So, you want to build a ground level deck. First, question: why build a deck? Is a patio perhaps more practical? After all, a patio will last a whole lot longer and require a lot less maintenance. Ah, but a patio involves more labor to install per square foot, especially if you’re starting with a less than optimal site.
Deck or patio? I grappled with this question for, I don’t know, three years before finally making a decision. My solution: why not build both? As part of a significant exterior renovation spanning several hundred square feet, I built both a 180ish square foot free stranding deck and a small flagstone patio. I went with deck for the larger part of the project because I preferred the work and felt more comfortable building something beyond a very basic deck, whereas I don’t think I would have been able to confidently do the same with a patio given the grade challenges at the site. Plus, a “ground-level” freestanding deck is not typically subject to code and doesn’t require footings below frost depth, which avoids one of the biggest challenges with many decks, making this a DIY friendly project.
The previous owner built a very nice hardwood deck off the back of the house. That deck is built on a field stone foundation and varies in height above grade from just a few feet to overhead. It is a rather small and narrow deck, all things considered, about 30’ long but only 4’ wide, so not a lot of usable space.
There is also a very small deck at a lower elevation that served as a platform for a 2-person hot tub, which we removed shortly after buying the house. (Fun side note, if you ever need to remove a hot tub, a reciprocating saw will get the job done).
Just off the “narrow” back deck and “hot tub” deck is our tiny guest cottage and adjacent to that is a bridge across the stream, which I built with the help of a friend using some salvaged I-beams shortly before embarking on this deck project. The task at hand was to tie together all these structures (bridge, cottage, “narrow” deck, and “hot tub” deck) sitting at different elevations in a way that was logical, aesthetic, and inexpensive.
I started this project with a lot of planning. First, I setup some string lines to determine exact elevation differences between the different structures at different points. I knew I was going to need to step down from the “hot tub” deck to the bridge, but I wasn’t entirely sure how many steps would be necessary. I also took some accurate measurements of the area the deck would occupy and then got to work on some design possibilities.
I probably spent at least 10 hours plodding through the design phase. Building a basic square or rectangular freestanding deck on a flat lot with a single step or two would be a very straightforward design. I didn’t think I would need to spend so much time on design but between the elevation changes, the fact that none of the structures were square to each other, and the odd contours of the project area, I ended up drafting about a dozen different designs before ultimately settling on one.
I found these resources to be very helpful with the planning:
Strategies for Safe, Affordable Decks, from the Journal of Light Construction. This article reinforced my assumption that using 2×6 joists was perfectly appropriate for my design. The article includes a link to a deck joist span table, of which there are certainly others available on the Internet, but do be sure you reference one when designing your deck.
How To Build A Floating Deck, from Rogue Engineer. This article was really valuable in guiding some of my early thinking about the design. For example, many of the ground level deck plans that I found while searching around use joist hangers and concrete deck blocks as posts. I can see why this makes sense for a very small, simple build that is going to be plopped onto a flat spot in the backyard, but there are a whole host of reasons why it makes a lot of sense to use a joist over beam design. That sounds way more complicated than it is and Rogue Engineer’s article helped me understand the basics of this type of deck design. My deck build ended up being quite a bit more complicated in the details, but the basic design principles are very similar.
My biggest design challenge was figuring out how to maximize the usable deck space. From my measurements I knew that I had a 15″ elevation change between the existing “hot tub” deck and the bridge. A single 15″ step would violate code and be a generally ill advised way to handle this elevation change, so I needed to plan for two or three steps steps across this span. I ultimately ended up with a design that placed the first step at the transition from the existing “hot tub” deck down to the new deck and then a second step before the bridge, although this step is more of a small landing. There is a final step from the landing on to the bridge. The reasons for this are mainly due to grade and some landscaping that we wanted to keep, as well as some other little nuances that aren’t particularly interesting. All this is to say that there were a lot of details to contend with that were relevant for me but probably would be different for you. Anyway, now on to the broader structural plans, which are relevant to anyone thinking about building a freestanding deck.
