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View Full Version : building a shed with smartside vertical panels and azek trim



tim vadas
07-11-2019, 9:56 PM
I'm in the middle of building a shed and didn't think too carefully about the trim boards. I was planning on using azek (cellular PVC) for trim around a couple doors and windows. The smart siding installation instructions say to install flashing over window and door trim and leave a 3/16 gap. All the videos on youtube that show people building sheds with this stuff have them just nailing/screwing the trim in on top of the siding. Installing trim first, then cutting the smartside panels to fit around them is a pain in the a$$.

I'm assuming if i want it to last, i should install the trim first, with the flashing. I'm just worried about cutting the panels to fit exactly around a window. Any tips for ease of doing that or just trust my measurements and make sure the framing is all square.

Imran Malik
07-11-2019, 11:35 PM
I am not a builder but am currently working on a large room addition with windows and smart siding. I am using the Dutch lap horizontal SS. Anyhow, I flashed the window RO and installed windows. At this point, it does not matter what goes first, trim or siding. I installed trim first so I know how long to cut each board and maintain 3/16 gap. In your case, you can cut your panel, verify gap, install it first or after trim. I used Festool saw and guide for long rips and do not recall using jigsaw but cannot imagine any issues with either. So easy to fine tune the opening in the panel. Hope this helps.

Rick Potter
07-12-2019, 12:52 AM
I just had a garage built using LP Smartsiding. We put the siding up first, and used redwood trim. The old workshop next to it was built this way over 30 years ago, and still looks fine. Smartside may not have existed then, but we used a particle board product that sure looks like it, except it is thicker.

The old one was painted when new, and repainted 12 years ago. It will get another coat, just so the paint matches the new building. When we get finished, the old workshop will keep it's original siding, and be flanked on one side by a connected new garage, and on the other side by a new 500 sq. ft. Casita for a family member.

One thing to keep in mind is that we do not live in a snow area.

Jim Becker
07-12-2019, 8:48 AM
For products like cellular PVC, expansion/contraction needs to be taken into consideration as they often move a lot more than wood products with temperature swings. That may be the reason for the installation instructions from your siding manufacturer. Yes, it takes more time to carefully cut to allow for this, but that's better than something buckling. Trust me, I have Azek trim in some areas of our addition that have been problematic because of expansion/contraction. My general contractor friend has since switched to a different product (more than once) that has a lower expansion/contraction rate.

Lisa Starr
07-12-2019, 11:29 AM
Azek does have a large expansion/contraction rate, but can be greatly minimized with appropriate fastening and details. Our entire home has Azek trim fastened with trim screws that are long enough to have 3/4" minimum penetration in the framing. Additionally, the recommended # and spacing of the screws is a must. We used 1/2 lap joints in a 30' long frieze board with those methods and find we have about 1/8" gap at each of 2 joints in the coldest weather and no buckling in the hottest.