How to Build a Deck
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How to Build a Deck

Does anything represent summer more than an afternoon chilling on the deck? Maybe there’s a BBQ going, and people are enjoying their favorite beverages while a lazy afternoon slips on. As I sit here, hiding from a cold Southern Hemisphere winter, I’m counting down the days to a languid afternoon on the deck.

A deck is essentially an outdoor room. It adds to the living footprint of the building while increasing the value of your home. It may seem like a huge project best fit for the pros, the truth is, you could build one, even if you have no experience. With the right tools and a step-by-step guide on how to build a deck, you’ll be happy to find out that it’s not such a big undertaking after all. If you need some inspiration to get the ideas flowing first, check out these wooden deck ideas.

A quick note: I’m going to show you two things in this post. How you should build a deck, and how I built my deck. Since every project is different, keep in mind that you don’t have to do exactly what I did. Instead, make sure that your deck suits your style. 

Things You Need

Collection of tools on deck
Image credits: Michael Harris

First, gather all the tools and materials you’ll need. As a lot of the materials I used were salvaged, most of them are not standard for decks. But as you’ll soon find out, this isn’t a problem, and my deck performs exactly as it should.

Materials:

  • Posts (mine are round, 5 inches thick)
  • Framing timber. I used 152mm (6 inches) wide joists. The width of your joists is determined by their span, and the span is determined by the size of your deck.
  • Coach screws/lag bolts. You can use either. I used coach screws, half an inch thick and 6 inches long.
  • Washers
  • Joist hangers
  • Decking boards
  • Decking screws
  • Spacers (more on this in Step Seven)
  • Optional: nail-in anchors, ready-mix concrete

Tools:

  • Saw (I used a jig, but whatever you have available should do the job).
  • Drill
  • Drill bits
  • Speed square
  • Sharpie
  • Tape measure
  • Wrench
  • Screwdriver or impact driver
  • Level
  • An extra set of hands
  • Builder’s string

Floating Or Fixed?

Before we even get into the planning phase of your deck, you need to consider how it will be attached to your house. You could build a floating deck, which rests on posts in the ground and is not fastened to the building at all.

You could also attach the deck to the building with something called a ledger board. The choice is yours, and both options are easy enough for the average DIY’er. I built one of each so that I could show you both options.

Step-by-step Guide: How To Build A Deck

Before you get into the step-by-step instructions below, you need to plan your deck out. It might seem like an unnecessary step, but trust me when I say that drawing a plan up will save you time and money. It’s a crucial step in getting the right dimension materials that you’ll need for your deck.

Also, consider the height of the deck. If it’s fixed, do you need it to be flush with the interior floor level? Do you want it one step up from the regular ground level? Remember to include the thickness of the final decking boards in your calculations. These are all things to consider, and this is the time to make those decisions.

It’s also a good idea to accurately mark out the area where your deck will be. Make sure the dimensions are as close as possible and that all the corners are right angles.

Step One: Dig

Red and blue spade in the dirt
Image credits: Manfred Richter via Pixabay

Disclaimer: I managed to skip steps one and two. I attached my deck to the posts that were originally part of a stable. Each situation will be different, so be ready to adapt to whatever comes your way. That’s the fun part about DIY: things rarely go according to plan.

Like any big project, you have to go down before you can go up. Because you planned out your deck so nicely in the step above, you know exactly where the corners of your deck are going to be. And this is where you dig. If you’re building a floating deck, you need a hole in each corner. If you’re building a fixed deck, only the corners furthest from the house.

Your hole should be at least a few feet deep and a foot or two wide. It will become the foundation for your deck, so spend some time digging deep holes. You may need extra support posts along the length of your beams. Ask your timber specialist what the recommended unsupported span is of the thickness joists you choose.

Step Two: Set Your Posts

Round post with bubble level
Image credits: Michael Harris

Once you’re happy with your holes, it’s time to set your posts. I like to drop a big stone, brick, or piece of rubble in the bottom of the hole for my post to sit on. There’s some belief that this prevents termites, but I do it because it distributes the weight of the deck more effectively, lifts the wooden post of the native soil, and makes setting the post easier.

You’ll need an extra set of hands here. Get the post roughly into place while the other person mixes some concrete. I use the ready-mix concrete packs from my local hardware store so that I don’t have to worry about dry material ratios. Just add water.

While one person holds the post roughly vertical, the other person can fill the hole with concrete. Once the hole is full, use the level to make sure that the post is exactly plumb. You will have some wiggle room for a few minutes after you pour the fresh concrete to make minor adjustments to the post.