Every deck is going to have four main parts: posts, beams, joists and decking. These components work together to make a solid platform. The posts support the beams, the beams support the joists, the joists support the decking. I really liked the idea of using a joist over beam design for the main part of the deck. It is a simple and solid approach to framing. Hanging joists off beams was an option for me and would have saved some time, but – unless the joists need to be in the same plane as the beam – I don’t see a good reason to go this route. In my case, this meant some additional excavation to accommodate the additional depth of a joist over beam on one side of the project. I felt like the extra labor was worth it because – in addition to the stronger structure – there would be more distance between the ground and deck framing and decking, so better airflow under the deck which should extend its useful life.
So, the main deck would have three beams, made from 2x8s laminated together, set on top of 4×4 posts in deck blocks. I would use joist hangers hung off one of those beams to create the step down to the bridge landing. I would take advantage of the existing footing and I-beams of the bridge to support that end of the landing. I confirmed that 2×6 joists were acceptable for my span distances using a joist span chart. Using a 2×6 joists and 2×8 beams in this application is both to code and also saved real money compared to larger dimensional lumber and pricey hardware.
The Build (Part I – Excavation)
I’ve found that any outdoor project invariably involves digging, usually a lot of digging. Even carpentry work. When I built my chicken coop there was digging. Kids’ sandbox? Obviously some digging (and lots of sand shoveling). Building a fence is, in fact, 98% digging contrary to the fact that no one is particularly interested in the part of the fence that rests below ground. Even though I aimed to reduced the amount of digging to the absolute minimum by using deck blocks and deploying a freestanding design, there was a LOT of digging involved before the saws even came out.
Note the copious quantities of field stone over by the wheelbarrow. Ah, New England soil, how I love/hate thee. At least I was able to put all this field stone and dirt to good use in a fieldstone wall.
The Build (Part II – Framing)
I used deck blocks to set the posts. This is much easier than pouring a footing below frost depth, which is 40″ in my area. I did excavate little holes for each of the deck blocks for two reasons. First, they add some height to the posts. The height of the bottom of my beams is indicated by the string lines in the pics below, so I needed to recess the deck blocks in some cases to have enough room for the post and beams. I also wanted to be able to create a solid base for the blocks to rest on, so digging out a hole, then tamping the soil, backfilling with gravel, and then tamping down the gravel creates a much more solid base than simply setting the blocks on dirt. I wasn’t too worried about keeping the elevation of the deck blocks level with each other since I could use the string line to mark the height at which I would cut each post so that the beam would be level. The reason some of the blocks are set much deeper than others is because I needed to dig a little deeper to get to solid ground.
With my deck blocks set, I double checked my string lines to make sure they were all level and then measured the distance between the deck block and the string line to determine the length I needed to cut the 4×4 posts.
At some point between setting the deck blocks and finishing most of the framing I must have just decided to put my head down and crank through the framing (or I accidentally deleted a bunch of pictures) because I’m lacking any documentation between the previous picture and this next one. Probably the former since so much of the prep work getting to this put was either very laborious (excavation!) or very fiddly (setting string lines, getting the deck blocks positioned correctly, etc). But this image, which is of the beam closest to the bridge, offers a lot of useful insights.
First, the beams are laminated pressure treated 2x10s. I applied glue and then fastened these together with structural screws to make a solid beam. One of the downsides to making a beam this way is the potential for moisture to find its way into the small gap where the boards meet. I used a butyl roofing tape to help ensure water sheds off the beam. This stuff is quite pricey at $50+ a roll, but totally worth it in the interest of longevity of the framing.
Second, the beams can cantilever over the posts. I used beam span chart to determine a safe cantilever distance. Being able to cantilever the beam solved a big conundrum for me since I wanted the decking flush against the side of the cottage, but wasn’t sure how to get a post right up next to the field stone foundation. The cantilevered beam allowed me to do this. The decking floats right next to the cottage without adding a load to it or disturbing the field stone foundation.
Third, I used Simpson Strong Tie post caps to secure the post to the beam. Not pictured here, but I also used hurricane ties to secure the joists to the beam.
