Q: What's the best style to install exterior flat-stock trim around a flanged window?

A: JLC Staff replys: The trick to installing exterior flat-stock trim around a flanged window is having the trim sit flat (in plane with the wall) while the trim'due south outer face is proud of the siding for aesthetic reasons. If you just use i-by stock (3/4 inch thick) and rabbet the back inside edge to go over the flange, the edge thickness won't completely cover up nearly lapped siding (such as side-wall shingles that are 3/4 inch where the layers overlap).

The first and near obvious solution is to rabbet 5/4 stock (with a nominal thickness of one inch) for the trim. The first drawback to that method is cost: 5/4 stock is more expensive than 1-by stock. The second problem is the added weight of v/4 stock. It might not seem like much until you accept to carry a agglomeration of large preassembled trim kits up the ladder for 2d-floor windows. In addition, there is the fourth dimension and energy of rabbeting the stock, which typically requires 2 passes on a table saw—easy enough, just the actress fourth dimension adds up.

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To keep flat stock trim in plane with the wall while creating a place for the siding to die into, either rabbet thicker trim over the flange or hold 1-by stock off the wall with a shim strip or stand-off screws.
Tim Healey To go along apartment stock trim in airplane with the wall while creating a place for the siding to dice into, either rabbet thicker trim over the flange or hold 1-by stock off the wall with a shim strip or stand-off screws.

An culling to using thicker stock is installing some kind of backer or shim backside the one-past trim to keep it in airplane while it rests against the window flange. 1 type of capitalist is a thin strip of material attached to the back outside edge of the trim stock. While this method can piece of work well, information technology all the same requires ripping material—nearly probable on a table saw—and then attaching the strip to the trim stock with either glue or tacks or both.

Manny Silva, a frequent contributor to JLC, drives stainless steel pan-head screws either into the dorsum of 1-by trim stock or into the wall merely within the outer edge of the trim. He leaves the screws proud of the trim or the wall well-nigh the aforementioned amount as the thickness of the flange. The big, flat surface of the spiral heads lets them function every bit adjustable stand-offs, keeping the trim in plane with the wall. If you lot try this method, bulldoze the screws every 8 to 12 inches, depending on the flexibility of the trim stock, and use a straightedge to make certain the trim stays apartment.

The easiest and most effective manner to trim a window is to build a "picture show frame" on the footing, assembling the pieces with pocket screws. Bed the trim frame to the flange with a good-quality adhesive caulk earlier fastening it in place with stainless steel nails or screws. If you've used Silva'south stand-off screw method, marking where the screws are located and drive fasteners near those locations to keep from distorting the trim while driving the fasteners.