As long as the posts are high enough, I don’t worry about them being too high. You can easily cut them down to size later on.

Getting these posts plumb is a crucial step, so make sure you’re in the right headspace for finicky minor adjustments as you set your posts.

Repeat for each corner, or only two corners if you’re building a fixed deck.

Pro Tip: Once you add water to concrete, the clock on your working time starts ticking. It’s best to use it within 30 minutes, preferably as soon as possible.

Step Three: Fix Ledger Board (Fixed Deck Only)

Ledger board attached to wall
Image credits: Michael Harris

If you’ve decided to attach one side of the deck to your house, you’re going to need something to attach it to. Here’s where a ledger board comes in. A ledger board should be the same width as your joists. It’s always best to keep all your framing timber the same dimensions.

Your ledger board needs to be at the same level as the other framing. To determine this height, find your finished deck height and subtract the thickness of your decking boards. It is your frame height.

Mark your frame height on the wall of your house. It’s a good idea to mark this in various spots along the wall for precision. The best way to do this is to hold the actual ledger board along the wall where it will be fixed (you’ll probably need an extra set of hands here). Lie a level on top of the ledger. Make minor adjustments until the ledger is level and in the correct position. Make a mark on the wall along the top edge of the ledger.

Next, mark your fixing points on the ledger board. I marked mine every 15 inches. However, the first one was 7 ½ inches from the end of the board. It allows the nail-in anchors to fall in between each joist, which will make your life much easier later on.

Alternate the nail-in anchors between the top and the bottom of the ledger. I was happy with “closer to the top” or “closer to the bottom” as you can see in the photo below.

Now drill your marked holes in the ledger board. Next, hold the board in place, and use the newly drilled holes to mark where on the wall the anchors will go. Since I was fastening my deck to a masonry wall, I used the biggest nail-in masonry anchors I could find. Drill holes in the wall at the marked places. Nail the plastic sleeve into the hole, hold the ledger board in place, and screw the anchors into the sleeves with a washer and the ledger in between. Your nail-in anchors should have their weight rating on the packaging.

You might have to adapt this step depending on what kind of wall your ledger is attaching to.

Step Four: Build The Frame

Deck frame
Image credits: Michael Harris

Now it’s time to build your frame. The height of your deck is up to you. Just remember that the higher your deck is, the more you should over-engineer it, with bigger supporting joists and stronger fasteners.

Mark the frame height on your posts. You could use a laser level here for maximum accuracy. If you don’t have a laser level, some string and a bubble level will do the trick.

Next, place your framing board in place and get that extra set of hands to help you hold it in place and level. I then drilled a hole straight through the frame and into the post in one go. Make sure you keep your drill straight, unlike in the photo below.

Yellow drill drilling a hole
Image credits: Michael Harris

Remember there’ll be two holes in each post. That’s why you have to offset them, so they don’t collide.

Now it’s time for your coach screws. These are oversized screws, extra-long and with a wrench head. They’re designed for jobs like this. I chose screws that were one size smaller than my posts.

Screw the coach screws into the beam and then into the post. It’s a good idea to add a washer here for peace of mind. Never over-tighten coach screws. The extra length means that too much torque will easily snap the screws.

Coach screw and wrench
Image credits: Michael Harris

Repeat this step for each beam. Make sure each beam is flush with the perpendicular one. If you’re using a ledger board for a fixed deck, follow the steps in Step Six for hanging joists to complete your frame.

Make sure that any access to the void underneath the deck is sealed off. You can do this strategically when putting your frame in place.

Pro Tip: When pre-drilling holes, drill the hole size or two smaller than the screw that you’re using. It provides enough ‘bite’ for the threads of the screw to grip into but removes enough wood to give the screw space to penetrate.

Step Five: Measure And Cut Joists

Measuring tape measuring joist
Image credits: Michael Harris

I always wait until the frame is built before cutting the joists to length. It eliminates any discrepancies between theory and practice. Don’t assume that each joist will be the same length or that your frame is completely square. Remember, DIY projects rarely go exactly to plan. Measure the space where each joist is meant to go to be extra sure.

Once you’ve determined the length of your joists, it’s time to start cutting. Since they are so wide, measure the length from either side of them. Make sure the tape measure is as straight as possible and running along the same edge down the joist, like in the photo.

Next, make a mark on both edges of the joist at your desired length. Use the speed square to line your marks up, and make a line. It is where you cut.

Hand using speed square
Image credits: Michael Harris

Pro Tip: Use ‘carrots’ to mark your lengths for added precision and less guesswork (see photo below).

