Installation Note: All trim in the article, Installing PVC Trim, is Azek PVC trim. All miters were glued ~ Expansion joints are located on the inside [house] butt ends and under cover of overlapped boards and concealed with flexible caulking.
PVC Trim – What You Need To Know
Many customers these days are requesting that I use a PVC product to replace rotting wood. In these cases I recommend and use Azek trim boards.
My local lumber yard, Concord Lumber, stocks most of the sized I need and I glue up and make any specialty moldings or sizes that they don’t stock.
Azek is a great wood replacement choice non-stress application. The beauty of this product is that it cuts, drills, routs and fastens the same as wood.
However, there are a few considerations and procedures that should be followed when installing pvc trim to allow a quality installation. Many contractors are not aware or do not follow these steps.
Fastening:
1. Do not use finish, brads or staples. Fasteners MUST have a head.
2. Fasteners should penetrate the wood substrate a minimum of 1-1/2”.
3. The best fasteners I’ve seen are the Cortex [concealed fastening system] and are made by Fasten Master. This system has a special screw adapter that sinks the screw at the correct depth to receive a PVC plug. It’s real nice system and conceals the fastener heads without caulking, sanding or painting.
4. Install fasteners no more than 2” from the end of boards.
5. Install 2 fasteners for boards less than 12” wide. Wider boards require more fasteners.
6. Install fasteners every 12” to 16” o.c.
Glue
1. Glue joints and secure with a fastener to prevent joint separation.
2. Use AZEK adhesive – it has a 10 minute working time and is fully cured in 24 hours.
Expansion and Contraction
Here is where many contractors fail to follow the installation rules. There is nothing worse than getting a call back a year later because trim boards open up 1/4″
1. AZEK does expand with temperature extremes and moves differently than wood.
2. A general rule of thumb is that AZEK will move 1/8” per 18’.
3. When installing long sections, such as 100’ fascias, consider using a solid sub fascia and construction adhesive and fasteners to reduce movement.
4. Installing and gluing one joint tight and allowing 1/16” on the other joint to move is another option. This joint can be ship lapped to hide the movement or cut as a scarf joint and then caulked with a flexible caulk.
Painting
1. AZEK does not require paint but using a 100% acrylic latex paint with Light Reflective Value [LRV] of 55 of higher will help reduce movement.
2. Darker color paints should have a Vinyl safe coating.