Fourth, in this photo I had just finished cutting the joist ends flush to the beam. I used a circular saw and then finished the final part of the cut with a reciprocating saw. A rim joist could then be added to stabilize the joists. This would later become a step, too.
Finally, you can see in the image that I added landscaping fabric and a thin layer of gravel below the deck. This prevents weeds from developing and promotes good drainage.
Framing out the joists was pretty straightforward. I just made sure to watch my spacing and check for square before securing them to the beam with hurricane ties. Toe nailing them to the beam is also fine although I didn’t want to penetrate my waterproof beam cover. (I also used joist tape to similarly protect the joists before laying my decking.)
There were a few spots that had some framing complications, in particular in a little corner where the deck, cottage, and patio meet. The deck is neither in the shape of a square nor is it square to the cottage, plus I had a small water featured planned, some steps, and a transition to the fieldstone patio to contend with and a number of tricky problems to solve here.
This is what the framing looks like underneath. There are the “main” joists which are spaced consistently with the rest of the deck framing, but then two additional joists were added parallel to the cottage. This is kind of funky, but I needed the framing to be extra sturdy here because of both the step up from the patio to the deck and from the deck on the porch in front of the cottage door, and there is also the weight of the water garden/rain catchment feature that was my solution for how to manage stormwater runoff from the cottage roof.
The joist framing is mainly supported by the beams, but I did wedge a concrete block under one of the joists for some additional support.
The cottage doesn’t have a conventional gutter. There is some inverted drip edge that channels rain runoff towards a corner where a rain chain helps the water find its way to the ground. At least that is what was in place before the deck. Since putting this “gutter” system a few years ago I had always been bothered by the fact that rain chain basically just terminated into the ground, which was neither aesthetically interesting nor particularly good for the longevity of the field stone foundation of the cottage. Getting that water away from the foundation was something I had been wanting to do, but had never quite gotten around to. But with the deck now square in the landing zone of the runoff, I needed a proper solution. I decided to build a small water feature that would capture the runoff with a hidden overflow pipe that would move the water away from the cottage and deposit it into the stream.
I framed this out with a combination of 4×4 and 2×4 posts. In some cases I was able to set the post on a beam but in others I notched it so that it would hug the joist, which created a very sturdy foundation for the water garden box.
Then I added some additional framing which would serve as both a nailer for a pond liner to hold the runoff water and also the top trim of the water feature. One thing that might this a bit trickier than it needed to be was my decking wasn’t quite long enough to go all the way under the rain garden. Ordering a few boards of a longer length than the rest would have solved that problem, but I failed to account for this detail when planning and purchasing, so I had to cobble together the necessary support from scrap. It didn’t need to be pretty, since it wouldn’t be visible, but it did need be solid. Water is heavy!
Before installing the trim and pond liner, I snaked some black 1/2″ tubing up under the deck and through a little crack. This is the overflow and it works quite well even during intense rain events.
I used a pvc pond liner to make the water catchment. I secured it to the framing with roofing nails. It’s hard to make out, but the overflow pipe pokes through a small slit in the pond liner in the upper right hand corner of this picture. It has been a year and this system is still water tight and works great!
Aside from the trim on the water garden, the next part of the project was the landing by the bridge. For a variety of reasons, most of which I can’t remember now, I decided that a small landing was preferable to a simple step. I won’t go into all the details of what was involved, but the framing was a bit complicated. Since the cottage wasn’t square with the deck, and the bridge wasn’t square with either, and a garden bed that we wanted to retain was also a factor, there were some odd angles to contend with.
I was able to use joist hangers hung off a beam to form part of the framing for the “tread” of the landing. I’m not sure if that is the correct term in this context, but the rim joist on the main deck is the riser, if that makes sense, so you step down 5.5″ (the height of a 2×6 joist) onto the landing from the main deck onto the landing. The other end of the landing is supported by iron I-Beams that are the structural supports for the bridge over our stream. At some point, I’ll do a post about that project, but they proved to be pretty convenient here as a support for this part of the deck. It probably isn’t apparent from the photo, but I created something of an upside down T as a method for fastening the joists for the landing to the I-Beams. I had to rip the top of the upside down T to the correct height and then fastened the bottom part of the T to the I-Beams using metal screws. The joist ends were then fastened to the upside down T and a bunch of blocking was added to support the decking.