Measuring tape on wooden plank
Image credits: Michael Harris

Step Six: Hang Joists

Deck frame details
Image credits: Michael Harris

Once your frame is in place and level, it’s time to mark out where your joists will sit. You want it every 15 inches in the center. It means you measure from the center of one board to the center of the next. You can see my markings in the photo below.

Mark these locations on both sides of the frame so joists are as close to right angles as possible. If your deck isn’t a square shape, it should span the short side of the rectangle. In other words, you want your joists to be as short as possible for added rigidity.

For fixed decks, this is where the staggered nail-in anchors on your ledger board come into play. Since the anchors and joists should be 15 inches apart, the staggered anchors will offset the different pieces of hardware so that they don’t clash.

To make your life easier, you want to attach the joist hangers to the joists before attaching them to the frame. These hangers nail in easily with joist nails. Make sure the hangers are flush with the edge of the joists, otherwise the hardware will throw all your measurements off.

Slide, lift or force the joists into place. Only fasten the hangers (and therefore the joists) to the frame when they’re perfectly in position. The top of each joist should be flush and square with the frame. An extra set of hands helps.

Remember that it’s unlikely that each joist will be exactly 15 inches apart due to the variable sizes of decks. Use your discretion to make it work.

If you’re building a fixed deck, the beams perpendicular to the wall will be fixed in the same manner.

Deck joist hanger
Image credits: Michael Harris

Step Seven: Lay The Deck

Deck frame with joists in place
Image credits: Michael Harris

Now comes the fun part; laying the deck. Whatever is under your deck probably won’t be seen for a long time, so it’s a great way to ‘get rid’ of your worst material. I live in a rural area, and rubble removal is prohibitively expensive when it’s available at all. So I hid a lot of the rubble from the renovation underneath my deck. I was the only one who knew this, but now I’m revealing my secrets to DIY’ers the world over.

Start on the side of the deck that will be the most seen. Lay a decking board on top of the frame and joists. Make sure it’s flush with the frame on all sides. If your decking boards are longer than your frame, it’s possible to trim the excess wood off later for a flush finish.

Use decking screws to fasten the decking to the joists, two screws per joist. Depending on your wood and screws, you might have to pre-drill every hole. I used softwood and decking screws which did not require pilot holes which saved me a lot of time in drilling.

When laying your decking boards, it’s important to leave a gap in between each board. The reasoning here is that wood warps. It bends and buckles as it dries and is exposed to the elements. If we don’t allow space for this movement, the boards would butt up against each other and crack. Ask your timber specialist what size gap they recommend when you buy the decking boards.

Having many spacers, all the same size, to keep the gap between each board consistent is paramount to a professional-looking deck. You can buy spacers designed specifically for this job, and some can even be pumped up with an air pump for easier removal.

I didn’t have any spacers, and I wasn’t about to go to the hardware store again, so I improvised. I had a lot of broken tiles lying around from the renovation, and they turned out to be close enough to the width I needed between my decking. So I used several broken tiles to evenly space my decking.

If you want to keep your screws all in a straight line for that professional touch, use a speed square to line up the screw locations as you move along.

Don’t underestimate how long this step takes. You’re going to need a lot of screws. A battery-powered impact driver will speed things up significantly.

Two deck boards with spacers in between
Image credits: Michael Harris

Step Eight: Put Drinks On Ice

Completed deck
Image credits: Michael Harris

Sometimes during Step Seven, you’re going to want to put some drinks on ice. You’re closing in on the final moments of your deck build, and the most satisfying part of the whole project is when you’re relaxing in a deck chair on your newly built deck, sipping on something cold. It is an important step and shouldn’t be skipped.

Pro Tip: Unpack the individual drinks from their packs and put them in the cooler box before you drop the ice in. It results in quicker and more even cooling of the drinks.

As you can see from the photo, my floating deck was phase one of a multi-phase project. There’s still a bar counter, a pergola, and an outdoor cooking area that I will build into this area. Oh, and the cottage needs to be finished too. But those are topics for other posts.

Decked Out

There you have it, your deck built with your own two hands. This tutorial intends to show that some of the more intimidating DIY projects are accessible if you put your mind to them. You just need to break them down into small steps, get familiar with the terminology and a few processes, and get on with it.

You can find the building codes for your particular area online. These will be filled with requirements regarding timber dimensions, distances between joists, what grade of hardware is required, and a whole host of other boring stuff.

You can follow this code closely. Or you can use the code as a suggestion and adapt your deck to your situation. After all, it’s your deck, and you make the rules.

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