Building our Foundation 2: Pouring Concrete Pads.
The second post in our "Building a Foundation" series, about how we prepared and poured concrete pads for our foundation.
Laying our Foundation was a HUGE undertaking, so I've broken the process into several posts. This is the 2nd post and it covers the 2nd step, preparing and pouring cement pads. If you haven't read the first post in this series I suggest starting there.
In the last post on building our foundation I explained how we planned our grid, and marked the positions of the cement pads. The next step is to pour our concrete pads, which will act as a base to build our foundation supports on.
The steps to prepare and pour our concrete pads are:
Build Wooden Frames to Pour the Cement Into
Position and level each frame
Mix the cement
Pour concrete into the frame and level surface
1. Build Wooden Frames to Pour the Cement Into
The first step to pour our cement pads was to build wooden frames to pour the cement into. The wooden frames act as a mold, the cement will be poured into the frame and allowed to dry. The result will be a solid cement pad in the shape of the frame. First we had to decide on the dimensions we wanted for the cement pads.
We decided to use scrap 2"x 6"lumber, meaning our cement pads would be ~6" thick. We needed to be able to place 2 cinder blocks side by side, cinder blocks are 8"x 16", so we determined 18"x 18" pads would suffice.
For an internal dimension of 18"x 18" you will need to cut your lumber 20" (18" + 2"thickness of lumber). At the time of constructing the frames we only had a skill saw (hand-held circular saw), but I would recommend using a mitre saw with a stand.
Before you cut enough wood to make all of your frames, make one and measure it. This way if you need to adjust your cut length you haven't wasted a days work and a load of lumber.
I measured 4 pieces of lumber 20" long and cut them. Then I laid out the lumber on the ground to determine how I would put it together, I landed on the configuration in the photo below.
Next the tedious part, I nailed together the 4 pieces of wood at the corners to finish the frame. I used 3.5" nails. Once assembled, I measured the frame to ensure the dimensions were correct. 1 Frame down, only 34 left!
My recommendations for making the frames:
Setup a miter saw (on a table or stand) to save your back when cutting the lumber
Make all of your cuts and stack the pieces of wood in sets of 4
Setup a low bench to help with the assembly. I placed a couple 10' lengths of 2x6 across 2 cinder blocks for a make-shift bench.
Work in sets of 5 or 10, it helps if you can focus on making a few and then take a break
Use scrap pieces of wood to prop up the frame when you are nailing the sides together
Wear safety glasses when cutting, and always wear steal toe work boots
Crank the music up (Let's Rock- The Black Keys was my choice)
Stay hydrated with a healthy mix of water and beer
I'm going to guess it took me about 5-6 hours to put together 35 frames, but at the time I had virtually no experience swinging a hammer. Also I used a skill saw, which i would NOT recommend. You could probably get this done much faster than me, I am as slow as molasses.
2. Position and Level Each Frame
This next part was the first of many times over the next few months I swore "Why the F*** are we building such a massive cabin?". Putting 1 frame down is neither physically difficult or tedious, but 35 frames? If you have a bad back I would not recommend this task, and if you don't have a bad back now, you will for a week after this.
I had already marked the location for each of the cement pads (previous post) however, I needed to do three things to prepare the frame for pouring cement
Position the frame to line up with where the stringer support will be
Level the frame
Surround the frame with rocks to form a seal between the frame and ground
To position the frames located within the cabin perimeter I ensured the center of the frame was lined up with the marker for the cement pad location. For the frames on the corners of the cabin I positioned the center of the frame to be inside of the corner (where the 2 strings intersect). You can see the positioning in the photo below.
Note: After pouring our pads we realized we should have positioned the pads inside the perimeter to protect the foundation supports from rain/snow. This is why we ended up extending our cabin 6" on each end, so the cabin is 47' long instead of the original 46'.
Leveling the frames was more difficult, thanks to our extremely rocky land. That is why they call Newfoundland "The Rock" after all. Using a steel shovel and rake I leveled out the area for the frame as best I could. Then I placed the frame in position and hammered it down with a mallet. Then I ran a level across the top of the frame, in both directions, to see how level it was.
To adjust the leveling of the frame I had to either remove rocks or add rocks under the frame to prop it up. Once the frame was relatively level, I pushed rock and dirt against the base of the frame, on both the inside and outside of the frame. This holds the frame in place and will also prevent the cement from leaking out of the mold.
3. Mix the Cement to form Concrete
We were extremely lucky and were able to borrow a cement mixer for the day for free. But you can mix the cement by hand in a wheelbarrow, it will be harder but it is doable. Also, if you have the money and road access you can pay a cement truck to bring a load of mixed cement... not necessary though if you are only pouring a small volume.
First we calculated the total volume of mixed concrete we needed, by multiplying the volume of each frame by the number of frames. Then we called a local cement/concrete business and asked them how many bags of dry cement we would need, they also told us how much sand/gravel we would need to add. Cement and sand is expensive and heavy to bring to a remote location, so it is a good idea to talk to someone experienced so you don't over-purchase.
In total we purchased ~10 bags of cement and 2 pick-up loads of course sand. We worked in batches, mixing one bag of cement at a time. We weren't very exact with our mix ratios but we aimed for a thick consistency, adjusting the mix as we worked. I recommend checking out some you-tube videos for a more detailed explanation of the process.
We started by adding ~8 gallons of water to the mixer and turning it on. Then we added a bag of cement and let it mix until combined. Then we started shoveling our course sand (or gravel) into the mixer, allowing it to mix between shovelfuls until we achieved a thick consistency.
Once we were happy with the mix we poured some into the wheelbarrow and then turned the mixer back on while we worked. A couple of times we poured the mix in the wheelbarrow it looked too runny so we added some more sand and mixed with a shovel.
4. Pour the Concrete into the Frame and Level Surface
Sorry for the lack of pictures during this part of the process, once we started mixing cement we had to work fast and our hands got messy! This was the easiest and most satisfying part of the process.
We used a shovel to fill each frame with concrete, we filled all the way to the top edge of the frame. Then we dragged a piece of 2x4 across the top edge of the frame, leveling out the top surface of the wet concrete. We repeated this in both directions, sometimes adding extra cement, to ensure we had a flat and level surface.
Mike and I finished about 5 concrete pads with one batch from the mixer in about a half an hour. It started to rain and it was getting late so we called it quits for the day.
The next day our friend Jason gave us a hand and we finished all the concrete pads in less than 2 hours! The weekend was over and we had to go back to work so we had plenty of time for the concrete to cure before we continued building our foundation.
The foundation build continues next in Building our Foundation 3: Supporting and Leveling Stringer Beams.
Disclaimer: We are not design professionals or carpenters. The purpose of these posts is to share how we did it, but by no means take what you read here as design or construction advise. Always do your own research, talk to professionals, and follow local codes/regulations.