Monday, July 14, 2014

From Dirt to Deck - How to Build a Ground-Level Deck

Ever since we moved in, there has been a spot outside the house that has been absolutely useless and bothersome. Heading out the back door, past the newly installed pantry shelves, you step down about 8 inches onto a dirt patch full of weeds. It's lower than the land around it, as if begging for a deck or patio, but we just haven't had the time or money to focus on such a project. It was so boring, I never thought to take a photo of that section of the house. But with the project list dwindling, and the budget opening up a little, we decided it was time to finally take that plunge.

I recently helped Becky's dad, Paul, and her brother-in-law rehab a deck on her sister's house, so I understood the basic idea of how the posts and joists worked, but still needed some assistance in building from scratch, so Paul agreed to help.

I started with a whole lot of planning.

Two of the sides would be on exterior walls of the house, adjacent to the laundry room and the band garage on one side, and the living room on the other. Novice as I was, I made a couple mistakes in these drawings.

One, I assumed that we would need posts along all sides, when in fact you only need them in the opposite direction of the joists. Two, I also assumed that the double 2x6's we'd be using on the front and back (where you see "DOUBLE") would be attached to the side of the posts, but we used a bracket to place them on top. Three, I planned for 5 posts per side, and we really just needed four. Four, we were able to get 16' deck boards, so the 12' spacing you see above is not accurate. So, these drawings helped me visualize, but they are by no means to be used as plans.

Here's the real rundown:

Materials List:
(4) 4x4x8 Treated Posts
(25) 2x6x16 Treated Joists
(48) 16' Standard Deck Boards
(8) Joist Brackets (the ones that slide on top of the 4x4 and hold (2) 2x6 beams)
(19) Joist Brackets (U-shaped that nail to the side of the cross beams and hold the joists)
Post Hole Digger
Bracket Nails
(2) 5lb boxes of Outdoor 2-1/2" Decking Screws

About $1,000 for a 15'x24' Deck


Using a post hole digger, we dug four holes along the house for our 4x4 posts, spacing them 8' apart on center.

Each hole, we were able to get about 3' down, where we actually hit the gravel base of the foundation, and the buried wooden plate. Having that made it really easy to get them straight. We then took our 8' posts and cut them in half using a 10" compound miter saw and dropped them in the holes.

Once we had them all in and up against the buried foundation plate of the house, we poured a half a bag of dry Quikcrete into each hole. You don't need to mix the Quikcrete - the ground water will set them for you. Next, I dug out around the front and side of each post, just a few inches, to get a pencil and reciprocating saw to ground level.

Then we built the first double 2x6 beam. Because the deck is so wide (24 feet), we had to create the double beam using (3) 2x6x16 joists. We cut one of them into two 8' pieces (16 + 8 = 24), and then assembled it so that the seam was staggered when screwing them together, creating a 4x6 that was 24 feet long.

We set the beam on the ground up against the posts, made sure it was level, and marked each post with a pencil. We then took a reciprocating saw and chopped each post in place. That's the quickest way to do the ones closest to the house. If you mark them, then take them out to cut them, you'll most certainly have to make little adjustments with dropping dirt back in or taking it back out, or pounding with a sledge to get them down a little. Neither method is perfect, since using the reciprocating saw is touchy if you don't get your cut exactly level. We had to shim a couple of the brackets for that reason.

We put on the brackets on the posts, and dropped the header in place, making sure the end of the header was about 1" off the wall of the house.

For the posts on the other side, we used the 3-4-5 rule. We used the in-place header and laid a 2x6 on its side on the ground perpendicular to that. We measured 3 inches on one 2x6, made a mark, 4 inches on the other, made a mark, and then measured diagonally across to each mark. Using the Pythagorean Theorem, the measurement across should be 5 inches, and that would make the corner exactly 90°. We marked that with the post hole digger, did the same thing on the other end, and then used those posts to make sure the two in the center were lined up.

You want the deck to slope away from the house, so we cut these 1" lower than the posts next to the house. Again, we used a 2x6 lined up on either side, used a level to make sure it was sloping away, then made our marks. We then used those marks to make the marks on the two posts in the center.

We pulled these out of the hole and cut them on the miter saw, and then made adjustments by adding or removing dirt to get them all level, and then adding the Quikcrete. It was easier to do that since there was no wall to brace the post against as the reciprocating saw moved through the post. Neither option is perfect, but it worked well enough in both instances.

With the other posts in place, we built another header and nailed it in place with the brackets.

Now that we had all the posts and both headers in place and solid, it was time to hang the joists. Because the exterior wall is actually about 15.5 feet, I rounded down to make the dimensions actually 15 feet, which required cutting all the 16 foot joists down to fit between the posts.

