Q: I plan to wrap some 8-foot-tall porch columns using 1x5 and 1x6 PVC stock, with a small PVC bead applied to the outside corners of the 1x6s. All of the joints will be 90-degree butt joints, and I’m wondering if the column wraps can be just glued together or if the joints should also be reinforced with nails or biscuits. And what kind of glue should I use?
A: John Pace, president and CEO of Versatex Building Products, a major manufacturer of cellular PVC trim, responds: Although it’s not necessary to join the boards together with biscuits, a few 6d stainless steel finish nails or some clamps would be helpful for applying the needed pressure at the glue line to produce strong, bonded joints. If you do choose to use biscuits, make sure that you use ones that are compatible with PVC.
The most important step in the installation process is to use the right adhesive. Sealant-type adhesives are thick and viscous and can be slow to cure. For example, you wouldn’t want to use a polyurethane adhesive, since they are thick and require moisture to accelerate the curing process.
It’s better to use solvent-based adhesives, such as those typically used for bonding PVC plumbing pipe. The cure time is typically shorter, at three to seven minutes, depending on whether it’s a thin or medium-bodied adhesive. Adhesives such as Christy’s Red Hot Blue Glue (tchristy.com) or Extreme Adhesives PVC White Hot (www.royaladhesives.com) are good choices for your particular application. Our company has been fabricating one-piece PVC corners for more than 13 years using Weld-On 705 PVC pipe adhesive (weldon.com) without any issues.
When using these adhesives, apply the glue to only one of the edges that you plan to bond, not both. This will give you the best board-to-board bond. Finally, be sure to allow ample room between the structural post and the PVC wrap for any twisting of the post, especially if the post is wet when wrapped. Otherwise, there is a possibility that one or more of the joints will split apart as the post dries out. To avoid this, take steps to dry out posts before wrapping them with PVC.