Planning DIY pier and beam foundation
Your first steps for starting a DIY pier and beam foundation are going to be surveying and planning. The first step is to find where on your land you want to build the structure. Mark out where you want the perimeter of the building to be. Make sure the edge of the building isn’t too close to trees, bodies of water, streets and other unstable and unbuildable areas.
Get Utilities Survey
Once you have a rough perimeter marked you need to call 811 to have them do a dig survey. This will make sure the area you are drilling doesn’t have any utilities lines or pipes under the soil. DO NOT skip this step it can be fatally dangerous to dig into dirt where you don’t know what is underneath.
Post the Corners
Measure these dimensions with a long surveying tape ruler. Mark the boundary with orange spray paint (I used gray paint) and wood posts in the ground. Make sure the dimensions of the building are square and running parallel with each other. One way to do this is to make sure your length and width measurements are the same on both sides.
Mark the Perimeter
Once you make the measurements for width and length, mark them with a post. Use orange spray paint to mark the perimeter on the ground of the length and width. You can do this by running string line between the posts in the ground to mark where you should paint a line. Finally make another measurement from corner to corner to make sure everything is completely square. Double and triple check your work.
How many piers per square foot should I have?
| Square feet of house | 100 | 200 | 300 | 400 |
| Number of piers | 6 | 10 | 16 | 20 |
You will want to have piers at least for every 20 square feet of the house. Now you should have a clear out marking of the perimeter of the structure you want to build. The next step is to lay out where the piers will placed within the perimeter you have marked.
How to lay out piers in a DIY pier and beam foundation
The layout you use will depend on the shape of the structure you are building. For a simple square shape make sure the total square footage has a square root that is a whole number. This is because you can’t have a fraction of a pier. For simplicity sake let’s consider a 500 SqFt structure will have 25 piers. Place them equidistant from each other in 5×5 pier rows. The outermost piers should be within 1.5 ft of the marked perimeter.
Non Square
For non square shapes you can use the square root trick again by making sure the total square footage is an integer that is a whole number. For a 600 SqFt house could be 5 pier deep 6 pier tall set up for 30 piers.
Cardboard Marker
You want to start marking where the piers will be going. Since this is based on 12” wide piers you should get a circular piece of cardboard that is 12″ wide. You can spray paint over this cardboard marker onto the ground to show where the pier will be drilled.
Mark the Ground
Start marking a row of piers running lengthwise on the edge of the marked perimeter. Mark the piers position 1.5 ft from the perimeter marking. Once you have one row marked use a string line to make sure it runs directly through the center of every marked pier.
Adding Rows
Run a string line the other way house widthwise. Make sure the the marked row is straight all the way to the other side of the marked perimeter. The string line is should run completely parallel with the width marked lines of the perimeter. You can use the 12” spray paint stencil to mark the ground along these string lines. This will line up the remaining measurements.
Double Check Your Measurements
Make sure everything is square and all of the string lines run through each pier directly in the center. It is immensely important you get these initial measurements right because if you don’t it could jeopardize the project. If you make the right measurements of the DIY pier and beam foundation will be easy to build from here. Triple check everything with string lines.
Markings Complete
You should now have a grid of string lines and circular spray markings on the ground. The pier markings should be spread equidistant in straight rows. If everything is marked correctly you are ready to rent an auger to drill the holes.
How to auger holes for DIY pier and beam foundation?
Make sure to rent an auger that is attached to a rolling platform. Hand held only augers without a platform to hold it are very dangerous and can cause serious injury. If the auger isn’t attached to anything it is free to swing around when being powered causing an injury. You will see at any tool rental store they will have an auger that is attached to wheels.
How deep should a pier and beam foundation be?
The piers of the foundation should be at least 4 feet deep or until you hit bedrock.
Renting the Auger
Make sure you get an auger drill that is 12” in diameter and drills at least 4 feet down. The auger should come with enough gas to drill at least 10 piers. Make sure to figure out what gas is needed prior to leaving the equipment rental store so you are prepared if it runs put.
Getting Started
When you get home with the auger don’t forget to put on a dust mask and goggles before auguring. Pull the drill bit over the circular spray paint markings that you have made. Switch the drill on and let it accelerate to full speed. Push the spinning drill bit into the earth and watch as it easily cuts into the earth. Apply pressure to the top of the auger if there are any tough spots. Drill as far deep as the auger will go.
Double Check Everything
Once the auger has drilled the holes in a row of pier holes, double check your work. Use string line to make sure it runs through the center of each pier hole. You want the piers to be in a straight line so posts can be laid straightly later. Continue drilling the holes until all of the pier holes are complete. You should now have a grid of holes in the dirt that line up with each other lengthwise and widthwise.
How do I pour concrete into form tubes for DIY pier and beam foundation?
Getting Supplies
Head to your local big box store and pick up enough 12” concrete form tubes for the holes you have drilled. These are cardboard tubes that hold your concrete into a pier shape while the concrete is setting. Pick up enough rebar for 3, four foot long pieces in each hole or 3 pieces for however deep your pier hole is.
Do pier footings need rebar?
Yes pier footings need rebar especially if they will be holding weight. Other wise they may crack and crumble over time.
Add crushed gravel
You can also pick up crushed gravel to put in the bottom of the pier hole. The crushed gravel allows water to drain under the pier and it also gives more stability. Now is also a good time to pick up the Simpson strong ties and a spool of metal wire. I would also recommend getting a laser level which you will need very soon in the project.
