Monarflex Roofing underlay
What is a roofing underlay?
A roofing underlay is placed under the exterior roof and its primary function is to work as a shield that pro-tects the thermal insulation material and the building structure from the effects of the weather. The roofing underlay thus works as a secondary roof.
Secondly, the roofing underlay must function as the primary weather shield during the construction period. The construction period should naturally be kept as short as possible as the roofing underlay are con-structed to work as the secondary roof, not the primary.
How does a roofing underlay function?
The roofing underlay acts as a condensation barrier, which leads condensed water away from the under-lay, and thereby also the insulation material.
Roofing underlays can be divided into two groups dependening on the construction of the roof where it is used:
• Ventilated roofs – roof construction which needs ventilation gap above and below the roofing un-derlay. The insulation material must never touch the roofing underlay.
• Diffusion open roofs – roof constructions where only ventilation above the membrane is needed. The insulation material can be applied just under the membrane.
Before starting to install a roofing underlay it is extremely important to consider the slopping angle of the roof, as there are some minimum demands. These demands are often dictated by national traditions or requirements. However a general rule is that the roof slop must never come beneath 12,5° slopping angle when using a plastic based roofing underlay. Please consult local rules for minimum overlap and slopping angle for either vertical or horizontal installation.
Importance of accessories
In order to get the optimal protection out of the roofing underlay it is extremely important to recognize that the accessories used for the installation is just as important as the membrane itself. By using the Monarflex accessories a total system is formed, which will assist the roofing underlay in being the best possible protection for the total roof construction. Further information can be found under accessories.
Choose the right product
When looking at the tremendous selections available on the market for roofing underlay it is quite over-whelming to get an overview. However choosing the right product for the construction is of up-most importance if the product is to last the lifetime of the exterior roof, which for the most common roofs is approximately 25 years.
The following conditions most be evaluated before choosing the product:
• What kind of exterior roof is used and can UV (sun light) shine in on the roofing underlay or not
• The construction type must be considered, is it a ventilated or non-ventilated construction
• Is it a boarded or non boarded (only rafters) roof construction
• Angle of roof slope
• Duration of the construction period where the roofing underlay will be exposed to conditions of the weather e.g. sun light, rain, snow, wind etc. - long term or short term
• Climate conditions should be considered – condensation build-up
• Position of the building, e.g. sea site or in land site
When looking at which product to use for different projects, it is difficult to give a answer, as it is very im-portant to get the right product for the right construction. Please consult our data sheets for further information.
At Monarflex "we are setting the standard"