I needed to add one post where three different framing members meet (only two visible in the pic below at this point in the assembly). This was a fun little puzzle to solve. I ended up beefing up the 4×4 post by tacking on some 2x4s in addition to notching the 4×4. I’m not sure how others would approach this situation, but this worked fine for me.
The Build (Part III – The Decking and Finishing Touches)
Other than framing out two steps on the side of the deck, this wrapped up the framing and I was ready to lay down the decking. Before I did that I stubbed out the posts for two benches. I looked at a bunch of different plans for building deck benches and many were bigger and bulkier than I wanted, given the relatively small scale of my deck. So I just improvised something that made sense to me. I’ll cover that in more detail later, but I needed to get the posts in before putting down the deck framing. The pic below shows both the start of the decking and also one of the bench posts. I used long structural screws to go through the post and into a joist, and then added blocking to either side of the post to eliminate any wiggle.
I picture framed the deck, which was both an aesthetic bonus as well as an easy way to address the problem of needing to rip some of the decking down to fit the dimensions of the deck. I was using 5/4 x 6″ pressure treated deck boards so I took my total deck width and divided that by the 5.5″ + 1/8″ spacing of each deck board to figure out how many full boards I would use to cover the deck and then used the remainder plus whatever overhand I would want on the last board before the step to determine how much to rip off the first board. I don’t recall exactly what it was, but it was close to half the width of a deck board, which is what I was using for the picture frame, so it looked pretty natural. The only lesson here is to think this sort of detail through before you start laying down decking so you don’t end up with some totally random width board at the edge of your deck. Another strategy is to just take a few fractions of an inch of the last several boards so that the human eye doesn’t notice any meaningful change in the size of the boards.
You do need some extra framing if you’re picture framing a deck. Adding blocking between joists is one way to do it. Since I was going with half width deck boards for my picture frame, I was able to just double up the joists at this one spot where I needed some extra framing. It isn’t visible in the photo, but the board closest to the grass is resting on the edge of a 2×6. I later added a 1×6 fascia board as well do the ~2.75″ deck board has 2.25″ of support underneath it with a 1/2″ overhang.
After ripping down all of the picture frame decking, I decided to use a router to round over the cut edges to give the boards a finished look.
Next I laid down the decking, which is not very interesting work but it goes fast. I used the Camo deck fastener system, which makes things really simple. There are different models depending on the type of decking you’re using. With the decking down on the main deck, I turned my attention to a little porch area in front of the cottage. As mentioned previously, the cottage was not built square to the house, so it wasn’t square to the deck. I also needed to account for a small step up to the porch and then from the porch into the cottage. I also previously mentioned that the length of the decking I bought was just a hair shorter than ideal for the widest part of the deck. I knew this going in, but I also knew I could cut down on a lot of waste by going with the shorter decking and some creativity, but all these factors made this little spot a bit complicated.
Framing out the porch was otherwise pretty straightforward and I had this section completed in short order. Then I turned my attention to finishing the benches, which were at this point just posts poking through the framing.
Framing the benches was pretty fun. I started by cutting the top of the post in half to a depth of half the width of a 2×6 and then I cut a notch into a section of 2×6 so that it could nest onto the post as pictured. The other half of the post top was notched to accommodate a 2×4 that would span the length of the bench.
The 2×4 was notched in the middle to support another 2×6 section. The 2x6s were sized to support three deck boards with 1/8″ spacing between and some overhang.
These benches are super solid and were pretty easy to build. At this point, the only thing left to do was build a set of box stairs off the side of the deck (which I don’t seem to have any pictures of) and then stain the deck.
There are plenty of details that I left out, although perhaps I went into too much depth as is. I’ve always wanted to build a deck, and now I have. It was a lot of fun. I don’t know how long I actually spent actively building the deck, but it took me most of the month of September working 3-4 hours a day, a few days each week.