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Framing systems for teachers’ union office

Wood framing is a conventional building practice that we use quite frequently at Endeavour. For the teachers’ union project, we are using wood framing for both the floor system and the exterior walls. The walls and floors may not look very different from conventional building, but from a sustainability point of view we’ve made choices that can make a large impact.

First, all the wood framing is certified by the Forest Stewardship Council (FSC), a third party certification organization that helps to ensure that wood products are harvested and processed according to high standards of sustainability. For this project, ensuring FSC certification meant going straight to a FSC certified distributor for our framing lumber and plywood as non of the local lumber yards are FSC certified.

The floor framing uses open web joists from TriForce. These open web joists do not use metal plates, but are finger-jointed and glued, using 2×3 top and bottom chords and 2×2 webs. This uses wood from smaller diameter, fast-growing trees and significantly less wood than solid floor joists, and significantly less glues than wooden I-beams with solid OSB centres. The floor joists are deep enough to allow us to achieve R-46 once they are filled with cellulose insulation.

The 2×6 wall framing is the load bearing exterior wall of the building, and will also be filled with cellulose, adding R-22 to the exterior of our bale walls (more on this hybrid system later), which will be installed to the interior side of the frame.

One of the great advantages of wood framing is the speed of construction and the low cost. When added to the renewability of wood when harvested and processed responsibility, it’s a great combination.

Earthbag foundation for floor system

In addition to the Durisol stem wall foundation, our project for the teachers’ union office includes two long sections of earthbag foundation to support the floor joist spans inside the building. The inherent insulation value of the Durisol blocks made them our first choice for the exterior of the building, but the extremely low environmental impact of earthbag foundations made them an easy choice for the interior.

Using continuous rolls of polypropylene bag material (this material would be cut and sewn to make rice, grain and feed bags) as a form for a variation of a rammed earth mix, earthbag is simple, durable and low cost.

A wide variety of material can be used in the bags, as long as it has an aggregate content capable of being tamped to a high degree of compaction. For this project, we used a road-base gravel and a small amount of a lime/metakaolin binder (you can read about this mixture here) to provide a mixture that tamps well and stays coherent after curing, even if the bag is damaged or removed. It is also possible to use aggregate and clay in the bags.

To facilitate the use of the continuous tubing, we built an earthbag loader based on a design by Kaki Hunter and Doni Kiffmeyer (authors of the excellent book, Earthbag Building), which uses a maple syrup bucket with the bottom removed and an insert made from a length of sonno-tube. The tubing is pulled onto the sonno-tube like a giant sock, with the “toe” of the sock pulled through the hole in the bucket. The pressure between the sonno-tube and the bucket prevents the tubing from continuing to pull through, unless the person loading the bags lifts the sonno-tube to allow more slack into the bag.

The material is added into the tube until the “shookler” (that’s a technical term!) determines that the desired amount of material is in the tube, and more tube is released. Behind the shookler is a tamper, who applies the tamping force that compresses the material until it has reached its limit and the proper level. We use a laser level to ensure that the top of the bag is at a consistent height.

Between each course of earthbag, a run of barbed wire is used to prevent the bags from sliding against one another. In the case of this building, we required three courses of earthbag. This was topped with a 2×8 sill plate on which the floor joists will be fastened. The sill plate is attached to the bags with long spikes as well as tie straps at regular intervals.

Though the process of doing earthbag can seem labour intensive, as a crew gets practiced it goes very quickly. Because there is no requirement for advanced formwork, it can actually be very competitive with forming and placing concrete. With a day’s practice, our crew was producing over 1.5 feet of finished bag per minute!

The beauty of earthbag is its simplicity. Bag material and fill as well as all the required tools can be found in almost any location in the world, and the strength and durability of earthbag foundations (or entire buildings) is remarkable. Bag on!

Helical pier foundation

The timber frame portion of our project for the teachers’ union rests outside the walls of the building, requiring individual foundation piers for each of the 14 posts. Typically, these would be poured concrete piers each with its own wide footing, resulting in a lot of concrete use and a lot of labour time to dig, form and pour each pier.

