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Siding & Exterior Trim

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Mastered in a Minute

How to Trim an Exterior Window

Measure, cut, and assemble window casings ahead of time to make installation fast and easy.

By Andy Engel, Justin Fink

Here’s a method for creating good-looking exterior window trim quickly: Assemble the pieces to form a frame, then install the assembly as a unit. Make a pitched sill from 6/4 stock, rabbet the backs of the legs and head to fit around the window flanges, then fasten the pieces together with a combination of pocket screws and self-drilling screws. Once the frame is installed around the window with trim screws, caulk the 1/8-inch gap between the window and the frame.

For more information on this topic:

Boral Siding and Trim: A Deeper Look — The exterior of this FHB House is finished with a low-maintenance siding made from coal fly ash, polymers, and glass fibers.

Dressing up Stock Windows — New windows may be energy efficient, but they often lack interesting trim details. This short article shows how to beef up exterior window trim with commonly available materials.

Trimming the Windows — Here’s a technique for using pocket screws to assemble pieces of Boral TruExterior trim for a window.

Exterior-Trim Details That Last — A restoration carpenter explains how to use foam backer rod, caulk and nylon-filament erosion mat to protect exterior trim from water damage.

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Previous: How to Install Exterior Window Trim Next: Prefabricating Exterior Window Trim

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Siding & Exterior Trim

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Installing Exterior Trim

View Comments

  1. weaselfoot | Mar 07, 2016 03:55pm | #1

    Interesting and helpful! I have heard of buying PVC in board form!

  2. weaselfoot | Mar 07, 2016 03:59pm | #2

    Sorry - Sentence should read "I have NEVER heard of buying PVC in board form!"

  3. SRQ_Sid | Mar 07, 2016 07:44pm | #3

    It seems that if PVC was applied at 90 Deg.F and the winter temperature dropped to -10 F an eight foot long piece might shrink 1/4" and squeeze out the caulking. Has that been observed in practice?

  4. user-5256713 | Aug 07, 2016 07:47am | #4

    just what i needed and will give it a try. I don't think i will paint as I won't have many exposed cut ends or exposed holes

  5. donaldwong156 | Mar 02, 2017 05:32am | #5

    nice video

  6. user-6758414 | Jun 08, 2017 09:34am | #6

    Can anyone help with where you would find 6/4 pvc trim board?
    thanks

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Siding & Exterior Trim

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