You want your deck to have a sturdy frame and question whether the deck post should be set in concrete for optimal security.
Everyone from contractors to wood companies and professional deck builders said that is a terrible idea. Your deck posts should be attached to the top of the concrete footing but never sitting in concrete.
Read further about why the experts said you shouldn’t place your deck posts in concrete.
Using Concrete for Your Deck Posts
The main problem, according to building experts, with placing your deck posts in concrete is that will cause the wood to rot. It will also eventually cause the concrete to crack.
It may seem like putting deck posts in concrete provides more stability but the reality is it does the opposite and creates a fragile situation. The soil will have some moisture build-up over time and concrete is porous so it will absorb it.
Moisture causes wood to expand and this will end up with the wood rotting and the expansion will cause cracks in the concrete. Your deck posts will need to be replaced much sooner than anticipated and you will also have to repair your concrete footer.
The best and proper way to set deck posts is to set them on top of the concrete and attach them.
Setting Your Posts
One of the main points is to always use pressure-treated lumber for deck posts.
Putting your post on top of the concrete makes for a firmer foundation. You will use a post anchor to attach the posts to the solid concrete footings. Putting concrete footings down first will prevent the wood from rotting because the posts won’t sit directly on the ground.
Setting deck posts require some careful measuring and some patience. The first thing to do is to mark where the deck posts will be. This involves measuring your deck and, depending on how large it is, deciding where the posts will offer the most support.
Large decks will require posts in the middle of the deck as well as the corners to offer a solid foundation. Those who plan on having a lot of weight on the deck, like installing a hot tub, may need to add additional posts and support for that area.
Do the Planning
It’s best to plan out your deck with to-scale measurements before you start setting the footers and deck posts. You need to look to see if the ground is level where all the posts will be.
You may need to grade it or make accommodations for unlevel ground before preparing your footers and attaching deck posts. Preparation will make the actual work go easier and faster.
Preparing the Footer
Concrete footers should be set at least 6 inches below the frost line but the recommendation is 12 inches. This prevents movement when temperatures dip below freezing. Frost lines can be different in every area so you will need to check your area and maybe talk to an extension agent to find out what the frost line is for your home and how to set footers correctly to fit that model.
Dig the post holes for the footers. Once they are dug, you need to add six inches of all-purpose gravel to each hole and make sure it is packed tightly.
Now, take a cylindrical form for the concrete and put it in the post hole. Marke the form a couple of inches off the ground. Pull it out and cut it down to where you marked it. You will need a handsaw to do this.
Set the form back into the post hole with the cut side down. The top should be level and straight.
You are ready to pour the concrete.
Pouring the Concrete Footer
Mix the concrete. Fill it halfway and poke a wood plank around the mix to remove air bubbles. You can fill the rest of the form with concrete after you’ve removed all the air bubbles. Be sure to insert the
anchor bolt into the concrete with an inch of thread visible.
It should be no more than that. Keep everything in place while the concrete cures and use gravel to backfill the surrounding area.
Attaching the Deck Posts
After everything has dried, attach the post brackets, washers, and nuts. Put the pressure plates on top. Put your deck posts on the brackets. They should remain level. Secure them with the structural screws.
This is only the beginning of setting support for your deck. You will still have support beams and joists to attach and some of those will need to be attached to the deck posts.
Can posts sit on concrete without anchor brackets?
No, posts must sit on and also be anchored to concrete footings to be safe and be able to handle different types of weight. Proper footings for decks don’t include pre-cast concrete piers or patios. You must use a post-base connector to anchor posts to concrete footings.
Can I use No More Nails to stick wood to concrete?
This product is a reliable adhesive and can be used on heavier construction materials like wood and concrete. While it holds instantly and is a good product, it isn’t a substitute for anchors.
You can use it as supplemental security to help your deck post adhere to concrete, along with anchors. However, you must still actually use brackets to anchor your posts for utmost safety.
How long will pressure-treated wood deck posts last?
Wood, including pressure-treated wood, will last from 10 to 15 years. Industry experts give other products like capped composite boards a longer life with that product lasting up to 30 years.
Final Thoughts
Understanding why you must attach your deck posts to your concrete footers rather than insert them is the first step. Can you insert your deck post into concrete? Yes, that is away. Should you concrete your deck posts? No.
It takes a little extra work to attach them. However, that extra couple of steps will help your deck posts and concrete footers last a lot longer because it eliminates significant moisture issues.
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