The question: ‘Which system is better to use, concealed fix or screw fix?’ has concerned the industry for quite some time, particularly in the light of claims that screw fixing is more cost effective and “does the same job” as a concealed fix roof. This comparative analysis serves to remove this confusion by investigating the benefits of concealed fix over screw fix profiles.
Over tightening of screws is one of the most common installation flaws. Even when the most skilled roofers are involved, with an average of 36,000 screws per 6,000m2, the probability that over tightening will occur is extremely high. This installation flaw causes denting and washer damage, both of which lead to corrosion.
Dents are caused when screws are over tightened thus deforming the rib of the deck. Despite the drainage capabilities of the best of roofs, dents allow water to pond and remain around the screw. Corrosion will eventually occur as the screw has exposed the base metal to the “ponding” water.
Also refer to Long Length Roofing Solutions for more information regarding long length roofing solutions.
Figure DD CA 001 - Corrosion Caused by Ponding of Water
Meanwhile, damage to the neoprene washer can occur in a similar fashion to denting, as the over tightening action of the screw squeezes the washer to one side, breaking the watertight seal between the screw and the hole.
Figure DD CA 002 - Neoprene Washer Damage Caused by Over Tightening
Concealed fix decks have greater rib heights than screw fix decks. This increases their strength and water drainage capacity. Higher ribs enable water to drain from the roof at a faster rate. Some Australian manufacturers recommend the use of screw fix decks down to a 2° pitch, whereas the world standard is a minimum of 5°. Any deflection in the steel work could reduce the effective pitch to 1° or less, allowing water to pond.
Concealed fix decks are more robust and as such give better resistance to foot traffic and damage by trade and maintenance personnel. Some screw fix decks, due to the nature of their profile, cannot withstand the same force exerted on a single pan or rib and are thus highly susceptible to foot traffic damage.
The availability of the Fielders® Mobile Roofing Mill for concealed fix decks enables long lengths to be rolled on site, thus eliminating the need for costly step joints and the inevitable consequences of their eventual failure (see “Long Length Roofing Solutions”). This is further backed with Fielders® unique 20 Year Watertight Installation Guarantee (terms & conditions apply).
Concealed fix profiles are suited to a diverse range of applications. Fielders® range of concealed fix decks provide many options for different requirements, whether these be budgetary, durability or environmental issues. KingKlip® is a premium grade, robust deck with a unique “Over and Under” clipping system. HiKlip® is designed specifically for extreme cyclonic conditions and has the greatest water drainage capacity of the three profiles.
The final benefit of our concealed-fixed roofing over screw-fixed roofing is the Fielders® 20 Year Watertight Installation Guarantee (terms and conditions apply). Fielders® is confident in the strength and longevity of our concealed-fixed roof cladding and is able to offer eligible customers this unique guarantee.
HiKlip® 630
KingKlip 700®
Freeform™
Figure DD CA CFR 005
