Craving Structure - Part 2

Now that we have an outer 'envelope' we begin on the inner structure: another more heavily-insulated box designed to meet specific needs. Our box is eight feet tall, 12 feet wide and attaches to the end walls making it approximately fifty feet long.

 

Metal wall studs mount to a track anchored to the concrete slab.

The outer wall is set about 10" inside the Quonset wall to allow for the roof curve which begins at about five feet above the slab. 

Track runs about 10" inside Quonset wall to allow for roof curve.

End column shows how wall and roof curve comes together.

In our plan we chose not to insulate between the rooms. All plumbing and electrical is standard design. The ventilation is custom designed for our passive system.

Using traditional materials in nontraditional ways keeps our costs down and allows us to find bargains otherwise not available.

Interior walls go up.

All exterior walls have 3" insulation making each room within the structure very cost-effective to heat or cool. Heavy-duty rafters provide ample storage space above.

An 18-inch overhang allows additional storage space without compromising floor space.

 Our plan to use LED lighting makes wiring and electrical fixtures easy to obtain and accommodate.

Craving Structure - Part 1

Although an 'envelope' structure's inner and outer skins are largely independent, they are connected at doors and windows and may have other connecting elements.

Commonly referred to as an 'envelope' structure, this type of construction may be accomplished with almost any system: pole barn, traditional metal building, or Quonset. It is essentially a building with independent inner and outer skins.

Furring strips applied to the Galvalume arches.

In our application, The outer skin features 3/4" EPS insulation glued to 1"x 4" EPS furring strips. The big challenge here was finding an adhesive that would hold the EPS to the Galvalume but not cavitate (melt) the EPS.

The furring strip gives a good base for mounting the EPS panels while solving the problem of dealing with the Quonset bolts. This method also adds about 12 square inches to each 'ducts' cross section.

After much research and trial and error, we located a company that produces a contact-type adhesive that works flawlessly.

Contact adhesive is applied to the 4' x 16' x 3/4" insulation panels and pressed into place.

After a few minutes drying time, the insulation panels can be installed.

The bottom run of panels complete, we are ready to start the second run. Note the open space at the bottom.

We used 3/4"-thick panels to allow a smooth fit inside the curved Quonset arches.

EPS panels easily form to the curve of the Quonset Hut arches.

Space at the bottom of the panels is left open to allow cooler, moist air to be pulled into the ventilation 'ducts' and lifted to the exhaust plenum at the roof ridge along the top of the building.

This photo gives an excellent illustration of the 'duct' formed by the Quonset ridge and the EPS insulation.

Water Management

Water run-off quickly fills the channel and leaks into the building.

One unique challenge with a Quonset is water-proofing the base. If left as constructed, the U-Channel base plate will catch and hold water as it runs off the roof, and, trust me, a lot of water runs off the roof! There are two problems with handling the water: first, diverting the water away from the channel; and second, stopping the water from running between the channel and the slab. When the base plates were put down, grout was used between the channel and the concrete. 

Concrete fill is a cheap, quick, and easy way to divert the run-off away from the base.

After the arches were erected the pockets were filled with concrete. It’s important to coat the Galvalume Quonset panels with a protectant before the concrete is put into place. To simplify the concrete application, we put Sakrete in dry, then poured water over the top. This way it is easier to deal with, rather than having to mix a bag for each pour.  

After the concrete sets, a good quality caulk helps seal the joint between the concrete and the Galvalume skin.

After the pockets were filled with concrete, the edges were caulked and a thin coat of water-proof cement was troweled over it. After the water-proof cement cured we used concrete sealer over it all for good measure.

The Beginning of the Ends

My apologies for the delay in posting. We’ve made good progress in spite of a two-month recovery from a fall that resulted in torn ligaments in both shoulders. It’s difficult to do construction work when you can’t raise your arms above waist-high. But I digress. 

The front of the Quonset has two bi-fold doors.

The photos will tell the story of where we are.  Both ends are up and waiting for the trim and finish. When complete, the whole building will be insulated. Both end walls are paneled with Hardi-board and have 3” insulation. The bi-folds are fourteen feet tall and sixteen feet wide. They were custom built on site using heavy-duty metal studs. The hinges are roller bearings and they ride on 3” heavy duty rollers. This route was chosen because a commercially-available door of the same size is four to five times the cost. 

The back of the building has a single four-by-eight foot door.

