New concrete patio with lean-to roof on posts
I’m building an 8×16 concrete patio with a lean-to roof over it. What is the proper way to ensure the slab and piers for the 6×6 posts interact properly? There will be three posts in the front of the patio. Dig and pour three piers for 6×6, pour patio on top of piers, and then attach posts to top of slab? Or pour piers to finished slab height and pour slab around piers?
Replies
Depends on where you are and the frost depth.
If you set the piers so they extend below the frost line, and the slab is not so isolated from frost heave, the interface will move.
That's correct, the piers will be below the frost line (pennsylvania)
If this is just a slab on ground without perimeter foundation walls, the one should always anticipate some amount of differential vertical movement over time. It's always better to have the top of the pier finished nice slightly about the slab.
Further, if your patio slab will wrap completely around the pier(s), one should install a compressible joint filler between the slab and the pier(s). This will help avoid slab cracking as the concrete shrinks during hardening.
For your patio project, it's best to pour the piers to the finished slab height and then pour the slab around them. This way, you ensure a solid connection between the slab and the posts.
Dig and pour the piers first, then pour the slab, making sure it's level with the tops of the piers. Once the slab is set, you can attach the 6x6 posts securely to the top of the slab. This method should give you a sturdy and well-integrated patio with a lean-to roof.
For your setup, it's best to pour the piers first to the height of the finished slab, then pour the slab around them. This ensures a solid connection between the posts and the slab, giving your patio the stability it needs. Plus, attaching the posts directly to the slab afterward is simpler and saves you from any potential alignment issues.