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Part 2: How to Build a Freestanding Deck?

Monday, December 18, 2023

In the previous post, we learned about the preparations for building a freestanding deck. Once these prep work preparations are done, we can start building a freestanding deck. If you have some experience installing outdoor projects, then you can choose to DIY your own deck installation.

Step 1: Plan and Clear the Deck Site

The first thing you need to do is to clear under the deck of unwanted plants and debris. The ground doesn’t have to be level, but it will be easier to work with if it’s relatively close.

Put together a box from long 2×4 wooden strips that are exactly the same size as the outside of the deck. If the deck is square or rectangular, you won’t need to do any calculations to level it. If the two diagonals across the box are the same size, it is a square. Install an 8-foot vertical support at each corner. This will help the box keep its shape and squareness.

Place this box on the ground after the deck is built. Support it and level it with small temporary 2×4 legs, bricks, or anything else. From now on, you will be able to find exactly where the footing holes were drawn by the structural engineer or builder.

You can use spray paint to roughly outline the holes you need to dig for the footer bolts. Remove the box before putting it down and make sure it stays level. You will need to use the box again when pouring the footings, carefully placing the support bolts into the wet concrete.

Step 2: Digging Concrete Foundation Holes

Dig holes of the right size and depth using shovels, picks, rebar, posthole diggers, and other tools according to the plans provided by your structural engineer or builder. Cut the required rebar before mixing the concrete. The proper way to do this is to make the bottom of the hole larger than the top. This helps spread the weight of the deck over more ground and prevents the ground from heaving with frost.

In every place where a base is placed, the top of the concrete should be at least 4 inches above the ground or finished grade. This way, the steel or wood deck support posts will be high enough not to be affected by any puddles or water runoff.


This will also make it easier to spot future pest problems. You may need to make some small molds to make the top of the concrete base look more aesthetically pleasing. You can buy sturdy cardboard tubes and plastic shapes made specifically for deck bases.

Once the pit has been dug to the proper depth and the loose soil at the bottom of the pit has been filled in, you can put the 2×4 box you built back into place on the deck. Use this box to help you locate the foundation template. Remember, you need to know exactly where the center of the deck struts will be. Finally, you must place anchor bolts in the wet concrete at this center point.

Step 3: Pour the Concrete Foundation

This depends on how much concrete you need. You can order it from a ready-mix concrete plant, or you can purchase bagged concrete and mix it yourself. After doing the math, you may find that bagged concrete is the better choice in most cases.

Bagged concrete should have instructions on how much water to add. Simply follow the directions. If you add too much water, the concrete will become soft. After mixing, the concrete should have the consistency of thick applesauce.

Fill the holes with concrete and mix well until there is enough concrete in each hole to fill the form. To smooth the top of the base sticking out of the ground, use wood or magnesium floats. Place a ground bolt right in the center of each post supporting the deck.


Step 4: Install the Posts

Free-standing deck posts are very important. They are the only thing that will hold the weight of the deck to the concrete base. You do not want to see struts that are not sturdy. For this reason, an engineer or builder will likely require 6×6 wood posts.

The ground bolts you install will secure the galvanized hardware strut supports to the concrete footings, which is where the struts will go. With this device, the wood post will be about an inch off the ground. This is a good idea in order to keep the wood post as dry as possible.

Insert the hardware post base into the concrete footing and then erect all the posts. Support them with 2×4 stakes driven into the ground. It is important that each post is straight on both sides. Make sure the posts are slightly longer than needed. Once they are all in place, they can be cut or notched to the proper height for the beams. Make sure the posts are secured in place so they don’t collapse.

There may be two beams on the deck, one on each of the two longest legs. You can use a circular saw and reciprocating saw to make an L-shaped notch for these beams to fit into. If you don’t want to make an L-notch, you can purchase special steel framing connectors to place the crossbeams on top of the posts. Be careful not to simply nail the beams into the posts.