As an attractive option to digging and pouring concrete, we decided to use helical piers. This type of foundation is essentially a “ground screw,” consisting of a thick-walled metal tube with a screw plate on the tip. The helical piers are wound into the ground using a hydraulic device attached to a small backhoe. The screw plates are driven down to a depth below frost level and until the hydraulic force required to wind them reaches a pre-determined amount of torque. Once the proper torque has been achieved, the plates have sufficient bearing capacity to handle the loads that will be imposed on them.

Our piers were supplied and installed by Postech Peterborough. They were sized according to the engineered loads provided on our building plans. On the ground, we provided the layout points for the piers and their crew came and performed the installation.

Despite accurate points on the ground for the piers, the piers do not necessarily enter the ground perfectly straight so the tops can sometimes be off line even if the piers were started at the right point. This happened on several of our piers, so next time around, we would definitely make sure we had batter boards and string lines ready so the tops of the piers could be accurately aligned.

The piers are left long, and we cut them to height after the installation. A wide range of pier caps can be used depending on the type of post or beam being attached. Most of the caps use a threaded rod to allow for fine adjustment of the pier height.

One of the advantages of helical piers is there is no digging required, meaning that the site is barely disturbed. The installation of our 14 piers took about 5 hours, making it a quick process. The piers are ready for use immediately upon completion. The galvanized steel used for the piers is a high embodied energy material, but relatively little material is needed compared to concrete or other alternatives.

A Durisol stem wall foundation

Over the past few years, we have turned to Durisol insulated concrete forms (ICFs) several times. They offer an attractive blend of sustainable features with the convenience of conventional methodology.

For the teachers’ union office project, we needed a short stem wall to raise the walls of the building a suitable height above grade. There is no basement, and the footing is a shallow, frost protected perimeter beam, so the stem wall is only 2 feet tall. Durisol blocks provided us with a solution that worked well for several reasons. The blocks have a high insulation value (R-21 to R-28), are made from a very high percentage of recycled content, and are produced within a reasonable distance of our building site. They form a 5.5-inch concrete wall, using much less concrete than a full foundation wall (typically 8-12 inches wide).

 

In addition, the blocks come in several widths which for this building meant that we could use the 14-inch wide blocks as the first course and 12-inch wide blocks on the second course, leaving us with a 2-inch lip on which we could rest our floor joists. By keeping the floor joists within the insulated walls, we minimize thermal bridging and simplify air tightness at this important seam.

The Durisol blocks are dry stacked on the footing and on each course, making them very fast to install. They can be cut with a regular circular saw when necessary, and take a wood screw very securely. For our curved foundation, we did not attempt to cut the blocks to match the curve. Rather, we set them so the inside edges were touching on the curve and used a site-mixed hempcrete to fill in the gaps.

A lime-cement plaster is used to coat the exterior of the blocks, and we used a water-based, no-VOC liquid rubber and a 100% recycled content plastic dimple mat to complete the waterproofing layers on the exterior.

While this foundation wall still has relatively high embodied energy (due to its cement content), its energy efficiency, the lack of foam products, durability and the ease of construction make it an excellent option.

A unique shallow frost-protected foundation (SFPF)

In the pursuit of foundations that use little or no concrete, we have two common strategies that we often use. The first is rubble trench foundations (you can see an example here), and the second is shallow frost protected foundations (SFPF). Our extremely flat and low lying site this year dictated the use of a shallow foundation to avoid potential drainage issues in a deep trench.

The teachers’ union office building has two extensive curved sections in the foundation, and this would have made a conventional footing formed with 2×8 lumber difficult to achieve. A great new product called Fastfoot allowed us to make this footing very quickly and easily, and is a product we’d definitely use again. Made from a woven polypropylene, the Fastfoot uses lightweight stakes in the ground and small dimension lumber fastened to the stakes to support a fabric formwork (in many ways similar to doing earthbag footings) into which concrete is poured.

The Fastfoot system has several advantages over conventional formwork. We were able to use lightweight stakes and 2x4s (or doubled 1x4s to achieve the curves), despite the footing being 8 inches deep, rather than needing 2×8 lumber. As the formwork is draped by the Fastfoot fabric, the footing lumber does not get covered in concrete. This means when the forms are disassembled we can reuse the lumber without having to clean it. The fabric of the Fastfoot system is also a barrier to rising dampness from the soil beneath, adding a layer of protection from underneath. We were able to wrap the “tails” of the fabric up and over the footing and tie it into the foundation wall moisture proofing layers, adding a positive lap to the intersection between footing and stem wall.

