Synthetic Stucco Without Failures

When applying a liquid waterproofing membrane over OSB or plywood sheathing, start by sealing the panel joints with a sandwich of fiberglass mesh and the liquid membrane.

Mesh and sealant should be applied to all inside and outside corners. A brush can be used to work the membrane into tight spots.

Here's another example of an outside corner being sealed with liquid membrane and mesh, followed by another layer of liquid membrane.

Roof-to-wall intersections see an enormous amount of water, making these critical areas to flash well. Step flashing should be woven in with the roof shingles, and then a counterflashing installed to protect against water getting behind the top edge of the step flashing.

At the roof's bottom edge, sidewall flashing must terminate with a kickout to deflect water away from the sidewall and into a gutter. Large, preformed kickouts are preferred for steep roofs.

Shallow roofs don't require as big a kickout as steep ones do.

Apply a layer of mesh and liquid WRB to the top edge of the step flashing (shown) and to the top of the counterflashing.

A cricket in the plane of the roof creates positive drainage away from the chimney. Use plenty of peel-and-stick on the cricket, lapping it onto the chimney and sealing its top edge with mesh and a liquid WRB.

A liquid WRB can be sprayed on or rolled on. Spraying is faster, but rolling is easier to control.

Through-wall flashing is needed at the transition from stucco to another type of siding, be it synthetic stone, vinyl, or fiber-cement. In this project, W.R. Grace Perm-A-Barrier wall membrane (the green membrane at the base of the wall) was used. The top edge of the through-flashing is adhered to the wall and sealed with mesh and liquid WRB.

After the liquid WRB is applied, windows and doors are installed. Apply mesh and liquid WRB to the nail fins on the head and side jambs, but leave the sills open to allow water to drain out.

Again, the sills are left open while the side and head jambs are pasted over with mesh and liquid WRB.

The layer that most often gets missed in a DEFS assembly is the drainage layer. You can use a rainscreen material for this.

The rainscreen forms a three-dimensional separation between the WRB and the base panels that will be installed over it.

The DEFS base panels, which replace the insulation panels of an EIFS assembly, are installed over the drainage layer.

Control joints are fashioned by spacing the base panels 1/2 inch apart ...

... and by installing a vinyl strip that will accordion in and out as the wall swells and shrinks.

Vertical control joints should completely divide the wall section. Bring the joint right through any transition at the wall base.

Horizontal control joints are typically placed between floors along the second- (and third-) floor band joists.

Where a horizontal joint intersects a roofline or bump-out, integrate the control joint with edge treatments at the base of a wall.

A vinyl J-track, or casing bead, is installed at the base of the wall to receive the base panels. It has weep holes that allow water to drain out, and it functions as a screed when the stucco base coat is troweled on.

Outside corners should get a corner bead to create a crisp edge to define architectural details in the facade.

The base panel should finish out at least 2 inches above a paved surface or above a sloped roof.

An EIFS system would typically include an impact-resistant mesh over the entire surface of the foam boards. With DEFS, mesh is applied only at the joints, to help prevent the panel edges from telegraphing through the stucco. The mesh is embedded in the base coat of stucco.

Once the base coat has cured, foam trim is applied 3/8 inch away from the edge of windows and doors.

The foam trim then gets a base coat. The channel between the foam trim and the window is later sealed with backer rod and caulk.

When the backer rod and caulk are installed around the windows, the sealant needs to adhere to the backwrapped edge of the preformed foam trim, but not to the finish coat, to prevent contraction of the sealant from causing the finish coat to separate from the base coat. The tape securing the poly that protects the windows gives a crisp edge to apply the sealant to, free of any finish topping.

The beveled transition to the stone base is built up with layers of EPS.

The beveled EPS base will be covered with the stucco base coat.

An acrylic latex is used to finish off the stucco.

The finish coat can be sprayed on.

After the latex acrylic is applied, it is worked with a trowel to achieve the desired texture and finish.

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