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XVII

Understanding the materials and their differences
Nail Strip and Cladding
The Nail Strip panel has a thin rib and wide tray with a perforated fixing
strip along one side. There is no need for fixing clips or the additional
operation of seaming. This ensures speed and ease of installing panels whilst
allowing for expansion and contraction. It can be used for vertical facade or
roofing applications. The plywood minimum thickness shall be 15mm. Nail
Strip panels are laid and fixed directly to the plywood substrate along the
perforated strip every 300mm with concealed screws or nails. The high rib is
then placed over the low rib and snapped into place along the length of the
panel.
Sealant Strip
Elastomeric sealants are used widely in conjunction with sheet metal
fabrications during roof construction. A wide variety of sealants is
commercially available, and each type has specific performance
characteristics. Sealant types currently utilized in roofing installations include
silicone, polyurethane, and butyl. Applications for sealants in roofing include
caulk troughs of surface mounted counter flashing/ termination bars,
penetration bonnets, coping stone joints, lap joints in sheet metal fabrications
(i.e. counter flashings, copings, etc.), fillers in pitch pans, and in​seam sealers
in metal panels. In order to achieve the desired performance of sealants,
there are several issues regarding the design and installation that require
proper attention.
Thickness of roof
If you own a home or commercial building, you’ve probably heard
about roof thickness. Whether your roof is sloped or flat, thickness matters
when it comes to choosing the right material for your roof. The choices are
more plentiful for sloped roofs. Low slope or flat roofs are another story. A low
slope roof is anything under 2 ½ inches of fall per foot.
When you think of flat roofs, the basic hot tar and gravel come to mind.
One layer of waterproof material, built up upon another, alternated with hot
tar, commonly referred to as Built-Up Roof (BUR). The final coat is hot tar
covered in gravel which keeps the UV rays of the sun and weather off the
paper beneath, protecting it from splitting or cracks. More recently, other
materials such as fiberglass membranes were developed. The benefits of a
tar and gravel roof are that it is usually the least expensive and is very fire
retardant.
Wind Resistance
It is very important to test the wind resistance of a roof. A typical home
with a rectangular floor plan has an equally typical gable roof. By simply
changing the roof into a hip roof—essentially doubling the number of
slopes—the home’s wind resistance is improved several times. Since wind
tends to uplift, reducing the overhang to 20 inches at most can further improve
wind resistance.
Flat roofs are another option that works especially well in contemporary
home designs. Traditional built-up roofing is much heavier and therefore

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