Roof Talk 101 The Best Educational Roof Blog In America: December 2015

Thursday, December 17, 2015

Roof Talk-101 3 Types of Moisture in Low-Slope Roofing Systems

Thomas J Taylor, PhD

Roofing systems must be designed and installed to address the many sources of moisture that can affect a building. Roofing manufacturers can provide the materials with a range of properties and options for the roofing system designer, but because each building is unique the final responsibility for ensuring that moisture and condensation don’t cause problems lies with the architect, system designer, project engineer, and/or roofing system professional.

Several years ago, SPRI issued an advisory bulletin on moisture and its effect on roofing systems. Their classification of the types of situations leading to moisture build-up is a good way to think about the main scenarios. I’ve listed them here, along with some general roofing system guidelines that may be useful. Of course, these guidelines should be superseded by those of a professional roof system designer.

1. Buildings with Small Amounts of Occupancy-Generated Moisture

These are the most common situations, covering office, retail, and warehouse spaces, for example. Warm air migrates upward and carries moisture with it. In northern climates, regardless of the membrane type, condensation can occur between the membrane and the insulation. Here is what to do in this situation.

Try to always use two layers of insulation with staggered joints. This helps prevent migration of warm, moist air up to the underside of the roof membrane. Warm air and moisture generally move upward, so drying out the roof system during warmer/sunnier days is a slow and difficult process. The goal should be to minimize or prevent condensation in the first place.
If a single layer of insulation is used, install cover boards, especially a high-density polyiso board, and use staggered joints.
If the membrane is to be fully adhered with a water-based adhesive, special care is needed to select the right one. Some have been shown to re-liquify in the presence of moisture.

2. Buildings with Large Amounts of Occupancy-Generated Moisture

This category includes paper mills, laundries, buildings with indoor swimming pools, and the like. The building’s air handling and ventilation systems should be carefully specified to take into account the moisture loading. Also, the entire building envelope needs to be designed and constructed in such a way that damaging condensation and moisture build-up doesn’t occur. It is critical that a building science professional experienced in these types of building occupancy and designs be involved.

Some approaches used by building design professionals for these buildings involve the use of air and vapor barriers. Care is needed to make sure these are applied properly and without any damage to their integrity. Pay particular attention to how they are terminated around the perimeters and at penetrations.
Remember that roof membranes are essentially impermeable. An air and vapor barrier placed lower in the roof system can prevent any water that has managed to leak in from going elsewhere.

3. Construction–Related Moisture

Most construction practices release some amount of moisture into the building space. These can be as straightforward as drywall installation and painting although these are typically relatively short term. However, some practices can release large amounts of water over a considerable time frame into the building. Concrete slab floors have been a challenge to use with some flooring materials, and building design professionals have methods to cope with the moisture release.

Concrete roof decks can present a challenge for roof system designers especially in new construction. Regardless of the type of concrete, significant amounts of water remain after curing is completed.

There is very little correlation between cure time and the amount of water remaining. Guidelines such as not closing up the system until a minimum of 30 days after pouring and forming are not particularly effective at reducing or eliminating issues.
Concrete in new construction that appears to be dry rarely is. Water takes a long time to diffuse out of a four inch-thick slab. In fact, the NRCA no longer considers the “plastic sheet test” to be a viable indicator of concrete’s surface dryness. That test involved taping a plastic sheet to the surface and monitoring moisture under it.
Many roof system designers require concrete decks be covered with a vapor barrier. As with buildings that have occupancy-generated moisture, care must be taken to ensure that these are specified and installed correctly. Roof membranes are essentially impermeable and any moisture that does get into the roof system will not have a path out.
Adopt a “belt and suspenders” approach to the roofing system and make sure any vapor barrier is terminated around the perimeter and penetrations properly. To do this, use two layers of insulation with staggered joints. When installing a fully adhered membrane with a water-based adhesive, make sure the adhesive will not re-liquify in the presence of moisture.
Make sure professionals who have experience with this type of construction are involved. These could include structural engineers, building science experts, and concrete suppliers.

The vast majority of roof systems give trouble-free performance for many years. When problems do occur within a few years of installation, it could be due to installation defects or moisture build-up. Roofing manufacturers try to provide a wide range of material choices so that the design professional can configure the optimum system for each building. The guidance offered here might help you to ask the right questions. However, to lower the risk of issues, make sure design professionals experienced with moisture and humidity in your region are involved.

