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Roof Assembly | Flashing Details | Coating Rate Chart

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UK5 KraftFelt Separating Sheet
Roof decks that may allow asphalt to migrate through the deck require a nailed or stapled separating sheet of UK5 KraftFelt attached to the deck. The KraftFelt shall be installed as the first layer, and as a separating sheet between the deck and the mechanically fastened base sheet or insulation. Fasten the KraftFelt with minimum side laps of 2" and end laps of 6" offset at least 36".

Fields Asphalts
Correct asphalt application temperature or viscosity shall be maintained so as to preserve the quality of the asphalt and so as to ensure thorough lamination of the reinforcing sheets. Overheating or maintaining asphalts at elevated temperatures will damage the asphalt as well as create a fire danger.

In order to maintain the correct application viscosity for ambient applied cutback asphalts, the applicator shall employ equipment to maintain the cutback asphalt at a minimum of 110° F when measured at the point of application.

Required Guidelines for Heating Asphalts
1. Heating equipment temperatures shall not exceed 120° F for ambient applied asphalts.

2. Heating equipment temperatures shall be maintained at less than 25° F below the flash point for hot applied asphalts.

3. Asphalt shall not be kept at high temperatures for prolonged periods.

4. Asphalt shall not remain in open rooftop containers for long periods of time.

5. Pipelines shall be insulated to aid in maintaining the correct asphalt temperature on the roof.

6. Asphalt shall be circulated while it is heating.

In order to maintain the correct application viscosity for hot asphalts, the applicator shall follow the correct EVT (Equiviscous Temperature) guidelines. EVT is the temperature at which hot applied asphalt has the correct viscosity for installation of the roof system. The EVT range is 25° F above or below the EVT, thus giving a maximum range of 50° F. The EVT application temperature range is measured in the asphalt mopping cart or machine spreader at the time of application. The EVT for hot asphalt is as follows: For cart applications 125 centipoise; and for machine applications, 75 centipoise.



Asphalt Application

Asphalt application includes the correct rate of speed at which the asphalt is applied as well as the method of application such as by brushing, squeegeeing, mopping, spraying, or machine application. Heated asphalt better penetrates and fuses with the asphalt in the reinforcing sheets, which better laminates the sheets together. Correct application temperature is vital for the construction of a quality, well-laminated roof system membrane. The correct asphalt temperature must be maintained in order to ensure good lamination of the sheets during application.

Temperature affects the viscosity and flow characteristics of asphalt, and therefore, the weight or application quantities. Temperatures that are too high can result in asphalt that has low viscosity and greater flow characteristics when applied, and thus can cause:
1. Lighter asphalt weight applications

2. Incomplete asphalt coverage

3. Asphalt voids between reinforcing sheets

4. Diminished asphalt waterproofing qualities.

5. Reduced asphalt weathering durability

6. Project site safety hazards

Temperatures that are too low can result in asphalt that has high viscosity and lower flow characteristics when applied, and thus cause:
1. Heavier asphalt weight applications

2. Poor adhesion

3. Inadequate lamination of sheets

4. Slippage of the reinforcing sheets

5. High expansion properties

6. Low asphalt tensile strength

Base Sheet Installation
The base sheet layer shall be started at the lowest point of the roof deck such as at a drain or downslope perimeter edge. Base sheet side laps shall be a minimum of 2", leaving an exposure of 34" for 36" base sheets and 38" for 40" base sheets.

Nailing pattern for mechanically fastened base sheets
To mechanically fasten the base sheet, nail the seams and ends 9" on center. Also, stagger nail two rows 18" on center and 12" distant from each edge.

Installation of Base Sheets
Install 1 layer of base sheets, adhering the base sheets to the substrate, except when installing the base sheets directly to nailable type decks, which require mechanically fastened base sheets. Adhere an extra layer of base sheets in valleys and waterways prior to installation of the ply sheets. Extend the extra layer of polyester base sheets a minimum of 12" up inclines.


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2240 Taylor Way,
Tacoma WA 98421

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