Q. We bought a house with a deck and didn’t know it never had a permit until we went to make a home office out of the garage. We then learned that the deck posts are resting on the patio, with no footings in the ground, so the deck won’t pass an inspection. The problem is that we got estimates for the concrete posts, 3 feet deep in the ground, and it’s going to be a lot more than we expected, like $12,000. We decided to take the deck down instead, but then we saw that the crumbled concrete steps underneath have to be replaced. Between demolition costs and new back steps, we feel stuck. Any alternative ideas would be greatly appreciated.
A. Once again, an avoidable problem created by someone not investigating the right way, before building, then passing the problem on to an innocent buyer. An engineer’s building report before buying might have caught this problem, but like many other instances, the problem is pushed off because it seemed like a minor reason to not buy the house.
The building code requires the support posts extend into the ground in your region at least 3 feet deep, so the post bottoms are below the front line. This is to avoid uplift that causes damage when the ground is frozen in the colder months. Ice crystals form that crowd out the posts and force them upward. Resting on a patio, not only is the deck moving up and down with the slab, but it has no safe anchorage to resist high winds from ripping it to pieces. So now you need an anchorage management class before you get too upset.
A publication on barn-building for the farming industry, mostly in the American Midwest, often publishes techniques with many cost-saving engineering diagrams and discussions about using treated wood posts, coated or uncoated, extending into the ground and resting on thick rubber disks down below the 3- to 4-foot-deep frost line. The discs come in sizes from 12 inches to 36 inches in diameter, to spread the loads, which must be calculated to select the correct-sized column base footing pad.
The same requirement of flared-out spread is required in the building code for concrete posts and must be calculated, no guessing or shortcuts allowed, and there actually are code tables outlining the minimum required spread size of column bases. This technique, without concrete, was developed to save money and time. If you can imagine the constant stresses and strains the wind and earth can impose on a freestanding barn in a Midwest blizzard, you can imagine that the person who came up with this idea must have been outstanding in their field.
Since you will need plans for the deck to show this money-saving solution, hire a licensed professional who will review the code, the right method and save you much more than the cost of their service. You can already see what guessing led to. Good luck!
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