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B. FLASHING, DECK DRAINS & SCUPPERS
C. SLOPING
A. SUBSTRATE 1. Make sure that the substrate being used is what is called for in the plans. Plywood is always specified; OSB board, chip board, etc. is a substitution and should be documented very carefully. 5/8" is the minimum thickness with 3/4" being preferred. Make sure the plywood is exterior grade stamped. Most deck coating manufacturers do not recommend going over anything but concrete or plywood. Confirm that the joist size and type is what is being used. 2. The nailing schedule for plywood should be 6" O.C. in the field and 3" O.C. at the seams. This is an area that is frequently investigated in litigation and commonly overlooked in the field. Ring shank nails or screws should be used. This is usually spelled out in the deck coating literature. Green sinkers and box nails should not be used as they will loosen in the plywood over time. 3. Blocking is required at all plywood seams. This too is often overlooked and easy to document in litigation cases. The purpose of the blocking is to support the plywood seam and not allow movement that could crack the coating. Seams should be flat and smooth to insure that the final product will look good. 4. Concrete should be cured with water only. The finish should be a light broom finish. Curing time is between 14 and 28 days and will vary by manufacturer and coating type. If flashing is to be installed on top of the concrete it should be done within 3 days of the pour. Expansion joints should be designed into the deck and should be treated according to the manufacturer's details. B. FLASHING, DECK DRAINS AND SCUPPERS 1. Flashing details should be called out on the plans or specifications, but the minimum size should be 2" on the deck and 6" up the wall. Flashing should be galvanized or bonderized. Galvanized flashing needs to be solvent wiped prior to coating application to remove oil & grease. Bonderized flashing has been treated and doesn’t need the solvent wipe. Copper flashing may be used but copper nails must be used for nailing and care should be taken that no dissimilar metals come in contact with each other. The minimum gauge is 26 but 24 is frequently specified. 2. Flashing should be nailed a minimum of every 3" O.C. with E.G. roofing nails. The flashing should also be tacked to the framing on the vertical leg. 3. A polyurethane sealant should be applied behind every seam or joint and at all terminations. This is very critical at door thresholds and is one of the primary areas of investigation in litigation cases. 4. Flashing needs to be installed prior to door installation and before the building is wrapped. The proper construction sequence is: flashing-lath-stucco-railings-coating. 5. Drain types should be compatible with the coating being applied and need to be spaced to adequately drain the deck. Drains need to be blocked and secured so they don’t move. Drain covers should be installed to help prevent clogging. Drains should be set flush with deck so they don’t create a ponding problem. 6. Scuppers can be used in lieu of deck drains but care should be taken in their location so they don’t drain onto walkways or over doors or windows. Scuppers need to be installed with the flashing and should be installed flat and not tilted upward. They should be sized and spaced to adequately drain the deck. 7. Overflow drains or scuppers must be used when the deck is entirely enclosed. Overflow drains need to be connected to a separate drain line than the main drains. This area is often overlooked. 8. Make sure there is proper ventilation to the deck. Without proper ventilation the deck can be exposed to extreme temperatures during the hot and cold months. C. SLOPING 1. Sloping is a major issue on most projects. The standard is ¼" per foot. Try to achieve sloping in a least one direction in the substrate application. 2. Secondary sloping can be achieved by the coating applicator. A water test should be done to insure correct drainage. 3. In order for the deck to be properly sloped the heights of the doorsill, weep screed, drains and scuppers must be taken into consideration. The ADA act required a step of no more than ½" when entering a door. This is important on entry patios or walkways. 4. Crickets can help divert water between scuppers and drains but it is far more effective to rely on additional drains or scuppers to drain water effectively. Crickets need to be constructed properly and usually extend far back into the deck. This can be a problem on a very shallow deck. If plywood is to be used it needs to be fastened securely and the edge that rests on the deck should be beveled. 5. Gutters and downspouts should be used with scuppers and open drip edge conditions to channel water off the deck and into the proper drainage location. Water from the roof should not be allowed to drain onto the deck as this may overburden the deck drainage system. 1. A pre-job meeting with the architect, contractor, sheet metal contractor, deck coating applicator and coating manufacturer will help to resolve any problems that may exist and will clarify the work that is to be done. Issues to discuss should be: coating type and color, sloping, water test, sheet metal, substrate, warranty and schedule. 2. A job walk with the jobsite superintendent and coating applicator prior to the start of the job should help resolve any last minute questions and scheduling conflicts. 3. The coating manufacturer should be required to make frequent visits to the jobsite. Have them document in writing that the installation is being done according to their written instructions. 4. If there is going to be a long delay where the plywood will be exposed to the elements, a construction coat could be a simple and cost effective way of preventing plywood damage. 5. Water tests are a must over any horizontal deck application. This test will show proper drainage and if there are any obvious leaks. Daily reports help to decipher the daily workings of the job and will be useful in determining what happened on the project. They should contain manpower, material status, weather conditions, areas being worked on and comments about working conditions. 6. A completed job walk should be done with the contractor, deck coating applicator, coatings manufacturer and an owner's representative. This will be used for the owners acceptance of the work and can generate punch lists and help avoid questions about damage to the coating by other trades.
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