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The Right Material For Your Re-Roof

Updated: Mar 15

A roof is much more than an aesthetically appealing covering for your commercial building; it’s the first barrier from weather conditions such as rain, hail, snow, extreme heat and wind. Because roofs are exposed to at least one of these elements on a daily basis, degradation and deterioration will happen over time.

As a roof deteriorates due to age and exposure, decisions need to be made about how to address the issue. For commercial roofs, retrofits will generally be for the flat roof portion of the structure(s), although metal and shingle roofs can be overlaid as well. Modification generally includes repairs generally along with some type of coating application to protect the surface of the existing system from further deterioration and seal it to prevent leaking.

When determining the right material to use for your project, a number of factors can affect your decision, such as the type of roof you have, funds available and your climate.

Pitched Roofs:

Pitched roofs are those that are visible as you approach a building. Aesthetic appeal is important, since appearance adds to the appeal and value of a building. However, durability of the roofing material is essential to get the most value for your investment.

The type of roofing material installed can add to the value of the property, or if poorly done, can detract from the building. The most likely scenario for a damaged pitched roof is a replacement roof system if it’s shingle or wood shake, or a replacement of underlayment if it’s tile, metal, or slate.

If replacement is needed, the property manager should consider whether to replace like-for-like or install an alternate roof system. Additional factors to consider include whether the structure is designed to hold the weight of the alternate roof system or whether an alternate system can effectively work with the existing shape or pitch of the roof structure. Tile, for example, may weigh ten pounds per square foot, or metal may need special considerations for low pitches.

Underlayments for pitched roofs affect durability. A #15 felt is the typical underlayment for a shingle roof and #30 felt for tile and metal. However, synthetic or modified underlayments which tend to have a longer service life may also be installed. It‘s a question of balancing the initial investment with the anticipated duration of service life.

The specific roofing materials that are right for your building will depend on the specific factors affecting your facility – but there are a lot of choices! If metal were to be an option, it could range from cold-rolled steel or zincalume to painted steel, painted aluminum, or even copper or zinc. Tile is available in various price ranges, in a selection of profiles and colors, ranging from hand-made sun-dried “sandcast” tile to clay and concrete.

Flat Roofs:

Generally defined as a roof that has a slope of less than 10%, flat roofs are typically less costly to install than pitched roof systems and can provide years of trouble-free service. A wide selection of options is available in flat roof systems.

The more typical systems installed on flat roofs are membranes, including TPO (thermoplastic polyolefin), PVC (polyvinyl chloride), EPDM (ethylene propylene diene monomer (M-class) rubber), APP (atactic polypropylene) modified bitumen, SBS (styrene-butadiene-styrene) modified, built-up systems and spray polyurethane foam.

The key consideration with a flat roof system is finding ways to extend its useful life. Routine maintenance is always recommended, as it will extend the initial service life. However, age and the elements will eventually necessitate consideration of alternative options. Fortunately, flat roof systems can typically be primed and coated to extend their useful life, avoiding the need for tear-off and associated disposal costs.

Depending on the type of flat roof system, acrylic elastomeric coatings, silicone or an emulsion may be applied over the existing roof to seal and protect it from continuing deterioration. Since flat roofs are generally less visible, appearance is not the critical issue as with a pitched roof, with durability and value becoming the primary drivers.

Climate Matters:

With any commercial roof, climate is a factor in the decision-making process. Some types of roofing materials provide better service in wet climates, others in dry and hot climates. Some materials degrade under ice and snow, while others shrink with heat and sun.

For example, in a climate such as Arizona, heat and the sun damage organic roofing materials faster than elsewhere. Some synthetic products tend to become brittle and/or shrink. Arizona technicians have been on roofs with installed membranes, which have shrunk so the surface is like a drum – step on it, it goes down, lift your foot and it pops back up. Fully adhered products may open at the seams, because the adhesive can become pliable with heat and lose its adhesive properties. Additionally, darker roll products may bring additional heat into the roof structure.

Another issue to consider is thermal-shock. This is what happens when a roof that is baking in the sun, which can be as hot as 180 degrees F., is rained on. The rain rapidly draws heat out of the roofing material, causing it to shrink as it cools. This rapid cooling can cause the roofing material to crack because it is shrinking on the surface faster than the bottom can accommodate. With rain, the roof temperature may drop as much as 100 degrees F. within a matter of minutes, which places a severe strain on the roof system. Products such as spray foam (inert once applied) and roll products such as TPO tend to accommodate rapid temperature changes more readily than other products.

Because your climate has a great impact on your roof, it can be helpful to obtain advice from a roofing service provider in the decision-making process when considering how to maximize useful service life of the roofing system while minimizing investment.

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