DIY Outdoor Living Space – Part 2: Foundation and Base Structure



Foundation and Base Structure

In Part 1 we covered the basics of coming up with the design, rough planning materials, and determining space. Now that you have your plan, the real fun begins.

For our outdoor living space we settled on an outdoor kitchen, gas fireplace, two sitting walls, and a pergola. The fireplace top serves as the 4th pergola post and sitting walls link the fireplace to the two adjacent posts. The three posts are then wrapped in decorative stone a little higher than each seat. See Part 1 for the rough drawing.


The first part of preparing the foundation and base structure is understanding what your ultimate structure will look like. For example, the prep for concrete block is different than the prep for buried wood posts. When researching the best ways to do this there were three primary ways that I kept running across:

  • Wood structure, as demonstrated here. This uses a pressure treated wood structure as the base. Stone is then hung on cement board. This is a viable option but you must consider the sturdiness of this approach for what you are building. For our needs this would not have been anywhere near strong enough to support all the weight we will be throwing at it. That, and we live at the business end of Hurricane Alley.
  • Pre-fabricated kits, as found here. These are good options and provide a wide array of styles to choose from. We opted to go with self-built for two main reasons. First, the cost of self building is far cheaper. Second, I like building stuff.
  • Concrete / cinderblock based, as demonstrated here. Given that I like to build things and we want something very sturdy to hold the weight we’ll have on top of it this is the route we opted for.

So concrete blocks it is! Those are heavy – around 28 lbs a piece – and we don’t want them shifting so we’ll need a solid foundation – meaning concrete.

Prepping the Foundation

The first part of prepping the foundation is getting your layout marked. There are a few different ways of doing this. If you know the layout already and have everything marked you can jump straight to digging. In our case we wanted to play around with the final placement and size of everything so we created the forms first.

To create the forms we just cut 2×4’s and 2×6’s to the sizes we needed then screwed them together. Most forms you see will use nails but since we were moving things around and wanted to play with sizes screws were easier. Once the concrete is poured we just cut the forms off with a reciprocating saw.

For the weight of the fireplace portion we need a deeper foundation so that portion uses 2×6 boards for the frame. The rest uses 2×4. The cross beams in these pictures are simply support to maintain shape until the forms are secured in the ground.

Yard with fireplace, sitting walls, and pergola posts laid out.

You’ll notice some posts in the above post as well – this is where we were figuring out the placement of the posts for the pergola. We started with the center post in the fireplace then measured out the distance we wanted for each of the adjacent posts – in our case 15 feet. You can then use some basic math to ensure the placement is right and you have a perfect square.

Fisheye view of yard showing the full layout, including the outdoor kitchen.

Once we had the forms created and final placement we moved straight to digging.

Digging Prerequisites

Before you start digging you need to make sure utilities are all marked. You can do this by calling 811 or by visiting The fines can be very steep if you damage a public utility. The degree of the fine will depend on the extend of damage caused, whether people were injured, etc.

Note that they will not mark utilities between multiple buildings on your property, such as the main house and a detached garage. Likewise, they will not mark irrigation lines. You’ll need to know where these are and avoid them. In the case you do cut your irrigation lines they can easily be repaired using a flexible PVC repair kits. I don’t have any pictures but I accidentally cut through one of the pipes and, while a pain, only took 30 minutes to repair between digging, putting new pipe in, and cleanup. If you cut one of the main utilities between buildings shut them off and seek professional help.

Digging and Forms

Since we already had the forms placed where we wanted them we started digging by digging a line a few inches around the entire form. We then removed the form and dug the entire section out.

It is important to keep your final height in mind and make sure that you are digging to a depth appropriate for that end height. You’ll want to dig slightly deeper than needed to get the form to its final height. In our case, we are re-grading the yard so that it will drain better. Because of this we have some areas that stick out of the ground quite a bit and others that are completely submerged.

Note that you’ll need to either cut or move any irrigation lines. What you do with them is dependent on what your plan calls for.

Once you have your areas excavated drop the forms back into the ground. You’ll then use wood stakes to secure them at the right height. Place the stakes around the perimeter of the form, one at each corner then a few along the edges. Adjust the form to the correct height then either screw or nail the stake to the side of the form. Screws proved easier for us and allowed for us to shift sections of the form height if we needed adjustments.

It is extremely important to make sure you have a level form. Without this anything you place on top of the foundation can shift, causing cracking or other structural issues. To do this simply place a level on the forms at various places on the forms throughout the digging process

Fireplace and sitting wall forms buried, leveled, and secured with stakes.

Kitchen area forms buried, leveled, and secured with stakes.

IMG_0489Forms showing secured pergola posts, rebar, forms, and buried gas line.


Once you have the forms secured you need to add rebar, which will add strength to the concrete and help prevent it from shifting or cracking.

In our case I went to my local big box home store to get the rebar and have a couple lessons learned here.

  • First, rebar is very rusty and can have some sharp edges. Wear some gloves when handling it both to protect from cuts and to keep your hands from being stained a bright orange.
  • Second, I asked one of the people in that area of the store what they recommended to cut it. I was told to get a heavy duty set of bolt cutters. Don’t do this. It doesn’t work. I ended up bending my rebar for the foundation then went and bought a Dremel Sawmax with a metal cutting blade for the rest of the work. This worked great – just make sure you wear eye/face protection as it does kick back some little metal particles.

