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I recently built a deck, and we are looking to make a privacy wall using pencil hollies. As I was making sure weep holes weren’t sitting on joists, it occurred to me that the way that these planter troughs are positioned, the will set between two 16” o/c, 2x8 joists. Each (4) planter will span roughly 6 decking boards and will likely be around 500lbs initially with gravel, dirt, and a young plant. As the plant grows, it may gain some weight as well. Is this a dangerous amount of loading for these conditions?

Side note. I have a plan to route excess water away from the bottom of the planter.

position of planters relative to joists

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    I DK the answer to your question, but have a couple of comments: 1) Do you have any sort of finish on your deck? It looks new. There are many deck finishes out there, I like Penofin (Oops! Product recommendation, sorry!), if you do decide to finish, use a penetrating oil, not a solid surface like varathane. 2) You might want to place some narrow boards under the planters to get them off the deck. That would allow for any rain water that crept underneath to dry out and not rot the deck. May 9 at 15:27
  • It’s treated. I did a lot of research on this and determined that any finish applied in the first season is wasted. I plan on sealing with Thompson’s water seal late this fall.
    – mreff555
    May 9 at 18:15
  • From personal experience, don't let the deck sit too long if you want to it still look "yellow" through the Thompson's, instead of grey. We left ours for a year, and it was quite grey & required a power wash before we sealed it.
    – FreeMan
    May 10 at 14:38
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I've designed and built many decks, and I've looked at a lot of decks that failed. I did some rough calculations, and didn't see any problem with your plan. I'm not sure what kind of plants you have, but I recommend keeping then no taller than 6 or 7 feet.

BTW, looks like a nice deck :-)

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  • They grow to about 6 feet. I’ll trim them if they are getting much taller than that. I think I can get the load down to about 250 lbs per planter by using pumice instead of gravel. That is still ~83lb/sf but it is an improvement.
    – mreff555
    May 9 at 23:37
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Check the code for you area it likely specifies the minimum pound per square foot that a code compliant deck should support (for my area it's 50 pounds per square foot).

Based on a guess of the planter size based on board width my guess is you may have a problem. I'd also note that if you live in an area that gets snow then I definitely be concerned as the holly will hold snow (additional weight) and cause drifting just where you don't want it (yet more weight).

Have you considered the fake outdoor privacy vines you can buy?

Jonathan

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  • I’ll have to look into the local codes and the fake vines. I hadn’t really considered any privacy options until they showed up on the doorstep and wifey said make it work. 🤦‍♂️
    – mreff555
    May 9 at 18:18
  • The uniform load the code provided is the uniform load assumed to occupy the entire deck area, which is to be considered on top of the weight of the planter that, combined, will produce the critical load on the edge beam/joints directly under the planter. The load is to be evaluated based on the layout of the joists/beam, which will require engineer helps, or from someone knows how.
    – r13
    May 9 at 22:14
  • @r13 right. Expected usage + furniture yields an average of 50lb/sf. I’ll make sure nobody sits on the plants.
    – mreff555
    May 9 at 23:41

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