We measured between the headers, and luckily it was the same all the way down. We then set up the 2x6 joists on some cinder blocks and got out the circular saw. My saw will only go through one at a time, so we couldn't stack them, but instead, we put two side-by-side, so that as I made it through the current cut, I'd be marking the next board with the saw. That made it so we didn't have to measure each one. We did stop every third or fourth just to make sure we weren't getting to long or short, and made adjustments accordingly.

Now, the worst part about deck building is installing joist hangers. Seriously, it's no fun. Especially with an on-ground deck. We decided because we have such a huge span that the joists are running, with no posts in the middle, that we'd do a 16" spacing instead of the typical 24" spacing, just to be sure it was solid when all screwed together, with no bounciness that you sometimes feel in older decks. We marked both headers with 16" spacing and started nailing in our first joist hanger.

Because the ground was not exactly level, we did have to dig small trenches on most of the joists to get them to seat properly. It was a long, exhausting job, but when it was done, it was a huge relief, and it meant the end was in sight. NOTE: In hindsight, we should have done double joists 8' from each end, so that when I screwed the deck boards down, I didn't have to get so close to the end of each board. They tend to split and crack, and over time that seam might break and I'll have loose boards. I would recommend you do double joists wherever you're planning your deck board seams.

When we moved the joists from the lumberyard to the house, we did it in an 8' trailer with a gate that stuck them on a diagonal into the air, creating a very nasty bounce and potential fishtailing as we drove. It was terrifying, and I couldn't imagine moving all the deck boards in the same manner. So we did a little creative thinking, and realized that my Paul's boat trailer is 17' long, so I sent him fishing as I went off to pick up all the decking.

We took an interior 2x6 board Paul had laying around, cut it into a couple pieces, and strapped them to the front and back of the trailer about 14' apart to use as a base.

The guys that helped me load it were a little surprised, but I'm sure it's not the first time they'd seen something so ridiculous. It worked perfectly, and I got the boards home without worry or incident.

It's worth noting that a 16' deck board is actually a couple inches longer, so if you have to cut the boards to meet a joist, cutting them in half won't work. Because the deck is 24' wide, we had to cut 1/3 of the boards into 8' sections. But when you start at a wall, and have an overhang like we do, you can always allow the boards to go long on the end and then cut with a circular saw once they're all in place.  So we measured one board to 8' and used the same cut-into-the-next-board as we did with the 2x6's.  With each cut, we kept them separate, so there was a "short pile" of boards that were exactly 8' and "long pile" that was the remainder of each, usually about 98" inches or so.  With half of the remaining 16' boards, we had to trim that last little bit off the end so it would meet the joist, so we quickly did that as well.

We then laid out all but a couple rows on the deck surface so we could just pull the next row in while we were screwing it all down, and so the trimmed and long pieces were all in place and we didn't have to worry about pulling from the wrong pile. We also started on the outside, so that if we had to cut boards lengthwise in the end, that short board would be up against the house and not on the outside.

When laying the boards out, we made sure that the curve of rings was always pointed down, so that water did not collect but rather roll down. I'm not sure how big a difference it makes, but it should prolong the life of the wood.

The first row is a trimmed 16' board and a 98" board (the remainder of cutting 8' off a board), and the next is an actual 8' board and an untrimmed 16' board, and then repeat that pattern. This way, the seam alternates sides, and you don't just end up with a line all the way up the deck.

We also wanted to make sure we had spacing in between each board, so that water could drain through, so we used thick framing nails, tapping them temporarily on every other joist and then pulling the next row of boards into place.

The whole project took nearly 1,800 screws - that's the problem with spacing the joists a little closer. At 2 screws per joist, each row took 38 screws, and with 47 rows and no fancy auto-loading screwgun, this stage is no joke.

With standard decking, you'll get some boards that are warped like the one you see below. The way to fix this is to line up the center of the board and screw that down on at least the center joist, if not also the joist left or right of center, and then you should be able to use your foot to kick and bend the ends into place. On some that were more extreme, we had to use a crowbar - I'd stand on a loose board and have Paul crank on the warped board to get it to get as close to the nail as possible.

Just as you would "measure twice, cut once", you should also always check your math, and when in doubt buy more than you need. Otherwise, you'll be on a roll, and end up two rows short and have to drive back to the lumber yard, like I did.

To save myself from having to haul 16' boards again, I bought (3) 8' boards and (2) 12' boards to finish it off. That way, the seam would remain split (using the 12' boards first), and I could just strap them to the top of the car instead of getting the trailer involved.

Once I got the last row in place, I snapped a chalk line along the uneven side and ran my circular saw all the way down. Luckily, I'd trimmed the last two rows before screwing them down, so I didn't have to worry about getting all the way to the wall, but a reciprocating saw would have finished it off no problem.

FINALLY, it was done. After four long days, a ton of screws and a handful of beers, we got it done, and it's fabulous. Now instead of stepping down into a dirt patch, we can walk right out the back door onto a nice clean deck. Unfortunately it means I have to now powerwash that wall. Sheesh.


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