These are just a few of the different types of deck piers. The bottom of the hole should always be in solid soil and below the local frost line. Copyright 2018 Tim Carter

Deck Piers Checklist

• A wide pier base distributes load to more soil
• Reinforcing steel in concrete is a must
• The bottom must be on solid soil and below the local frost line
• Top of pier should be above grade

DEAR TIM: I’m building a deck and discovered that the wooden posts can’t rest on the soil. What I’ve discovered is that I need deck piers. What are they, and how are they made?

Are there different ways to install deck piers and footings? What methods have you used to make sure the piers are installed square and in the exact place so the deck posts are centered on the piers? Jared C., Sacramento, CA

What Deck Piers Do You Use Tim, the Best Ones?

I've tried all types of deck piers and the one I prefer is the one you see me standing next to in the photo just below. CLICK THE PHOTO or CLICK HERE to order these amazing forms. It's the same one you see in the video above - the video I shot at the trade show.

This is me setting a deck pier form at my own home. Yeah, they need to be that deep in the ground in New Hampshire to prevent frost heave. (C) Copyright 2018 Tim Carter

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DEAR JARED: There are very few places you can place a wood deck post on the ground and have it not move. You can get away with that if you place it on bedrock or on some hard-packed material that has a high compressive strength such that the enormous concentrated load on the post doesn’t cause the post to sink into the ground. Solid crushed gravel might give you this condition as would bedrock.

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How Much Does a Deck Weigh?

The average deck can weigh one or two tons. That's thousands of pounds.

These precast deck piers look like giant upside-down golf tees. Once buried in the ground, you’ll only see the top few inches of concrete. PHOTO CREDIT: Tim Carter

I’m constantly amazed at the massive amount of weight the average deck post supports. It can be hundreds and hundreds, and often thousands, of pounds when you calculate the weight of the deck, the furniture on it, and the added weight of people. Imagine the extra weight when a deck is packed with people over for a party or a leisurely afternoon get-together.

How Much Deck Weight Hangs on a House?

If the deck is connected to your house, usually half of the total weight of the deck is transferred to the house’s foundation if the deck is not cantilevered. The other half of the weight might be transferred to the ground on just two or possibly three posts at the far edge of the deck away from the house.

If the posts are just 4x4s, that’s an incredible amount of weight concentrated on an area less than 25 or say 37 square inches!

This is why wooden deck posts must rest on a solid bearing point that won’t sink or lift up because of frost action in a soil that’s in a cold location. You can support wooden deck posts with deck piers in any number of fashions.

Are Concrete Deck Piers Safe?

Concrete deck piers are safe. I’ve used concrete deck piers for many years.

Several architects I used to work with avoided deck piers and chose to employ a deck post footing thinking this would make life easier for me the builder.

What is a Deck Post Footing?

A deck post footing is simply a 20-inch or larger diameter pad of poured concrete down at the bottom of a hole that’s dug in solid soil. The bottom of the hole needs to be below the local frost level.

This is a simple deck post footing. Concrete is placed in a hole and a deck post rests on top of the concrete. Copyright 2018 Tim Carter

Are Deck Post Footings A Good Idea?

A deck post footing is not the best idea.

The wooden deck post is then placed on this concrete pad after the concrete hardens. The only trouble with this method is that the wooden post can be attacked by termites.

I’ve seen treated lumber, rated for below-ground burial, eaten by termites. I’ve come to believe it’s best not to place wood in contact with the soil as I don’t want to hope it will not rot. Hope is the emotion of last resort.

Lookie lookie, Can you see the extensive termite damage on the right side of the post? Imagine my reaction when I pulled this post out of the ground. ©2017 Tim Carter

What is a Concrete Deck Pier?

A concrete deck pier is simply a column of concrete that rises up out of the soil and a wooden post is connected to this concrete column. Usually, the pier is 6 to 8 inches in diameter.

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Can You Buy Precast Concrete Deck Piers?

You can purchase precast concrete deck piers that do a great job of providing support for deck posts. These piers are wider at the bottom than at the top.

The wider bottom helps distribute the weight of the deck on a wider footprint of soil so the pier doesn’t sink into the ground. The piers come in different heights depending upon the frost level in your area and the depth to solid soil.

Are There DIY Concrete Deck Piers?

You can also pour your own DIY concrete deck piers. There are any number of handy plastic or cardboard forms that allow you to create your own professional looking piers. The key is to place them in the exact position making sure the wooden deck posts rest centered on the concrete pier.

I’ve seen carpenters and homeowners go to great lengths to measure and calculate where deck piers should be so they are in the precise location. Time after time I see mistakes made and the wooden deck posts only partially rest on the concrete piers or miss them entirely.

What is the Best Way to Locate a Deck Pier?

I’ve found the best way to ensure the piers are in the right spot is to build the outer frame of the deck and temporarily support it. If you make sure the outer frame of the deck is level and square, bracing it to hold it in square, then you can drop a plumb bob from the deck corners down to the ground. This allows you to place the pier perfectly. It’s that easy.

How Can You Temporarily Support the Deck Frame?

