Wheelbarrow is one Word.

Slab preparation requires a ton of physical work and is visually unrewarding. Last week I became much too familiar with the word wheelbarrow. The site is nearly flat, with a minor 8-inch grade change between the north and south side of the house. We had to add earth to the interior footprint to bring everything up to one level.

grade diagram

Because the CMU foundation wall is above grade, a bobcat cannot drive over the wall to move earth, so hauling is all done with a wheelbarrow. Bruce and I armed with shovels and wheelbarrows, backfilled and compacted the crusher fines in the trench and then worked our way towards the center of the building footprint.

Piles upon piles upon piles.
Piles upon piles upon piles.

After the interior grade was leveled and compacted, we laid down 48” wide rolls of Ayr-Foil over the entire footprint of the house. This step is satisfies code by insulating below the concrete slab. Recently Ayr-Foil replaced the foam board insulation code requirement. Trying to compact earth over foam is a Sisyphean task at best; foam, once released from pressure, springs back and disturbs compaction.

125' Ayr-Foil rolls.
125-foot rolls.

Ayr-Foil is similar to a sheet of bubble wrap, except that one side is coated in a layer of foil, (which, in theory, reflects the heat from the radiant flooring back into the concrete slab) and the other side is white. In truth, it is a delicate material, and it doesn’t have near the R-value of two inches of foam, but it satisfies the building code requirement.

Duct taping Ayr-Foil seams.
Duct taping Ayr-Foil seams.

While researching the spelling of Ayr-Foil, I stumbled upon their technical literature, and according the manufacturers, sub-slab applications should be laid with white side facing up and concrete poured directly on top. In Northern New Mexico the installation is done a little differently: Ayr-Foil Is laid foil side up, then two inches of crusher fines are compacted on top of the foil. The two inches of earth between foil and concrete achieves a couple of things; first, it provides mass, which retains heat from the radiant flooring, and second, it sets the concrete slab faster because the water in the concrete is both evaporated upward, and pulled downward into the compacted earth. If the concrete were to be poured directly on top of the Ayr-Foil the water would only be able to evaporate, and the concrete would cure much slower. Ayr-Foil laid foil side up, also makes sense, as it is the reflective side, which will come in contact with heat and be reflected back in to the slab.

To recap, the earth is leveled and compacted before and after Ayr-Foil. The following images are Greg and Weasel (Weas) covering 2,000 square feet of Ayr-Foil in 2-inches of crusher fines. Who needs the gym when you haul earth for a living!

Step 1.
Step 1.
Step 2.
Step 2.
Step 3.
Step 3.

Once all the earth is leveled it needs to be screeded, which is further fine-tuning. The screed that we used was a piece of 2×6 lumber guided by string lines.

Juan the perfectionist.
Juan the perfectionist.

By standing the 2x on edge and manually pulling the dirt with the lumber, so that the top of the wood is directly flush with the bottom of the string, you can get a surprisingly level substrate. To make sure all that hard work stays put the earth is hosed down. The weight of the wet dirt holds it in place and compacts it again.

 

Greg hydrating dirt.
Greg hydrating dirt.

Next came the plate compactor. Normally Weasels favorite task, unfortunately the machine we rented was on its last legs and was coughing a steady plume of noxious fumes into Weas’ face. It didn’t take him too long to make his way around the entire house, and I am sure he popped a beer immediately after just to wash the gassy flavor from his mouth.

Weas mowing his dirt lawn.
Weas mowing his dirt lawn.

After using the plate compactor we laid down sheets of metal mesh, 8-feet wide by 20-feet long. The mesh acts as slab reinforcement and provides an organizing grid for tying on the radiant tubing.

Metal mesh with 6-inch grid
Metal mesh with 6-inch grid
Patio with metal mesh.  Ready for Monday slab pour.
Patio with metal mesh. Ready for Monday slab pour.

 

While we were playing in the dirt the plumbers and the electricians were installing their rough-ins, which also take place in the dirt below the slab. This means that all locations of plumbing fixtures (sinks, toilets, baths, washers, water heaters) need to be finalized, and in the case of freestanding bathtubs, the exact model needs to be chosen. It seems early to be choosing final plumbing fixtures, but really it is important to design with their dimensions in mind, or at the last minute you will be frantically looking for a fixture that will fit into the space!

Plumbing.

A lot of jokes are told on the jobsite; this is one of my dad’s favorites:

Ed: “What are three things you need to know to be a Plumber?”

Me: “What.”

Ed: “Hot is on the left, payday is Friday, and shit runs downhill!

I am sure Jason and Jose, the Plumbers would disagree, but at this phase of the plumbing aka the “rough-in,” it is quite straightforward. It boils down to two different types of tube material. PVC and PEX. PVC is the large white pipe that carries wastewater and requires a slope of ¼” per foot to move solids. Anything less than that prevents solids from being flushed out by water and gravity, and anything steeper has difficulties flushing solids because the water flows out too quickly. PEX carries clean potable water to all the wet rooms in the house. It is also color coded: Red PEX = hot water, Blue PEX = cold water.

