Granite – Technical Specification
Formed millions of years ago, granite is one of the hardest substances on earth, rating 7 on Mohs hardness scale.
Granite joints are finished with a small ariss to the top edge. Silicone sealant is applied to prevent water ingression.
Tolerance in granite is ±2mm
Due to thermal expansion granite can expand up to 1mm per metre. A gap of at least 3mm should be left at each end of the worktop when fitted and filled with decorators caulk. When granite is joined to other materials (such as glass, steel or wood) an elastic type of adhesive, for example polyurethane, is required for expansion.
Overhangs and supports
Any overhang extending more than 300mm must be supported.
Hob and Sink cutouts
Granite sink / hob cut outs are barred front & back (fitting of steel support bars to give additional support to cutouts), Without steel supports bars, the length of a cut out is reduced considerably. Large cut outs need to be scored and cored on occasions. This leaves the corners of the cutout in place, ready for removal on-site by the installer. Granite is susceptible to ‘blowing out’.
This occurs when contact is made with the material whilst cutting or grinding. This is very common in large particled granite. ie. we fill and seal the affected areas with epoxy resin (colour may vary) to ensure the material is not left with any sharp edges or ‘chips’.
Slips (kit form) around sink and hob cutouts are fitted in certain circumstances, if tops are too long and depending upon type and size of cutout etc.
- A minimum of 120mm is required between two hob cutout.
- A minimum of 100mm is required between hob and sink cutouts.
- A minimum of 70mm is required between two sink cutouts.
- Sink cutouts are placed a minimum 50mm from the worktop front edge.
Internal profile edges on all edge detail other than bevel edge must have a radius of at least 60mm. Bevel edges don’t have this constraint as they are hand finished.
Upstands should ideally be 100mm high, as material less than this height is extremely fragile. Upstands are not normally cut from the same slab as the worksurfaces, therefore an exact colour match is not possible. Granite upstands are straight and rigid, gaps will be visible where there are variations in the wall profile. Plastering or tiling should ideally be completed after the worksurface installation.
Granite is highly scratch resistant but not scratch proof. Small scratches of less than 25mm in length are considered ‘within tolerance’ and are considered acceptable.
Although Granite is one of the least absorbent stone’s, it can still be stained by grease, wine, coffee, nicotine, fruit juices and other strongly coloured substances. Granite worksurfaces are sealed upon installation and must be resealed every 6 months. Any spillages must be removed immediately as delay could result in permanent damage.
Stainless Steel Sinks
Please specify the preferred undermounting of Stainless Steel Sinks. Silicone sealant may be rendered ineffective when plumbing the sink in, it is important that the sink is re-sealed by the plumber, or the 12 months guarantee will be invalid if the work is not carried out. If a waste disposal unit is fitted to an undermounted sink after installation, additional support will be required, otherwise your warranty may be invalidated.
For installations you will need to supply additional labour on orders, which have worktops weighing above 150kg. Every additional 75kg requires an extra person to assist with lifting. Size of ‘scant’ or ‘slab’, is a major factor in selecting the maximum usable length of a work surface. Approximately 2.8m x 1.3m is the largest work surface we are able to manufacture, this may be drastically reduced if you require a cutout, especially in granite with larger crystals. Due to the weight of granite, please ensure that your units are level and securely fixed.