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4x4 post on existing deck

What is the best way to mount 4 x 4 posts on an existing concrete deck without cutting the concrete?

A. Spruce
Re: 4x4 post on existing deck

What is the purpose of the post?

If the post will have structural stability from the structure it supports, then a post base can be attached to the surface of the slab, providing that the slab can support the weight of the post and structure combined. If the slab cannot support the weight, then the slab must be cut so that a proper footing can be installed to support the post and structure.

If the post must have it's own structural stability, then the only way to do that is to bury it in the ground. Cut a hole in the slab, dig the hole, plant the post in concrete, then finish the concrete to match the slab.

Re: 4x4 post on existing deck

The post above was correct with best intentions, but didn't answer the question.

Like the above poster stated, if your concrete floor is stable you can fasten your 4x4 post with electro-galvanized post brackets. You can buy them at any home center near you. Simpson 4x4 post brackets are what you need and tapcon concrete screws.

Good luck!

A. Spruce
Re: 4x4 post on existing deck
Deckbuilder wrote:

The post above was correct with best intentions, but didn't answer the question.

With all due respect, without knowing what the specific purpose of the post is, there is no way to give a more complete answer.

The post base you suggest is only applicable if the post is receiving it's structural stability from what it supports, such as a car port, patio cover, or arbor. It is not suitable for things such as a railing, fence post or any other purpose where the post must be structurally self supporting.

Additionally, a "stable concrete floor" may or may not be adequate, depending on the weight and design of the structure being applied. For a lightweight arbor, maybe a post base would be fine on a standard 4" slab (assuming the slab is actually 4" ), however, much more than that and a proper footing is needed to support the weight and the wind loads placed on the structure.

Re: 4x4 post on existing deck

I'll tell you what I did when I built a railing for my sea wall on a concrete slab above.

I drilled into the concrete starting with small, then moving to larger bits. I then insert my anchors, tightened them down until they grabbed, then removed the nut. I then drilled into the bottom of the 4x6 post (in my example), then into the side..much like you might see one put together a railing for a staircase. I had to square off the bore in the side to take a washer and nut...making it large enough so I could tighten it down. I then put some construction adhesive on the bottom of the post, placed the post on the anchor, placed the washer and nut, then tightened it down. You would be surprised how strong that railing was and still is today.

I went with a 4x6 so there would be more surface area. I think that helped.

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