Crushed gravel and tamp
Start by putting 4” of crushed gravel at the bottom of each pier hole. Use a tamp to compress the crushed gravel down and flat. Put a concrete form tube into each hole.
Highest elevation pier
You want to find the pier hole that has the highest elevation of all the other piers. You may think your land is flat but it can have inclined just so slightly. Land is rarely completely flat. It may be obvious just from looking at the grid of holes which one is at the highest elevation in the yard. From this highest tube you will make the measurements for all of the other tubes.
How off the ground should a pier and beam house be?
A pier and beam should be at least 6 inches off the ground at the lowest point of the house. If the area you are building is not flat it will be higher off the ground at lower elevations.
Find the highest elevation pier for your DIY pier and beam foundation
You want to figure out how low to the ground you want to the lowest point of the house to be. The highest elevation pier also will naturally be the lowest point of the house to the ground and the shortest pier. At lower elevations the piers will stick out out of the ground more to make up for the decline, leaving more open space under the house.
Start with the shortest pier
Since we are staring with the shortest pier that is at the highest elevation we want to make sure it is high enough off the ground. We also don’t want it to be too high off the ground as that will cause the taller piers at the lower elevations to be too tall. I would recommend that the highest elevation pier should be no shorter than 6 inches tall.
How tall can a pier and beam foundation be?
The tallest a pier should stick out of the ground no more than 3 feet. This is because the taller the pier becomes the less stable it becomes.
My DIY pier and beam foundation
In my scenario I had a very slight decline in my yard. My piers on the highest elevation were 6 inches tall. The piers on the lowest elevation were 1.5 foot tall. Meaning over the span of the house there was a 1 foot drop in elevation. I chose this height because I wanted the shortest pier to the ground be at least 6 inches tall.
Separation from the ground
This will give it good separation from the ground. This means the wood posts sitting on the cement pier won’t get splashed with water or dirt. Wet posts rot which causes structural issues, even pressure treated posts.
Be Wary of Wind Gusts
On the lowest elevation and tallest piers I thought 1.5 feet tall wasn’t too far out of the ground. You don’t want the pier to be sticking too far out of the ground. This could leave lots of space under the house for wind to get up under and cause issues. In my area we get 50 MPH wind gusts and I didn’t want a gust to structurally compromise the foundation. When you build a DIY pier and beam foundation it needs to be prepared for your areas weather.
Skirting
If you are building on a piece of land that is very hilly you will need to add skirting. This will cover the large spaces created under the house to prevent wind damage. Skirting will also keep out pesky rodents and other creatures. I personally don’t have any skirting because my land is relatively flat and I have wood stored under the house.
Find the Highest Elevation Pier
Go to the highest elevation pier and make sure it is both level on top and plum up and down. Take a measuring tape and measure 6 inches off the ground or whatever height you have decided. I made a mark on the form tube around the circumference at 6 inches off the ground.
Pull the tube out of the hole and use a saw or knife to cut the concrete form tube at the marking. Put the tube back in the hole after cutting and measure again. If you are satisfied with the measurement you can fill dirt in around the concrete form tube. Make sure the tube is still level on top and plum up and down.
How do I make level measurements on concrete form tubes for DIY pier and beam foundation?
Make markings with laser level
From this first tube you will make the measurements to cut all the other tubes. This will ensure everything is level and in line. What I did is put a laser level on top of the first cut pier its laser shining down the row of pier tubes. It’s best to wait until it is night or dusk to make any measurements. This is because the laser light will be more visible in the dark.
Make markings down the row
If it’s aligned with the top of the first cut pier and laser level is level. The laser marking down the row of piers will be level and parallel with the first pier you cut. Go down the row making markings in pencil on each concrete form tube. Make sure the markings are level go round the circumference of the form tube.
You may need to move the laser level to another pier to get all the piers measured. Make sure the new position you choose is level with the original marking.
Double check your work with a string line
After you mark all the form tubes with a pencil go back the next day when it is day time and double check your work. You can do this by running a string line along the measurement you made the night before. Use a longer level along the string line to double check everything is level. Make sure all measurements are made when the form tube is standing completely straight up, level on the top and plum.
Cut the concrete form tubes
Triple check or quadruple check everything and make sure all of the measurements look accurate. If you are comfortable with your measurements you can start cutting the tubes with a saw or knife. When you are done with all the tubes again double check that the tops of the cut tubes are level. You can use the string line you ran before and double check with with the laser level again.
Straight Rows
Now that the tubes are the right height next you wanna make sure they are straight as well. Run a string line over the rows of the form tubes. Make sure the string line runs somewhat through the center of each of pier tube. If its a little off its okay because you can move over the simpson strong tie over when pouring the concrete.
Check each row the direction the future posts will run. If the tubes are level and straight start to fill and tamp down the dirt around the pier tube. This will assure the tube is secured in place and won’t move while pouring the concrete in the form tube.
Conclusion: DIY pier and beam foundation
Building a DIY pier and beam foundation is easy when the right steps and planning are made. We are now ready to pour the concrete into the form tubes.
Next step: DIY Pier and Beam Foundation: Pouring Concrete
More resources: https://www.houseplans.com/blog/how-to-choose-the-right-foundation-for-your-new-house