GW 1-2

BUILDING EXPANSION JOINT COVERS

Gaco Western Field-Curing Neoprene Sheet Expansion Joint: Where maximum conformity to irregular substrates (sprayed-in-place urethane foam, concrete block, etc.) is required use NF-621.

Note: Standard NF-621 is black and will discolor light colored top coats.

SEALING OF CRACKS AND CONSTRUCTION JOINTS, SUBSTRATE CHANGES AND FLASHING

See Architectural Details GW-5-D2 and GW-5-D1.

This step, which follows priming and precedes body coating, is the most critical stage in the application of GacoFlex liquid roofing. Success or failure in application of this system depends largely on the care with which reinforcement tapes are applied and sealed. The surface should be watertight at the conclusion of this step.

The following treatments should be used:

Working Cracks, Concrete

These are joints or cracks which have moved or will move appreciably due to thermal changes or vibration. They include contraction joints such as those described in Section GW-2-1. A crack that extends at each end to the edge of the surface, to a building expansion joint or to another working crack may be a working crack. A crack with minute broken fragments along the edge is probably a working crack - working cracks move in any or all of the three dimensions. Treat these cracks in one of the following two ways:

1. Gaco Western 66B Tape System: 66B is a polyester spunbonded joint, crack and flashing tape.
2. Gaco Western Neoprene Sheet System: This is thicker than the 66B system and, therefore, much more visible.

• Note: Do not use field curing neoprene sheet on deck applications subject to auto traffic. This sheet is sufficiently soft that it can be damaged while curing.

Non-moving Cracks, Concrete

Suitable for hairline cracks only. Apply a stripe coat centered over the crack. The crack must be fully sealed.

Substrate Changes, Changes of Plane and Flashing

Tape reinforcement is required at changes in substrate material. It is also required when the substrate changes plane in a valley, or a crack exists at other changes in plane.

1. Roof Jacks, Metal Flashing: Use 66B System with 4" (10 cm) tape.
2. Flashing at Parapets, Curbs, Ventilators, Skylights, etc.: If the substrates can move differentially, use the neoprene sheet flashing systems. Otherwise, use the 66B system with 4" (10 cm) tape so that the flashing extends at least 2" (5 cm) above deck level unless a different height is shown in the drawings.
3. Flashing at Pipe Penetrations: See Installation Detail GW-5-D4.
4. Flashing Compound: Apply caulking to any vertical voids behind flashing such as mortar joints. It may also be used in lieu of other flashing at thresholds too low for application of tape. The fillet must be continuous, pressed firmly in place and overcoated with a heavy coat of base elastomer.

Joints in Plywood

Joint Treatment: Use the 66B taping system over supported joints on the same plane, supported joints at changes in place, or unsupported joints.

Notice: Where enhanced appearance of joint area is desired, sand and fill voids, joints and nail heads. Use caulking, epoxy grout (see GW-1-1) or single package urethane.

There should be a 100% inspection by the applicator's foreman and the architect after completion of this stage.

Defects in taping and flashing must be corrected prior to proceeding with base coats.