Deck Footings and Depth

As warmer weather is hopefully on its way many people are in hardware stores, and big box retailers looking for deck plans, materials, and estimated costs, but don't forget the last installment in my blog for decks. While posts and footings may not be the most interesting thing to talk about, this does not negate their extreme importance. Deck footings are an extremely important part of your decking system because this is an area of your deck that supports load or weight, and not just dead loads, but live loads. When you, and your family and friends are on your deck it must be able to support the load of the deck and everything contained on it. Not only does your deck have to support you and everything on it, but during cold months it must also resist heaving. What is heaving? Well, heaving is generally referred to as the upward movement of an item, and when we refer to heaving with decks we are typically addressing the upward movement that can occur at footings and posts. Now that you understand heaving, the questions why does it occur, and what is pushing it?

FROST! Yes, frost. How could a little frost cause something so heavy to move upward? Although to some it may seem impossible it is said that frost has the ability to exert 50,000 lbs of pressure... per square inch! Now that is some pressure, and your little deck footing is no match for its power...unless properly installed. In order to defeat this problem one must understand how it occurs. In the winter, the ground freezes from the top of the soil downward and water in surrounding soil collects and freezes into "frost lenses". When water freezes and frost lenses are created it expands approximately 9% and if your deck footing is in this area it doesn't stand a chance. So what is a builder or homeowner to do? Install your deck footings away from the frost lenses at a proper depth below the frost line. In Minnesota the frost line is at approximately 42 inches and most recommendations state to complete an install of a deck footing at or below 4 feet. Now, while this recommendation is simple in nature there are still many things that should be taken into account that this post has not touch on such as location (frost levels and depths will vary in even in areas of Minnesota), size of deck posts, number of footings etc. and in order to make sure you install your deck correctly always check with your local building department. I hope these few short posts have brought some light to decking systems, and if you have any questions on decks give us a call today!

Randy King, Progressive Home Services. Greater Mankato, St. Peter, and New Ulm Home Inspections.

Building a Deck? Have a deck on a home your thinking of purchasing? Don't wait any longer! We perform home inspections, deck inspections, roof inspections and much more 7 days a week in greater Mankato, St. Peter and New Ulm. Give us a call today at 507-382-7007 or visit our website to schedule your home inspection now www.progressivehomeinspection.com.