The rear access door is also built on site, but using lighter metal studs. The two-by-six foot opening at the top on both ends is the exhaust for our passive convection air circulation system.

Filling out the Form

View from the inside.

With the last arch in place, the crew starts back at the beginning and inserts any missing bolts and tightening everything down. It's amazing to see how the simple act of tightening bolts brings all the arches in line and smooths out the form.

View from the south end.

Working toward completion, we received delivery of our insulation panels and were able to stack them inside the structure. That kept them from melting in the noonday Florida sun.

The stretch bars (see on the side) are a critical part of the equation. Proper application (READ THE INSTRUCTIONS) keeps everything lined up so that one side of the building isn’t a foot-and-a-half longer than the other when you get to the end! 

There’s a line of stretch bars on the top also, but to elaborate would seem redundant.

Allowing for monsoons, and breaking midday for a few hours to avoid being vaporized by the Florida sun, we completed our mission in just six days.

Up she goes!

Bundles of corrugated steel and buckets of bolts, a building make.

Weatherstripping on all joints keeps the water out.

Okay, kiddies, this is what a 40-foot by 50-foot Quonset hut looks like before you add water. Alright, so you don’t add water…just a few thousand bolts… and a few miles of weather-proofing tape doesn’t hurt, either.

A heavy-duty impact drill makes this step fast and easy.

Before the arches go up, the base plates must be anchored. After careful measuring, we drilled half-inch holes about 8 inches deep with a an impact drill. The anchors are half-inch by six-inch Red Head concrete anchors. They work great and can be reasonably purchased from any fastener supply dealer.

As they say: “A journey of a thousand miles begins with one step, and a Quonset hut begins with one arch”. Okay, I added that part about the Quonset hut...and it’s only partially true. A Quonset hut actually begins by bolting two sections together but the most important part of that step is identifying which two sections belong to each other.  

Keep plenty of drill batteries on hand and powered up.

To do this, it helps to have at least one member of the crew who can not only read, but has the proper motivation to do so.  They give you written instructions for a reason: to help you figure out where you screwed up after you realize the knowledge of proper Quonset hut building is NOT in your DNA!

Regardless which method and equipment you choose to raise your first arch, it is the most challenging one to put in place.

This view shows how flexible a single arch is. 

After employing the alternative strategy, I strongly urge you to READ THE INSTRUCTIONS FIRST!

Oh, another thing; Never underestimate the flexibility of a Quonset arch. The more hands you have, the better (and safer) the process will be. We thought we had what it took to get the first arch up, and we did…but my life flashed before my eyes three times before it was securely perched on the scaffold jacks. After putting our first arch up in one piece, we wisely decided to do the rest in half sections and I had no more ’life-flashes’.

Half sections were much easier to work with. This photo shows us with three-and-a-half arches up.

As you can see, things went fairly smoothly from this point, and as each arch wormed its way into place, they actually seemed to get easier. 

Finalizing the Slab Forms

The following pictures show the final stages of completing the slab and footing forms. This step includes utility stub-ups, placement of reinforcing bars (rebar), welded wire mesh, and the foam inserts used to form the cistern gutters.

Mrs. Q checks the stub-ups and moisture barrier.

The crew assembles the cistern gutter form.

 A footing corner showing the cistern gutter form, rebar, and geo-tube

A side benefit of the Quonset's construction is its highly efficient precipitation run-off. The galvalume metal finish is very smooth and since the roof and walls are a continuous corrugated plane, all of the moisture that falls on the building is directed quickly to the gutters which drain into the cistern. In areas where snow is a possibility, heavier live-load specifications are required.

If it snows here, we're moving to Cuba!

The concrete trucks arrive early and the action begins. Concrete was pumped into place in parts of the slab because the trucks couldn't get into a position to pour.

The morning sun greets the cement trucks.

The cistern gutters begin to take shape.

A cement finisher forms a slope to the drain.

Cement begins to harden within a half hour, so the men work fast to get everything in place.

Using the long trowel pole, a finisher works the concrete.

Seven truck loads of cement later, the slab is formed and takes on a smooth finish. Finish troweling burnishes any imperfections and after a couple of days of curing, stress grooves will be cut to minimize cracking. Our contractor assured us, however, that concrete cracks, but with all these precautions they should be minor hairlines. Within three to four days, we'll be ready for the Quonset shell to be erected!