The challenge: How to replace decking under gazebo!

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Old 01-18-18, 12:57 PM
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The challenge: How to replace decking under gazebo!

Hello guys you have been very helpful in the past. Here's the latest challenge. I have updated my upper deck to all composite deck boards and rails. I now want to replace the deck boards that my gazebo is sitting on with composite. I am confident the pressure treated joists are fine. The gazebo is about 5 feet off the ground on cedar planks. The ends of the planks outside of the gazebo are rotting. There are 8 gazebo posts sitting on top of the planks I want to replace. The posts are essentially 4x4's. The railing between the posts is not really structurally strong, just screwed into the posts with some short deck screws. In pretty much all situations, there are 2 gazebo posts sitting on a single deck board! How can I get these deck boards out from under the posts, replace the deck board with a composite board, and lower the posts back onto the new deck board? Also somewhat compounding the problem is the fact that the current deck boards are 2x6's and the new deck boards are basically 1x6. Attached are some photos that I hope will help. All input is appreciated!
 
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Old 01-18-18, 01:05 PM
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Old 01-18-18, 01:08 PM
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Old 01-18-18, 01:11 PM
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Seems like the easiest thing to do is remove the metal post bases, cut the old decking from around each post as close as you can, then knock out whatever residual board is remaining underneath. Maybe you'll get lucky and there won't be any nails positioned under the posts. If there are, you can cut the nails from underneath using a reciprocating saw, then tap the old boards out. Prior to doing so, temporarily support the post by bracing the roof above to take off the load so it is easier to remove the old boards and slide the new decking underneath. You could use a floor jack and 2x4 stud with short piece nailed on top in a 'T' shape positioned under header to jack each post up slightly. This may or may not be necessary considering there will be 7 other posts at any given time supporting the structure. Try one without bracing first and see what happens.
 
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Old 01-18-18, 01:12 PM
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Old 01-18-18, 01:29 PM
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You could use a floor jack and 2x4 stud with short piece nailed on top in a 'T' shape positioned under header to jack each post up slightly.
Rather than doing one post at a time, I would place the jack between two posts since that will keep the jack out of your working area and you'll have a straight piece of header above to support.

Also, I'd replace one or two boards at a time so you have a floor surface to work on while you progress.
 
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Old 01-19-18, 08:21 AM
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Thanks for the reply Mossman. When you say "floor jack", do you mean a hydraulic car jack, or scissor jack, or something else? And when you say "header", do you mean the bottom of the roof, between the posts?
 
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Old 01-19-18, 08:24 AM
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When you say "floor jack", do you mean a hydraulic car jack, or scissor jack, or something else?
A hydraulic jack is what I was referring to. If you don't have a jack, you could also just make the temporary support slightly taller than the bottom of the header and wedge it in place. In fact that would be easier and safer IMO. You don't need to worry about scratching the decking because you are tearing it out anyhow. If it were new decking and you were replacing the posts, I would use a jack. Place the top of the support under the header first, then tap the bottom with a hammer until nearly vertical. Don't go overboard--the goal is to support the roof and take the load off the posts you are working on, not to lift/raise the roof. 1/8" or so is probably fine. When you're done with each side, tap the bottom of the support the opposite direction to remove it. Looks like you'll need to remove your screens to do so.

And when you say "header", do you mean the bottom of the roof, between the posts?
The headers are the pieces of lumber (likely 2x10s) that span between each set of posts and support the roof rafters.
 
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Last edited by mossman; 01-19-18 at 08:44 AM.
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Old 01-19-18, 11:45 AM
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Very good insight Mossman and thanks for the diagram!
 
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Old 01-19-18, 12:06 PM
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Sure thing. Please post back with outcome. Good luck.
 
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Old 01-19-18, 12:22 PM
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Not advocating one way over the other as this a job I would probably turn down as there is an element of "collapse" involved. Given that, I'm not sure a single jack point is going to do much for you. If a single jack point, the jack will most likely be bearing on the same boards you are trying to remove (if that makes sense). Therefore, in my mind, multiple jack points would be more in line with taking the weight off a span of boards to be able to initiate the repair.

I would also want to know a little about the framing under the deck and where the gazebo falls on that mix. Composite decking is not structural and is not designed to carry loads like that. It would more than likely need to have the full bearing load transferred down to footings for support.
 
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Old 01-19-18, 01:15 PM
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If a single jack point, the jack will most likely be bearing on the same boards you are trying to remove (if that makes sense).
You'd need to position the jack/support strategically, but I believe it can be done without resting the on the boards that are being removed. For example, jack/support in the red areas and you'll be fine.

Didn't think of the load bearing properties of composite though. Maybe you're better off replacing the boards with wood and staining them to match the existing composite.
 
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Old 01-19-18, 02:59 PM
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Is cutting the decking around the post and just leaving that piece of decking in place an option, assuming there may need to be some blocking done to add the new?

Would be interesting to see the framing!
 
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Old 01-19-18, 06:10 PM
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Anyone can come up with a plan to raise the gazebo to replace boards. But based on the pictures provided there is insufficient support for the composite to carry the loads after the deck it reset, All posts of the gazebo need to be on structural members of some sort. With 2 by material, it will transfer the loads to the next member as part of the structure of the deck. Composites on the other hand will not provide that integrity.
 
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Old 01-20-18, 07:05 AM
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From what little of the framing I can see in the first photo, it appears that the structure under the gazebo is pretty beefy. Assuming it is adequate, is it still not a good idea to have a piece of composite sandwiched between the post and beam/joist underneath? If not, then could the OP put small blocks of PT under the posts and butt composite up against? Except I imagine that does nothing for uplift and he'd want to secure the post base to the framing, not the decking.
 
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Old 01-23-18, 06:30 AM
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Hmm, very good insight guys, I also had not considered the weight of the gazebo posts onto the composite boards.

The structure of the gazebo deck is very sound with 2x8 pressure treated joists 16" on center. However, if a gazebo post rests between 2 joists, I don't think the composite boards would carry the load.

Possible solutions are to add joists anywhere the posts are not on top of a joist, or use 2x8 blocking between joists. Thoughts on that?

Someone asked if the 2x6 cedar planks under the posts could be cut around and kept. A few could, but some of the posts are near the ends of the deck board where there is some element of rotting.
 
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Old 07-19-18, 05:45 AM
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Hello, I wanted to give an update on this project. A friend of mine suggested that I shore up the gazebo railings by adding more screws to them, then lift one post of the gazebo at a time using a board as a lever. I did this by attaching 2 boards together with a hinge so the lever could pivot. I put a scissor jack under the vertical board. Attached is a picture.
 
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Old 07-19-18, 05:52 AM
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Before setting the posts down on the new composite decking, I added double 2x8 cross joists or blocking under every post between existing joists. This gives strength to the composite boards.

Here are some pics of the final product. THANKS EVERYONE FOR ALL THE HELP!
 
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