Your home’s foundation is the most important part of your home. After all, you can’t do much without a foundation. You’ve got to get this right so that the rest of your home will be secure and stable.
For our home addition we built a monolithic stem wall and footing foundation. Meaning the footing and stem wall were poured all at the same time. This type of foundation uses a lot of steel making it very sturdy and strong, and since it’s poured in one shot, it’s a time and money saver as well.
Although my husband is a professional (retired) carpenter, you should hire your own professional. This is a big project and the basis for the rest of your home build. In this post we’ll show you how we built our foundation.
Tools we used:
- pole driver
- concrete drill
- tape measure
- rebar bender
- skill saw
- carpenter bags (to hold tools to our belt)
- Tie wire twister
Materials we used:
- monolithic pouring straps
- plywood sheets
- air vent boxes
- Simpson Strong-Tie strap-tie holdowns
With our materials and tools laid out, we’re ready to start work on the foundation.
Step 1 – Establish perimeter
Before the forms could be built, we first needed to establish the perimeter with string lines and batter boards according to our approved drawings. The perimeter needs to be square and level.
The batter boards are simply strips of wood attached at a right angle and secured with vertical steel or wood stakes. Batter boards will help ensure that the layout of our foundation is level and square. We drove the batter boards in at each corner of the perimeter. The tops of the batter boards are now our guide for the tops of the footer.
Checking for square
To establish square, we attached string to the tops of the batter boards and ran string lines to all 4 corners of our layout.
You can check that your layout is square by using the tape measure diagonally from one batter board corner to another making an X. Then you can tell if you need to make any adjustments to your string on one corner or another until your layout is completely square. I recommend watching a video on how to use batter boards and strings so you can see more clearly how its done.
Step 2 – Build the forms
We ran boards in line with the strings to create the outside perimeter of the forms. Once that was established, we then set the inside perimeter using a cheap block, a level, and the monolithic pouring strap and stakes. Then we drove steel (or wood) stakes in roughly every 2 feet to keep the forms in place. We put a new string line from corner to corner to level and straighten the inside of the forms. This will help remove any sagging and bowing of the forms.
Step 3 – Attach ‘monolithic pouring straps’
The monolithic pouring straps (pictured below) were supplied by our materials provider who carried the foundation metal. Our materials provider informed us that different companies have different part numbers but monolithic pouring straps is the correct name to look for. They generally come in boxes of 50 and range in lengths from 15″ to 27″.
We attached monolithic pouring straps (see above) to the top of footing forms as spreaders. These help stabilize the forms during the concrete pour. Special note: it’s highly recommended to put your steel rebar in the trench before laying down all of the mono pour straps. (See next step). This will allow you to tie your steel together on any flat surface, but most people tie it together in the hole.
Step 4 – Rebar
We installed 3 lines of rebar along the base of our forms. Then we attached short rebar perpendicular to the long rebar and tied with wire in 3 places using tie wire and twister. My husband likes things perfect and made a ‘cheat block’. He took a 1×6, cut 3 saddles into it, and moved it along the rebar to keep the spacing perfect. Now it’s time to install the rest of the monolithic pouring straps. Making sure to put 2 every 8 foot, because it takes 2 cleats for plywood seams.
Step 5 – Adding the ‘cleats’
We also used 8 inch spreader cleats (see mockup below). These sit atop the monolithic pouring straps and can be either taped in place or loosely wired in place. (The appropriate spreader cleat will be called out on your blueprints.) The cleats are designed for different types of plywood, in our case we used 3/4 inch plywood. Our stem wall is designed to be 2 feet tall so we took 4×8 sheets of plywood and ripped them in half creating a 2 foot by 8 foot by 3/4 inch plywood form for our stem wall.
Step 6 – The Stem Wall
We had a boulder in our foundations’ perimeter, and called it the ‘Flintstone couch’. (And funny enough, it actually sits below where our couch is.) So we had to treat it like we did the existing foundation and drill 3 holes to insert rebar lines and used epoxy glue to secure. We could have blasted it, or had it dug out with a big excavator, or jack hammered parts of it away. But all these would have costed extra money and experts and their equipment. A simple phone call and a quick inspection allowed us to drill it and use it. We’re kind of attached to it now. 🙂
Now that all the rebar is complete in the footing, it’s time for us to put the outer stem wall form together. We used 3/4 inch plywood. We started our layout from a specific corner. (My husband calls it ‘indexing’. He’s so OCD, he used the same corner to index the entire house all the way from the foundation to the roof layout.) When you get started on your foundation you need to pick a corner where you always layout from.
The L-Shaped Vertical dowels you see in the picture above we bent ourselves. (You would create vertical dowels according to your blueprints). We installed the plywood sheets around the perimeter creating the stem wall.
Step 7 – Install air vent boxes
We installed air vent boxes on the outer plywood form of the stem wall. These are needed to vent the crawlspace. Once the concrete is poured, the plywood will be removed revealing the air vent boxes within the concrete. This will be our crawl space.
Step 8 – More rebar and strong ties
Somehow we missed taking a picture of an important step we did in our stem wall. But these drawings from our blueprints illustrate it. We bent our own L-Shaped Vertical dowels and placed them every 3 feet along the footing rebar and wire tied them. Next we installed the horizontal rebar for the stem wall using the wire ties and twister tool to attach them to the vertical dowels. (Vertical dowels are really just short lengths of bent rebar).
This is also the step where we placed in the Simpson Strong Ties.
Step 9 – Inner plywood/form for Stem Wall
We’re almost done! We built the inner stem wall with plywood sheets. This picture shows where we put the Simpson Strong Ties we did in the previous step. The orange paint you see shows where my OCD husband marked out where all the beams will go. Most beams will require a beam pocket. A beam pocket is a void in the inner side of the concrete where a much larger beam than the joists would go, or a crossing beam underneath the joists would go. There are several ways to create a beam pocket. You can buy plastic forms to nail to your inner plywood, or you can cut solid blocks to your inner plywood. A beam pocket is generally engineered and called out in the plans for its proper depth and penetration to the stem wall. (Generally half way).
In the above picture, the white boxes inside of the foundations’ perimeter are for footings.
And lastly we braced the forms with 2x4s or 2x6s to provide further straightening and strengthening to the forms.
Step 10 – Pour cement
Right before you pour the cement don’t forget to put the releasing agent on the forms using a bug sprayer. In the old days the release agent was diesel. Today it’s an environmentally safe, biodegradable product.
We poured cement in one shot (mono pour) for the stem wall and footer. Directly after filling and leveling the forms with cement, we inserted the anchor bolts. We put them every 6 feet, and 1 foot from every joint of the mud sill.
In the above picture, the white circles within the foundations’ perimeter are concrete footings which are also known as pier blocks.
Step 11 – Strip forms
Later that day we stripped all of the wood forms leaving just the concrete. Now with the wood all stripped, you can see the foundation and crawlspace.
Remember the orange paint and those beam pockets we talked about? That’s where my husband placed the beams.
This is how we built our stem wall foundation. It was a lot of work but we did it! There are important steps to take to ensure your foundations is stable and strong.
Make sure to establish your perimeter first, build your forms and place the rebar within the forms, and pour cement.
If you plan on building your own foundation you’ll need to get blueprints drawn and check code and get inspections in your area. And bring in the professionals. If this is a remodel you will need to join your new foundation to the existing foundation.
I hope this is helpful to you on your home foundation project.
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