Replacing Roof Offers Wider Choice Of Systems, Chance To Inspect Deck
If re-covering or coatings are not viable solutions, you will need to tear off the old roof and replace it with a new one. There are good things about this approach. It gives you a wider choice of roof systems that can be used. That's because you are less limited by the structural capacity of the deck or by compatibility with an existing material. The warranty periods available from the manufacturers are longer than with a re-cover. With a replacement, insulation can be upgraded to higher R-value materials. Finally, everything on the roof will be gone so you can inspect the deck for any repairs needed. A deteriorated deck will not hold fasteners in place so the likelihood of a blow off during high wind conditions can be mitigated if the deck is visible for repairs.
As noted above, code may require a tear off if there are two roofs already in place. And safety considerations may call for a tear off if there are doubts about the condition of the deck.
The biggest drawback of replacement is that the cost of removing the existing roof is greater than leaving it in place. You also add more trash to the environment. And drainage issues that were hidden by the existing roof may show up on the new roof. For instance, low spots on concrete decks that may have been hidden in the gravel of the old roof may show up on the new as small ponding areas.
Roofing Project Planning
Now that you have made the decision whether to re-coat, re-cover, or replace, there are more hard decisions. You need to decide on which system and which materials are best suited for your building. That means choosing what works best for your climate, the building construction, your insurance carrier's requirements, code restrictions, and your budget. Then you have to develop a project manual to be used for bidding the work to contractors. The project manual should include these specifications:
- Type of roof system to be installed. These can be by manufacturer or by generic type as long as all of the products are equivalent.
- Method of installation (adhered, mechanically attached, etc.).
- Amount and type of insulation and attachment method to deck.
- Whether or not the insulation should be tapered to provide additional slope to drain. (Always require tapered insulation at the drains.)
- Type of metal to be used for counterflashings, metal edges, copings, goosenecks, etc. and what type of finish you want on them.
- Building rules and regulations covering how the contractor can use the building, what security you require, working hours, facilities and utilities available for contractor use, elevator use, parking, staging and storage areas available, etc.
- Rules and forms for payment applications, changes to the work, etc.
- Bid form and a specimen copy of the contract that will be used.
Drawings are also essential for the project manual. They should include detail drawings of all penetrations and flashing conditions but, most important, unusual situations that are not included in the manufacturers' literature. Also important is a roof plan drawn to scale showing the location of all penetrations through the roof and other locations requiring flashings or other special handling.
Getting the Job Done Right
Once you have prepared all of the preliminary work, you need to bid the project and watch it under construction to be sure the contractor is providing what you have so painstakingly researched and documented. If you have done your best deciding on and specifying the most appropriate roof, picked a good, ethical, reliable, and experienced contractor, and made sure that the work was done according to the contract, you can also expect that the roof you put on will be the best choice for your building.
If you are not sure that you have the necessary expertise in roofing or time to do the research and document preparation, you can consider hiring an architect or engineer who has the knowledge and expertise to decide if you need a new roof and, if you do, determine the most practical way of proceeding. A competent consultant can also provide customized plans and specifications that define the scope of the work so that all bidders bid on the same work, and you don't have to be concerned about three contractors proposing three different systems with no way to compare them.
Karen Warseck, AIA, LEED AP, is president of Building Diagnostics Associates, a Hollywood, Fla., architecture firm. She is a contributing editor for Building Operating Management.