Choosing the right Modek GRP roof sheet

MODEK’s GRP products can be selected along a range of criteria, depending on the requirements of the application in question.

• Colour and clarity
• Profiles
• Weight
• Dimensional tolerance


Colour and Clarity

More than 70% of the heating effect of the sun is carried by light that falls between 350 and 800 nanometres – generally, the visible light spectrum. By changing the wavelengths of light that are transmitted through a material – in other words, by changing the colour of the material one can effectively alter the levels of solar gain to avoid overheating.

MODEK GRP comes in a range of standard colours: clear, white (opal 50), green and blue. Certain domestic products are also manufactured in grey, bronze and a colourful range of stripes.

In addition to coming in a range of colours, MODEK GRP sheeting can be either clear (which creates direct lighting) or slightly opaque (for diffuse light). The diffusion is achieved through the inclusion of randomly dispersed fibreglass reinforcement material in the sheet. Diffuse light is often desirable in applications where even lighting and controlled heating is required. Please see "Choosing the right material and colour" and "Using rooflighting for heating" for more information.

Profile

MODEK can manufacture GRP sheeting to match all profile shapes generally used for non-translucent roofing and cladding, to any transportable length.  

Weight

GRP sheeting is classified according to its mass rather than its nominal thickness, as thickness can vary from profile to profile even when the same product weight is used. All continuous-line laminating plants in the world manufacture to a mass parameter, not thickness, expressed as a nominal weight per surface area. In South Africa the metric unit used is kilograms per square metre of product (kg/m2).

MODEK manufactures GRP in the following standard weights:

• 1.1kg/m2
• 1.4kg/m2
• 1.8kg/m2
• 2.4kg/m2
• 3.0kg/m2
• 3.6kg/m2

Other weights can be manufactured to specification depending on particular requirements.

Please see "Choosing the right MODEK product" to see which mass is best suited to a given application, or contact MODEK’S Technical Department for advice.

Dimensional Tolerances

The following extract from SABS 1150/1984 describes the dimensional tolerances applicable to MODEK GRP sheets.

• General The nominal dimensions of a sheet shall be as specified by the purchaser.  
• Length The actual length of a sheet shall be at least equal to the nominal length, and shall not exceed it by more than 20mm.  
• Width The actual width of a sheet shall be at least equal to the nominal width, and shall not exceed it by more than 15mm.  
• Rectangularity Any deviation from squareness shall not exceed 10 mm.  
• Edge trueness Any departure of any edge of the sheet from a straight line shall not exceed 15 mm.