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Thursday, December 10, 2015

Roof Talk-101 How to Help Homeowners Understand Ice Damming

Paulo Vieiradias

The cold winter season is the time when many homeowners see icicles hanging from their eaves and/or water coming in the house due to ice damming on the roof.

There are three main causes of ice damming:

Poor insulation from a house ceiling. An attic with inadequate or deteriorated insulation can cause ice damming.
Lack of ventilation. A house with proper ventilation allows the necessary cold air to mix and cool the hot air from the house, which slows the snow melting down.
Leaking gaps between the living space and the attic. These spaces allow extra heat to “escape” into the attic, which warms the space and melts even more snow.

Snow on the roof will eventually melt, but if the heat from the house causes the snow closer to the roof to turn into water, then that water can either go down slowly to the gutter or travel under the shingles. There is no heat at the gutter, so snow will remain there, creating a barrier. The water that is moving down will hit that cold snow barrier and then freeze again. This creates a dam (ice damming), which will hold the remaining water on the roof.

Shingle roofs are designed to shed water; they cannot handle having it freestanding. That is why a good quality leak barrier is needed at the eaves. To help your homeowner understand the importance, you can perform a simple test with a bottle of water. This will show that every nail going through the leak barrier is automatically sealed.

The most important thing a contractor can do to help homeowners with ice dam problems is to first clean the snow off the roof (following strict safety rules) and then create exits for the trapped water.

In the long term, the contractor should:

Seal the living space.
Install adequate attic insulation.
Make sure that the attic is properly ventilated.

Preventing ice dams and icicles may not be possible at all times, but these are measures that can be taken to help stop water from entering the house.

Thursday, December 3, 2015

Roof Talk-101 10 Tips to Help Homeowners Choose the Right Roofing Contractor

The biggest obstacle homeowners or business owners face when looking to fix or replace their roof is choosing the right person to do the job. After a damaging storm, they need to quickly get back to normal and get the necessary roofing repairs completed. But that doesn’t mean they should just choose the first contractor who knocks on their door. Finding a contractor who is trustworthy, honest, and professional may sound difficult – but that’s where you come in. Contractors should share these 10 important tips with homeowners to show them that your company is reputable and can be trusted to protect their home and their wallet.

Get local referrals. There is less chance of potential issues or scams when you choose a contractor from your community. They are more familiar with local rules and code regulations and have a relationship with area crews and suppliers.
Look for manufacturer designations. Manufacturer designations are considered a badge of honor because the contractor must pass certain minimum requirements to be factory-certified (although, some manufacturers have more stringent requirements than others).
Research Better Business Bureau (BBB) ratings. Some contractors blow in (no pun intended) right after a storm looking for work, so it’s important to look them up on the BBB website and make sure they have a good score. Stay away from contractors who do not exist on BBB.org.
Get an extensive warranty. Not all contractors can offer manufacturer warranties that include coverage of the contractor’s workmanship. If a contractor installs the roof incorrectly, it may take months or years for the damage to show up and insurance won’t pay for it. If the contractor won’t fix it (or worse, has gone out of business), your only recourse is to pay for their mistake yourself.
Be concerned about safety. A contractor without a training or safety program may not be the best person for your job.
Check for proper licensing and insurance. The contractor should have insurance for all employees and subcontractors and be able to provide a copy of their insurance certificate for validation. Not having adequate insurance could potentially lead to litigation between a contractor and homeowner if a roofing employee sustains an injury at the home. Most states require licensing for contractors, but that does not stop unlicensed contractors from attempting to do the roofing work. In states where licenses are required, make sure your contractor provides you with a copy of their license and confirm their status online.
Pay your deductible. Any contractor who claims that they can handle the repair without having the homeowner pay their insurance deductible is committing insurance fraud and endangering the homeowner. The insurance deductible is the responsibility of the insured, and the contractor should reflect that in the quote without inflating the estimate to cover all or part of the deductible.
Handle your own claim. A contractor who says they are “a claim specialist” or can “handle your insurance claim” may be breaking the law. In most states, it is illegal for contractors to act on behalf of the homeowner when negotiating an insurance claim. Any contractor who opens the door to potential legal action is not acting in your best interest.
Don’t give in to pressure. Watch out for a contractor who pressures you to sign a contract before the insurance company has estimated the damage. Some contractors say they can work with whatever your insurance company settles upon, but the homeowner needs to ensure it’s not just any amount, but the right amount. The contractor should thoroughly examine the home and check that their insurance adjuster didn’t miss any damages.
Know your material choices. A contractor who does not offer you different shingle options is not looking out for your best interest. The style and color of the shingles you install can affect the resale value of your home.