Once you know how high the beams are, you can calculate where the tops of the posts will be placed. An optical or laser level used by builders can help you make sure the tops of all the posts are level. Double-check the numbers three times before you cut off the excess on each post. You only get one chance to get it right.


Step 5: Assemble the Beams

Your beams will be the correct size according to the engineer or builder. For both the beams and the framing, try to purchase #1 grade lumber. This lumber has fewer knots and is therefore stronger. Remember to follow the steps on the architectural drawings to build your beams. In most cases, you will need to nail or bolt two pieces of wood together.

Modern treated wood has a lot of copper added to it to prevent wood rot. When copper comes into contact with water, it can cause iron or steel to rust badly. You must use nails, bolts and other tools that can withstand this level of contact. Also, an engineer or builder can point out the safest screws and bolts.

Step 6: Setting the Crossbeams

Crossbeams can be heavy. If the crossbeam is more than 5 feet off the ground, stand on a platform using pipe supports. Get enough people to help move the crossbeam and hold it in place while securing it to the post. It’s also important to follow the steps on the engineer’s or architect’s drawings. There is no need to guess how to attach the crossbeam to the post. Your life and the lives of your loved ones depend on the deck you’ve built so it doesn’t collapse. Once the beams are in place, make sure it’s level and at the right height.


Step 7: Install the Floor Joists

The size and centering of the floor joists will be written on the plans. It is important to use joists that are flat and straight and do not have a lot of bumps. A flange is a bump on a joist that stays in place. All joists should be crowned in the same manner so that the hump faces up. Any joist with a rough head will need to be cut. You can either draw a line across the tenon and cut it out, or place the tenon of a good joist over the tenon of a bad joist. All joists must be flat or nearly identical at the top if you want the deck to look flat after laying.

Read the instructions before laying any composite decking boards. You may need to lay treated 2×4 boards on top of any joists where the seam at the base of the deck will be. The ends of many types of composite decking need to rest on 1.5 inches of solid wood, not on 3/4 inches of solid wood as they do when butted at the top of a single joist.

Use the proper nails or screws when connecting the joists to the decking. If needed, drill pilot holes so the bottom of the joists won’t split on the crossbeam.


Step 8: Install the Deck Boards

If you are laying composite decking or any other type of non-solid wood decking, be sure to read all the instructions. Composite decking boards require very specific steps to be followed.

When laying traditionally treated wood decking, make sure there is at least ⅛ inch of clearance between each board. In most cases, treated wood shrinks, so you want a ¼-inch gap between boards when laying is complete.

Before laying any decking, apply joist tape to the top of the joists. This tape serves to prevent water from seeping into the joists through the gaps in the bolts that connect the deck boards to the joists. Don’t skip this step, especially if you are laying composite decking boards. This is because composite decking will last at least 25 years. If left untaped, cracks in the wood foundation joists may grow larger over time. This could cause the decking boards to come loose.

When laying standard wood decking boards, make sure the flat grain is facing skyward. If laid incorrectly, water will pool on each deck board. This water will accelerate the decomposition process of the sealer and the wood.

It’s best to secure the boards with screws. The nails will almost always come off after a while. If the deck is near water or the ocean, stainless steel fasteners should be used. Non-stainless steel fasteners will rust faster in salt water.


Step 9: Install Stairs and Railing

Discover the 2×12 lumber needed to make the stringers that will support the stair treads of the new deck. If the calculations are correct, 7.5-inch struts and 10-inch treads will be used to build the steps. The spacing between struts should not exceed 16 inches. For a three-foot wide step, you will need three stringers.

If possible, it is best to place the end of the steps on a concrete pad. If you can bolt a treated cleat to the platform, the steps won’t come off or fall. The stringers are just notched to fit snugly over the shoes.

Railing posts and balusters must meet strict building codes. An engineer or planner will have many plans to meet or exceed this code requirement.


If you have some experience working with woodworking or you like to install your own DIY outdoor projects. Then you can try building your own outdoor deck based on this installation instructions. Of course, you can also hire a professional deck contractor for this project.

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