Manifold is another term frequently used at this stage of plumbing. The manifold ties all the PEX tubes together (hot with hot and cold with cold), so that they are on a continuous loop. The 1” diameter clear PEX pipe is the main supply line which delivers water to the smaller color-coded PEX.

Red PEX manifold.
Red PEX manifold.

All water enters the house through the mechanical room, which serves as the “heart of the home.” It stores the hot water heater, which is why it is the first point of contact for water.   The radiant flooring manifold is also in the mechanical room.   By locating everything in this room it is easy for plumbers to test the tubes for any punctures and to retrace their footsteps for any issues down the road.

Radiant flooring manifold.
Radiant flooring manifold.

The radiant flooring is also made out of PEX tubing, clear. It is tied onto the metal mesh and is directly set into the concrete flooring. Before laying out the tubing, zones need to be established. This means that you can turn on the radiant floor heating in different areas of the house. We set individual zones as follows:

RADIANT FLOOR DIAGRAM

While laying the tubing, closest to the perimeter, two continuous tubes are 6” apart from each other effectively creating a heat wall. Because most heat in a home is lost through windows and doors this acts as a buffer to heat loss. After the perimeter is laid tubing is space 12” apart and uncoiled toward the center of the zone.

Jason untangling PEX tubing.
Jason untangling PEX tubing.
Finished radiant flooring layout. Beautiful!
Finished radiant flooring layout. Beautiful!

The last step in the plumbing “rough-in”, are the “box-out’s”.  It is critical that we are able to access the PCV pipe once the slab is poured.

Duct taped white foam, acts as the "box-out." After the slab is poured we can pull the white foam and still have access to the plumbing.
Duct taped white foam, acts as the “box-out.” After the slab is poured we can pull the white foam and still have access to the plumbing.

Electricity.

Under slab electrical is small part of the whole house wiring, and services outlets that are floating in a room, for example an outlet in the floor or in a kitchen island. It must be installed before the slab is poured.

Sub slab electricity for kitchen island and living room floor outlet.
Sub slab electrical conduit for kitchen island and living room floor outlet (beyond).

We are using Maes Electric. Sound familiar? Same guys that do our earthwork. When Dan isn’t operating the bobcat he is an electrician. However they sent out Robert that day, Dan’s uncle, and his son Robert Jr. It’s all about Family aqui en Taos.

Robert Sr.
Robert Sr. 
Robert Jr.
Robert Jr.

Next Monday the first slab is getting poured. We had to tie-up a couple of loose ends before then.

Gil setting metal in trench for carport footer.
Gil setting metal in trench for carport footer.
Doorway "blocking" for slab pour.
Doorway “blocking” for slab pour.

P.S. We finally got the construction site signs up!

Signage.
Signage.

Foundation System

I have drawn this detail so many times, and never really understood how it was built… until now.

Click to enlarge.
Click to enlarge.

It is a standard foundation detail; one taught in school. However, I learn by experience, so it took building it to finally make sense.

The most confounding part of the detail was how the vertical rebar managed to stay in place, as the concrete footer was poured. It turns out, to be much simpler than I imagined: the concrete is poured, and THEN the pieces of vertical rebar are set into the footers. Fresh concrete is firm enough to hold rebar in place. I for some reason thought that concrete had a similar consistency to water, but its fluidity is incomparable, plus the aggregate in concrete helps keep rebar in place, and as it dries it becomes solid.

Week Two Recap: we dug the trenches, laid the continuous rebar, and placed chairs, spreaders, and vertical grade pins.

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Next, we poured the concrete footer.  This process began by spraying the trenches with water to slow down the concrete dehydration.

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We had a big group of guys there, and we needed every one of them.   Steve was controlling the pump arm; Gato was working the hose. Harvey was shoveling concrete into places the hose couldn’t reach. Bruce and Greg were tamping the concrete down to level. Juan was at the tail end making the surface smooth. I was taking pictures, and my dad was telling us all to “¡Jale´ Jale´!”

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The large concrete pump arm can reach 100’ feet – to the furthest corners – so we didn’t have to fill those trenches manually. The whole footer took us about two hours to pour, including placing the rebar. We were done by 9am.

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Gato and Harvey (the Masons) then went around the perimeter and placed the vertical rebar every 48” to support the CMU (concrete masonry unit) stem walls. They knew exactly where they wanted them.

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That all happened on Friday – end of week two.

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Week Three Recap:

Last week was incredibly productive and once again changed my perspective on the scale of the house. When we cleared the sagebrush I was concerned with the house being too small, and now that the CMU walls are in place, the house is starting to feel large again (the model always felt “big” to me). Last weekend I spoke with another woman, who worked in construction, and she mentioned, “ Throughout a project, certain phases will expand and contract space.” I was comforted to hear it, because so far it has been a wild ride, but apparently not unusual.

