How to Anchor Deck Support Posts Where There Is A High Water Table?

by Monica
(Canada)

We are putting in an above ground pool and wish to put a deck and pergola around it. Our problem is we have a high water table. About 6' below ground.

Our neighbor recently built his deck on blocks but I am worried it will shift.

Especially since we wish to also build a 14' x 18' pergola structure beside it. We are in a cold climate area. Any suggestions?

Concrete deck blocks are an obvious first thought but they don't provide and anchoring to the soil nor do they secure the deck to the blocks.

It is all totally resting there by virtue of the decks weight. In some cases this is fine. But in other situation as you have just mentioned it is not desirable.

What To Do?

If you can dig a footing because you are concerned about the water table affecting the footings then you are left with spike or helical anchors.

Spikes are hammered into the ground and are a lot of work to install. Also most of them do not have a load plate do distribute weight so you have to use a lot of them to spread the weight around and not over load the soil.

Helical piers that are engineered are fantastic. But they are at least $250 each and often more. This could cost a lot of money as above ground pool decks usually need dozens of footings.

There are some helical piers that you can screw into the ground with two people using a 4x4 and walking around in circles about thirty times. Try doing that and see how much fun and work that is.

Or you can use the Titan Deck Foot Anchor which does very well for above ground pool footings. It installs with a hand held electric corded impact wrench. The footings can be driven in or retracted easily to find the right location.

Your footing is securely connected to the soil and your deck is securely connected to the footings. Very secure and stable.

However the entire system floats on the surface of the soil. So if the soil expands 1/2" in the winter because of frost the entire deck will rise with it and settle back down again in the spring.

You must leave a 1" gap between the decking and the coping of the pool to accommodate this annual movement. But the cost and time savings are huge.

You should read more about the deck foot anchor and see if it is right for you.

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