Yesterday we discussed climate considerations for selecting the right roofing products, but there are also considerations from the building owner's perspective that must be considered.
First, the building owner's intentions for the building should be your top consideration in roof selection. If the owner intends to flip the building as soon as possible, roof system cost becomes the primary driver. However, long-term holders and owner-occupied buildings are best served with a roof system designed with long-term use in mind.
Second, insurance can affect the choice of a roof system. If the building is insured by a Factory Mutual (FM) company, the FM design and installation requirements must be followed to the letter. Other insurers may have their own standards to follow, so you should always check with the insurance company during the design phase to be certain.
Third is the budget. Long before the roof is to be installed you should have a roof inspection performed by a competent roofing contractor, consulting architect or engineer who will give you an unbiased opinion of when the roof will need to be replaced and the probable construction costs for the replacement. A consultant can tell you whether you can re-cover or if a tear-off is needed and can prepare construction documents that anticipate all of these considerations prior to bidding the work. Having an adequate budget for the roof can help ensure the building owner's needs are met.
Finally, you need contractors available who know how to properly install the desired roof. When selecting a roof, you should identify contractors available to install it. Using local roofers is a good idea as they can respond more quickly to problems than if they are located far from the job site.
Knowing what you need before you obtain bids and being sure you communicate these needs to the contractors can help make sure the roof you have installed will perform well and have a nice, long life.
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The amount and type of precipitation, temperature and wind are the aspects of climate that should most affect the design and selection of the roof system for a building.
A building located in a dry climate like the desert southwest does not need the same type of roof as a building subjected to daily rains like in the pacific northwest. Places that have high fees for wastewater removal may want to consider a vegetated roof to absorb stormwater. However, rain isn't the only consideration. Snow can drift and collect in corners, topping flashings and cause leaks. Hail can puncture the roof system, requiring a roof that can withstand abuse. If there is a wide temperature spread between winter and summer, a roof system that will expand and contract with thermal movement is a good choice.
Climate also affects the amount of insulation needed. Predominantly hot areas should consider a reflective roof system to save on cooling costs. In mostly cold climates, energy savings depend on the cost of heating energy compared with cooling, the slope of roof, insulation, and overall building dimensions. One resource to determine whether a roof will have energy benefits is the Department of Energy's Roof Savings Calculator. Heat sinks may also be considered for hot climates to lessen the amount of thermal shock that can occur when a roof is suddenly cooled during a rainstorm.
Identifying the wind uplift requirements is important in areas prone to hurricanes or other high wind events. Anywhere the wind gusts more than gale force should take wind into consideration (even a 40-mile-per-hour wind can cause a poorly attached roof to peel).
Tomorrow we will discuss considerations for selecting the right roofing products from the building owner's perspective.
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You know you need a new roof, but where do you start? The most common method is to call three roofers to get independant proposals and then compare. But how do you know what to get proposals for? How do you pick a roof system that is best suited to your building? A step-by-step look at the various factors that affect the roof (and the needs of the building) is the best approach to answering those questions.
Yesterday we discussed the importance of the building's characteristics in regards to selecting the right roof system. Today we will review evaluation of the existing roof and how that should play in to your decision.
Evaluate the Existing Roof
Existing deck construction and whether the roof drains properly or not will influence the kinds of roofs that can be installed. Decks with a slope greater than 2:12 can use most membrane systems, as well as roof systems like shingle or tile designed to combine watershed and
aesthetics. Slopes lower than 2:12 must be a water barrier system because they do not drain as quickly.
The type of deck may be the deciding factor in how the roof is fastened. Roofs over steel, lightweight insulating concrete, wood, gypsum and cementitious wood fiber planks generally are best installed with fasteners, while those on structural concrete are best adhered.
The condition of the deck is also important to consider. If the deck is in poor condition, re-covering the existing membrane is not a good option as the installation may ignore life safety issues. Ballasted installations, vegetated roofs or heavy re-covers may overload the structural capacity of the roof.
Drainage requirements should also be identified. If water stays on the roof more than 48 hours, the roof has a ponding problem. Because most manufacturers do not warrant areas of ponded water, the new roof should incorporate a way to remove the water, such as new drains or tapered insulation. The number and size of overflow drains should be identified. If the elevation of the roof gets higher due to a re-cover or from adding more insulation, it may partially or completely block overflows or bring the roof assembly to a non-code-complying height. This will mean that the overflows may have to be moved, added or changed, which is an expensive process. Increasing the thickness of the roof also may cause through-wall flashings and door thresholds to be too low.
It's important to identify anticipated abuse. If the roof has equipment that requires regular maintenance, there will be foot traffic on the roof. However, abuse to the roof can happen from window washing equipment and personnel, smokers and vandalism. If abuse is possible, the resulting design should incorporate extra toughness in the form of extra thickness or extra plies.
Tomorrow we will review a checklist of questions for you to ask the roofing contractors you request bids from.
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