Installing 4x4s - Concrete? Spikes?

[7L Farm]

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First question, have you figured out what post support specs you NEED for the deck you're planning. (I.e. are your current 4x4 posts enough, at their existing spacing, or do you need additional 4x4 posts or larger or what). It depends on the deck size and load.

IF your problem is simply that you want to put a deck beam on top of the existing 4x4 but also want that existing 4x4 to stick up further, here are your most obvious (good) choices IMO:

Either attach a STRONG WELL-MADE chock on the side of the existing 4x4 (meaning, at least a coupla feet long and attached with a bunch of good large p/t-compatible fasteners throughout its length) in order to put the beam on, and also bolt thru beam+4x4;

or alternatively, lop the existing 4x4 off at desired level, put the deck beam atop it with suitable hardware or wooden chocks to keep it from slipping off, then sister in another piece of wood (it could even serve as one of the wooden chocks in this case) that extends upwards to support your upper run fencing or deck railing or whatever.

But you GOT to make sure you have the engineering of the deck figured out first... don't just eyeball-and-guess. There are tables you can look at for these things, look up what deck size and span and so forth and it will tell you what sort of post support options you can get away with. Look in good "DIY deck building" books, or I would think that google could turn something up online.

Good luck, have fun,

Pat

If you look at the above picture you will see 3 post that stickup. I didn't put the 4th post in because I didn't think about putting a deck up there.Now, I've decided on a deck. Now, I need to add the fourth post. The problem is where I need to put the post there's already one there that's to short & is cemented in the ground. It's gonna be like a tower not real big. It will be like 6' x 9'. I'm gonna run 2x6 on both sides of 4x4 long ways & then run 2x6 on top. I guess I'll just through bolt a 12' 4x4 to the fourth pole. I'll drill three holes thru both 4x4's & bolt them together. It won't be square but should still be strong enough to hold a few folks on top.

 

[patandchickens]

Ohhhhhh. OK, gotcha. That tall? Wow, you really need to think about the engineering here. Be kind of dicey having that on just four 4x4 posts even if the total area is small; at the very least you want REALLY GOOD diagonal bracing in all directions. Seriously. Given how far you will have to fall if this thing goes over or comes down, I would suggest checking your gut impulses with some actual construction tables.

As to your problem not the cheapest but the simplest/most-secure solution is indeed to sister in a whole nother post onto the too-short one. Set the new post on the concrete around the existing post. Personally I would be inclined to use 2x8s on both sides and a whole lotta spikes (holes predrilled too-small, not just hammering into the virgin posts) to attach the two together. But you could use a few carriage bolts instead or something like that. Remember p/t lumber is very 'splitty' so predrill things carefully, you really don't want to make longitudinal cracks in either post.


Pat

 

[7L Farm]

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The platform will probably be about 9' up.The joist will be 2x8 running long ways on both sides of the 4x4's long ways & the deck will be 2x6 all wood is treated & I'll use 3 inch screws. I'll just butt the longer 4x4 against the short one & drill holes thru both 4x4's & use a 5/8 inch bolt with washers on both side. Probably use at least three bolts. I think it will be plenty strong.

 

[jgaepi]

I actually discovered this at the hardware store yesterday and then another person here suggested I check this thread out. I would agree that this system is not 100% as effective as concrete. But concrete is nasty and mostly permanent. My thought is to install this parallel to my permanent wood fence, about 4 feet away, and then a perpendicular 2X4 cross beam either at the top or bottom to the permanent fence for stability. Then use steel stakes every 4 to 6 feet with chicken wire for about 24 feet, and then place another at the opposite end. This would allow me to frame entrance doors at each end and create a little bit of stability down the line to help the steel stakes. Also ... I have to work around landscape pvc piping and this would allow me to avoid concrete and create a situation down the road where a pipe could crack and then I have limited access to repair. Any thoughts?