. Mechanical Fixing is best described as being a dry fixed BRACKET, secured by either a bolt to steel work, screw bolt or Through bolt to concrete or masonry substrate, or Pan headed S S wood screw onto plywood or compressed sheeting and then there is no reliance on the epoxy or glue that is used with the chemically injected methods that have been widely used in earlier times. There is no good in making the panels compleatly ridgid with all the fixings ( 2 on top and 2 below ) epoxied together into the panel — if you do use a hard based epoxy to effect the joint width on the underside of the panel, YOU MUST USE A SOFT silicone filler in the top fixing point, so there is movement in the joint, as all Cladding and materials do buckle and bend and this method then allows movement and support. You must remember that there is always need for joint width correction because of many factors, among them the panel sizes vary.
4. Why Mechanical Fixing is needed, is to allow alignment of the stone panels in particular designs, or it may be to make room for services behind the facade. The further out the cavity widens and the bigger the stone panels become the heavier and stronger the Mechanical Fixing has to be manufactured and engineer certified. Then when this is determined, there has to be allowance then for the wind loadings as well as the dead load as the walls or facades go up in height.
5. When installing panels it is generally and nearly always done with set size Mechanical Fixing brackets used for Tooled or Worked face Stone Panels AND adjustable brackets where the stone panels are sawn or polished face products, as no substrates are EVER straight and PLUMB.
6. Whenever possible when working with deep cavities, it is best to try and use substructures ( 41 mm x 41 mm Universal channel) as it will reduce the size of the fixing brackets by 1 size normally AND it then allows you to secure the main substructure into the substrate where it is best placed instead of where it falls in the height of the facade.
7. When working with small cavities ( 5- 10 mm), it is best advice to use Mechanical Fixing when the product comes in at over 36 - 40 kgs/ m2 — which is all product over 18 mm thick and weights in excess of 5 kilo’s / piece. The main problem is that the epoxy or glue Might or Will secure the panels but it is normally stronger than the product it IS SUPPORTING and then one surface has to let go — what happens next is usually very expensive