On Monday, Harvey and Gato set the “leads,” which are the CMU corners. We started with the corners, because they have to be exactly square and set at the right elevation, as the rest of the wall is dependent upon those being perfect. Harvey is sooooo good at this! His trowel and masons level are extensions of his arms; it is mesmerizing to watch.

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Staged block around perimeter of continuous trench.
Staged block around perimeter of continuous trench.

On Tuesday we filled in the walls. The guys let me lay two blocks – it was extremely difficult, and required ambidexterity. Needless to say, they had to redo my work.

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Almost done!
Almost done!

Wednesday, we had off. I forget why. Probably to let the blocks set.

Thursday, we poured concrete into the cells of the CMU block walls. This didn’t require as many people as the footer, and we used a much smaller hose. It was also a quick job.

Group effort.
Group effort.
Smaller concrete hose on ground.
Smaller concrete hose on ground.

At this stage we had to insert anchor bolts, every 6’ around wall, while the concrete was still wet. The anchor bolt, will anchor the framing to the foundation wall, once we get to that stage in the project.

Triangles drawn on block demarcate anchor bolt placement.
Triangles drawn on block demarcate anchor bolt placement.

And on Friday, Bruce and I had the pleasure of taping 2” rigid foam board to the exterior foundation wall, and then back filling it with dirt. Foam insulation is required by code, and is effective for preventing heat loss through the foundation.

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P.S. What my dad does when he is not being the Boss:

Ed meditatively chopping wood.
Ed meditatively chopping wood.

Earthwork

As with any profession, one must learn the language. Despite the similarities between architecture and construction, building vernacular is much more expansive; not only do you need to know what to call the finished product, for example, “footers,” but you also need to know the parts required to make that product: batter boards, alligator clips, string lines, builders level, lime, sister-boards, “burning one,” chairs, wire twister, stakes, trench… I could go on. I don’t want to bore you with every definition, but most important in this phase of the project are batter boards, not to be confused with “board & batten,” this I know from experience.

Board and Batten Siding – vertical wooden strips hide and protect the board’s seams.
Board and Batten Siding – vertical wooden strips hide and protect the board’s seams.

Batter boards are located via the “Big Rectangle.” After picking a corner from the Big Rectangle the “building lines” are measured out, in two directions, and the batter boards are located. They are made out of scrap 2×4’s and metal stakes, and are critical for getting the building square. They are also used for setting the height of the slab, but that is a conversation for another day.

Our batter board and string layout. Does this make sense?
Our batter board and string layout.

Below is another simplified diagram, (not this project) which shows the batter boards in perspective. batter-boards-drawing1

Mr. Ed and Weasel discussing their fine batter board craftsmanship.
Mr. Ed and Weasel discussing their fine batter board craftsmanship.

The grey areas in both diagrams are where the trenches are located, although they will be wider, approximately the width of a 16” bobcat bucket. While digging the trenches, the “building line” string is rolled up, to accommodate the bobcat, and later unrolled to double check that the trench is straight. It’s not fool proof, and we had a good deal of hand digging that day to get the trenches linear. I am still sore. Because the string lines are rolled up, the bobcat operator uses the lime line (white powder), to guide his excavation.

Lime Lines
Lime Lines

It has been expressed to me, on many occasions and by many people, the large number of corners in this project – sixteen to be exact. They are particularly difficult to dig out with a bobcat, so I definitely made Dan sweat that day. At one point he even dug himself into a corner.

Dan the Man digging trenches.
Dan the Man digging trenches.
Mounds!
Mounds!
Bacon-Shark needed a break after moving all that earth!
Bacon-Shark needed a break after moving all that earth!

After the trenches were dug, we laid the rebar. This sits permanently in the bottom half of the concrete footer and acts as a unifying strengthener. A few things one should know about rebar:

  • It should not touch the earth, which is why the horizontal rebar sits on plastic “chairs”. Water from the earth will corrode it, and it will not pass inspection.
  • Every 4’ there is a vertical grade pin, which sets the height of the footer. This is the only piece that can touch the ground, because if it rusts it will not the sacrifice the integrity of the structure. It also can’t touch any other piece of rebar because rust transmits through contact.
  • Every 4’ there is a spreader, to keep the width consistent between the long runs of rebar.
  • Rule of thumb: to find the amount of rebar length to overlap, multiply the diameter of the rebar by 40. For example ½” diameter rebar x 40 = 20 inches (of overlap).
  • Rebar has to be 3” away from the edge of the concrete, in any direction.
  • The tool used to tie the rebar together with wire is called a “wire twister.” Go figure.
  • A piece of rebar is set into the concrete footer and travels up into the framed wall to act as a lightening ground. This is in most houses.
Rebar on Plastic Chairs
Rebar on Plastic Chairs

We passed the trenching and rebar inspection on Thursday, so concrete footers are in our near future. P.S. correction to well drilling process: The client was kind enough to inform me of my misunderstanding of the well-drilling process, so I have drawn this diagram to better illustrate the steps of reaching the water table; critical for habitation out on the dry mesa! WELL DIAGRAM