You’ll want to make sure that you have rebar around the perimeter then woven throughout the middle. Cut pieces to length then tie multiple pieces together with rebar wire. Then place the assembled rebar into the form, using rebar chairs to ensure rebar is at the center height of the form.

For the foundation forms in the pictures above all of the rebar was bent by hand. To do this simply mark out where you are going to need a bend, place your foot about 2 feet down, then pull on the side your original measurement is. A word of caution – this is very tough work and is not the easiest way to do this. The most sore I have ever been in my life is after spending 3 hours bending rebar by hand. You’d be far better off to purchase something like the Sawmax then measure and cut.

Gas and Electric

If you are running any kind of gas or electric underground you’ll need to know the code for your areas and/or seek professional help to get this done. I was having trouble finding definitive codes for these for our are so I chose to go with the most conservative of the national codes and decided to dig 18″ trenches for our needs.

In our case we needed electricity for lighting and gas for the fireplace to be run out from the house and kitchen area to the fireplace and sitting wall area. After marking out the start and stop points we dug the two trenches, making sure they were at least the target depth along the entire length.

IMG_0433-e1449352184859-768x1024Two 18″ deep trenches being dug for electrical and gas lines.

Right after the trenches were dug we experienced a few weeks of historical levels of rainfall. So we were left with hundreds of gallons of water in both trenches and all of our forms filled to the top. The pictures above show them nearly full.

After trying a ton of different methods – from a homemade T-syphon to a drill powered garden hose pump to a barrel syphon rigged to a garden house – I finally settled on a way that really worked well. I ended up buying a Shop Vac with a built in water pump. With this I simply hooked up a standard garden hose, ran that to the street drain, then started sucking the water out. It took about 2 hours to clear entirely but it worked great. I wish I had a picture of me sitting in my lawn chair with a cold drink holding the vacuum hose in the water to share…

Once the trenches were fully dug and dried it was time to drop in electrical conduit. I wasn’t ready at this point to actually run any electrical so I simply fitted pieces of electrical conduit together, using PVC cement, dropped them into the trench, then covered them up. If you go this route be sure to seal each end of the pipe with either a PVC cap or some other means to keep water from filling the pipe.

The final step before concrete was to lay gas lines. I can do most things but gas is such a volatile change that I paid someone to do this part. I’d rather pay and know it is safe than save some money and end up having someone hurt. They came out and dropped a gas line, capped it at both ends, then pressurized it. They left a gauge on top so that we’ll know if anything during construction compromised the line.


At this point your prep is done and you are ready to pour some concrete. Unfortunately I don’t have a lot of good pictures of this part. Both my wife and I were actively pouring and neither of us stopped to take pictures.

We ended up pouring around ninety 80lb bags of concrete (that’s 7,200 lbs BEFORE adding water…). After doing the math on how much we needed to mix for this project it made a lot of sense to purchase our own mixer. We ended up getting one similar to this one and were able to mix two bags at a time.

We got a pretty good rhythm down after a few runs and it went like this:

  • Pour mixed cement into wheelbarrow.
  • Scrape sides of mixer and dump again.
  • Pour 1/2 of water into mixer, add two bags of concrete, then add rest of water.
  • Refill jug with water and rinse concrete dust from skin.
  • Take wheelbarrow to form and dump.
  • Spread and pack concrete in the form, taking care to preserve the placement of forms and rebar.

This cadence took about 5 minutes each, which is about how long each load is supposed to mix. We ran about 45 loads, which took us around 5 hours, including breaks.

The concrete mix will vary depending on the moisture content of the mix, the humidity, the temperature, etc. When you mix make sure you follow the manufacturer’s directions. Adding too much water will weaken the concrete once it dries. For standard concrete you are looking for something that resembles moist, clumpy sand. It should not flow freely but act more like dirt. You can take a handful of it and should be able to form it in your hand and have it roughly retain the shape. Concrete you see flowing like water is either destined to be weak or has superplasticizers mixed into them. We’ll talk more about superplasticizers when we get to the countertops section.

Concrete_mix3Proper consistency for most concrete mixes.

Once you pour each wheelbarrow you’ll need to pack the concrete down into the form with a hoe or shovel then spread it evenly. Once your form is nearly full use a 2×4 to screed the concrete. Take the board and gently shift side to side as you drag from one end to the other. This is easiest with a helper. Search for a video of this if you need – there are a ton out there.

Once the concrete is screeded you’ll take a metal trowel or float and smooth it, working in arcs. There are a ton of videos out there on how to do this so I’ll not rehash it. For a very smooth surface you’ll want to come back and re-smooth after about an hour. In our case nobody will be able to see the foundation and we are only using it to attach blocks to so the look of the surface wasn’t important enough to us to return for a second smoothing.

With all the rain we had been having we took one final step and covered all the slabs with plastic and weighed it down on the sides. This did two things. First, it prevented additional moisture from permeating the concrete while it was still curing. Second, it retained the prescribed amount of water in the mix, resulting in a top strength cured concrete. We left it like this for a little over a week, just to make sure it was fully cured.

Finally, we cleaned up. After 3 showers and some internet searches we found that vinegar will take off the concrete residue. Your skin will still feel a little bit weird but as long as you don’t have hazy concrete on it you are ok. You want to make sure you get all of this off as concrete can cause chemical burns on the skin if left too long.

Next installment we’ll talk about laying concrete blocks.



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Jason McDonald

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