If you decide to construct the outer frame of the deck all you have to do is support the outer floor joists with 2x4s that are set on a small scrap of 2x4 that lies flat on the ground. Be aware that the weight of a single heavy 2x10 treated floor joist can be enough to cause the single 2x4 to sink slightly into spongy topsoil should you not use the scrap block. The scrap of wood will distribute the weight just as the wide bottom of the concrete deck pier.

How Do You Square a Deck?

It’s easy to square the deck frame if you're building a simple square or rectangle deck. All you have to do is make sure the lengths of the parallel sides of the deck are the same. This means that if you’re building a 12 x 16-foot deck that the outer frame has two sides that are exactly 12 feet and the other two are 16 feet.

Once the outer box is nailed together you take a tape measure and see what the diagonal measurements are from corner to corner. The odds are they will be different by several inches.

When you move the outer frame one way or another you’ll quickly discover you can make the measurements the same. When this happens, the outer frame is now square. Nail a long 2x6 diagonally from two of the connecting sides of the outer frame to lock it into this square position. It’s that easy, there’s no need for a fancy calculator or tricky high school geometry.

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This sample piece of redwood decking looks normal, but it’s not. It has a special profile that allows it to resist rot longer. Also this piece of wood decking has almost vertical grain. Note on the edge facing you the dark summer grain wood lines are nearly straight up and down. This wood grain profile is best for decking and ensures you don't have shards of wood peeling up from the deck that is common with flat-grained lumber. PHOTO CREDIT: Tim Carter

DEAR TIM: I'm about to build a new deck and really love the look and feel of real wood. All the composite decking materials try to mimic wood, so there must be a reason for that. I've got my eye on redwood decking and wonder if it's really all it's cracked up to be. Have you ever installed a redwood deck, and what can you tell me about the material? Are there any special considerations or new products that will allow the wood to last longer? What's involved in redwood deck maintenance? Bobbie M., Durango, CO

DEAR BOBBIE: I've worked with redwood for years as a builder and carpenter. I'd be lying if I didn't tell you I'm smitten with it. Not only is redwood gorgeous, it's naturally rot resistant. Granted, it's not as durable as oak or maple when it comes to hardness, but it makes up for this in so many other ways.

I agree with you about the plastics industry. For as long as I've been a builder, the vinyl siding business, the composite decking manufacturers, and even companies that make plastic interior trim moldings have tried to copy the look and feel of natural wood. That alone validates your personal attraction to wood.

It's my feeling that wood is hard coded into our DNA. Our ancestors used it to survive by making shelters, enlisted it to stay warm and dry, and made use of it as a cooking fuel. What I also love about wood, especially redwood, is that it's a crop not much different than wheat, corn or potatoes. The only difference is that the harvest time for redwood and other trees takes place after several years instead of months for most food crops. The bottom line is that we can grow redwood rapidly and continue to enjoy it for generations to come.

I used redwood on the last home I built for my family. It was used for all the siding and virtually all of the exterior trim. I didn't have a deck like you want, but I've installed quite a few redwood decks that still look as good as the day I drove the last stainless steel nail.

I love redwood because it's easy to work with and it has natural chemicals in it that make it rot resistant and not too tasty for most wood-destroying insects. It holds paint very well if you use it for a handrail. When you go to apply your redwood deck finish, you'll discover it readily accepts penetrating stains that will help preserve the natural grain and color of the redwood.

Understand that when you decide to use wood outdoors in just about any other location other than the Atacama Desert, where it often doesn't rain for decades, water is the enemy of wood. Redwood can be damaged by water, it just takes longer than other woods that you expose to water.

It's imperative that water not pond on horizontal deck boards and that water is allowed to drain away from between decking boards as rapidly as possible. The way redwood and many other lumber was milled for years produced boards that had parallel faces on each piece of lumber. While this seemed like a good idea at the time, it turns out that water could take advantage of this profile.

You can now purchase redwood deck boards that have a very unique profile. The top surface of the boards has a slight crown to it like a roadway. This means the center of the board is slightly higher than the edges. Water readily flows off the top surface of the board.

The edges of the new redwood lumber are canted inwards slightly so that when two boards are placed next to one another, the gap at the bottom is wider than the top. This promotes excellent drainage and prevents organic debris from getting trapped between the separate pieces of lumber. Trapped organic debris holds water and accelerates wood rot.

Finally, the lumber mill cuts in two drip channels on the bottom of each board along the entire length. These grooves cause water that rolls under the wood to drip off the lumber instead of soaking in the underside. All of these things help extend the life of the redwood.

When choosing a redwood deck cleaner, I urge you to use oxalic acid or try a mild liquid dish soap and water. Avoid oxygen bleach as it can sometimes darken redwood. If your redwood darkens, you can often rejuvenate it by treating it with oxalic acid.

If you decide to use redwood for your deck, understand that this lumber comes in different grades. Some redwood is clear and free of knots. This is usually the most expensive.

You can get redwood that is less expensive that has tight knots in it. This grade is sometimes called Construction Grade. It will perform as well as clear, but it just lacks that perfect appearance.

Be sure to read all the written installation instructions published by the California Redwood Association before you construct your deck. Pay attention to the type of fasteners you're supposed to use. I would only use stainless steel nails or screws myself.

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