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IsoBoard Installation:
Over Purlin Insulation
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Over Purlin Insulation.
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IsoBoard Over Purlin Insulation
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In South Africa, the bulk of retail and industrial buildings are steel-sheet clad frames, where 70% of the heat gain is through the roof.
IsoBoard over purlin insulation is the most cost effective method of achieving thermal efficiency in these builings.
Industrial developments to improve staff comfort and productivity.
Agricultural applications such as poultry-, pig-, mushroom-, crocodile- and fish-farming requiring consistent optimum
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growth conditions, and temperature controlled environments such as vegetable, flower and fruit processing areas and wine cellars.
Warehouses containing perishable and temperature sensitive goods.
Retail developments to provide comfort and reduce air conditioning costs.
"ISOBoard® high density 32-36kg/m3 rigid extruded polystyrene 100% closed cell insulation board of .... mm thickness and 600mm wide (with polyethylene treated kraft slip sheet factory applied to upper surface), with tongue and groove joints, fixed concurrent with roof covering, over steel purlins at approximately .... mm centres, with 5mm gap between boards butt-joined over purlins."
Handle and install with care to prevent damage to board edges. Store boards flat within original packaging until required.
Boards are to be protected from adverse weather conditions and direct sunlight for the storage period.
In potentially dusty conditions during construction or after, boards are to be wiped clean with a weak softened water solution immediately prior to over purlin installation, to remove possible static charges present on the board surface. Please contact IsoBoard for any queries with respect to the above.
IsoBoard is readily cut to length on site using a sharp blade or hack-saw.
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Application Guide
Wipe boards clean with a softened water solution immediately prior to installation. This removes any static charges built-up during the transport and handling of the board, preventing dust particles from adhering to the board. Boards are laid from apex to eave, always beginning and ending on a purlin. Where necessary, boards are to be butt-joined centrally over purlins, with a 5mm expansion gap between boards. Note: Butt-joined boards may not align.
Longitudinal jointing is effected using the tongue and groove edge profile,enabling the boards to be locked together tightly.
Fix roofsheet concurrently with IsoBoard so that IsoBoard is secured positively between purlins and roofsheets, using roof screws.
A factory applied polyethylene laminated kraft slip-sheet is required to separate IsoBoard from S-ribbed Chromadek or similar painted roof-sheets, to prevent possible noise caused by different rates of expansion.
See table below for recommended purlin spacing limitations for unsupported IsoBoard allowing for a 15mm deflection at mid-span.
Note that the recommended purlin spacings are reduced under Chromadek due to the higher temperatures experienced, and for the higher aesthetic requirement in domestic applications.
IsoBoard can be supported using aluminium T -sections, should purlin spacings exceed the recommended maximum.
Profiled roofing closers or cover strips should be used, if damage by birds etc. to exposed board ends can be expected.
In Industrial and Commercial applications where the designed purlin spacing exceeds that recommended for IsoBoard, please consult your nearest IsoBoard Regional Distribution Centre for installation advice.
The full text of the Large Scale Fire Test as conducted by the CSIR Building Technology unit with respect to the over purlin installation method, report no. BF 510/020-5600-5664, is available on the IsoBoard website, click here.
| IsoBoard Thickness |
Maximum Purlin Spacing |
Domestick and Chromadek |
| 25mm |
1100mm |
900mm |
| 30mm |
1400mm |
1200mm |
| 40mm and thicker |
1600mm |
1500mm |
Please refer to Application Guide 1.7 for the IsoBoard over truss insulation alternative.
Stock lengths of 8m, 6m, 4.8m in 25mm, 30mm, 40mm & 50mm thicknesses are generally available through your nearest Regional Distribution Centre. Contact us for a quotation.
Boards can be ordered to a specific length up to 8000mm where the order volume exceeds 50 cubic metres, to obviate off-cuts.
Lead times: five days ex-stock; twenty days ex-manufacturing.
Order IsoBoard with slip-sheet for use under Chromadek or similar painted roof sheet.
Order IsoBoard with square edge profile if board is to be supported by T or H-sections.
Please click on the thumbnails below to see the detail on the schematics.
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