The lines stamped onto the Fastfoot fabric make it easy to line up within the forms, and allow for many different widths of footing. There is no waste with the system, as the fabric stays in place. Joints in the fabric are overlapped by about a foot, and a folding pattern allows for corners to be handled easily. Our curves required us to make folds at regular intervals, and this too was easily done.

We had a few small issues when we poured the concrete into the form and had the fabric slide to one side under the force of the concrete. This pushed the fabric out on one side and left a concave section on the other. In these areas we had to shovel the concrete a bit to get the form centred again. We wouldn’t make that mistake again as it’s easily avoided.

Fastfoot is an excellent addition to our sustainable building toolbox.

Off-grid job site power system

Many sustainable building projects are built in places where it is difficult or impossible to access electrical grid power, and this necessitates running a gasoline or diesel powered generator to provide power for tools. Over the course of an entire building project this can add up to a lot of fossil fuel… I have records from one job that show we used 2,250 liters of gas over a five month period! Hard to be making claims about sustainable building when that much fossil fuel is being burned in the process.

Despite our project for the teachers’ union being in a very urban location, there was no accessible grid power and we did not want to run a generator again. The cost of running a temporary electrical service (including utility fees and electrician’s time) was around $2500, and then there would be charges for the power used on top of that.

We spoke with Sean Flanagan of Flanagan and Sun about a PV (photovoltaic) based system that could run our job site, and the price tag was about $3800. More than the temporary power, but once built the system could be used again and again in the future. Our clients at the Trillium Lakelands Elementary Teachers’ Union generously agreed to put the budgeted cost of temporary power toward the system, clearing the way for the Sustainable New Construction class of 2014 to be powered by renewable energy!


The system features 480 watts of photovoltaic output, and is coupled with two large deep cycle batteries and a 3,000 watt sine wave inverter to provide power to the tools. A MPPT (maximum power point tracking) charge controller is the “brains” of the system, matching the amount of charge from the panels to the needs of the batteries.

After trouble shooting through some issues with the first charge controller (wrong unit for the PV voltage), our site now runs on 100% renewable energy, without the noise and pollution and cost of running a generator. We do face some limitations… if multiple tools try to start up at exactly the same moment the breaker on the inverter will trip. On a cloudy day with the air compressor running almost constantly, we can have difficulty running other tools. But living within limited means is all part of sustainable building and living, and it’s a good lesson to be reminded of during construction.

The silence and the clean air are well worth the small sacrifices. We’d encourage other builders to consider similar systems. The system is small enough to fit in a typical tool trailer, and we’ve also known builders to carry the batteries and inverter in their trucks, using the truck’s alternator to also charge the batteries as they drive to and from the job site. If each project can eliminate the need for hundreds of liters of fossil fuel, that would be a worthwhile impact!

Timber frame for teachers’ union

Timber framing is an important building system for any sustainable builders’ palette of options, and we always try to include a timber framing element in our projects so our students can gain some exposure and experience in this time-honoured way of building.

Our current project features five “bents” or timber frame sections. Four of them hold up the roof over the curved ends of the building, allowing the roof to be straight, square and simple while the walls follow a rounded path. One bent holds up an entry roof section.

The timber frame section from the building plans was reviewed by both our structural engineer (Tim Krahn of Building Alternatives) and our timber framing instructor (Mark Davidson of Whippletree Timber Framing). From Tim’s recommendations on timber sizing and Mark’s expertise at layout and joinery, the initial design was turned into working drawings for the frame.

From Mark’s layout sketches, we went to work on measuring, marking and cutting the joinery on the actual timbers. Mark showed the class the basics of square rule timber framing, introducing us to principles and techniques of using a framing square to achieve the layout.

Each bent consists of three posts supporting two beam sections (joined with a scarf cut) with four knee braces to provide shear support, and we made four identical bents for each corner of the building. Unlike classic timber frame structures, this frame does not support the roof for the whole building but shares the duties with the straight sections of structural wall.

After completing the marking, the joinery was cut using a combination of classic hand tools (saws and chisels) and power tools (circular saw, mortise cutter and drill). In general, the power tools made the big rough cuts and hand tools were used to clean up and refine the cuts to ensure tight, smooth joints. We then drilled the holes into the mortises for the pegs that will hold all the joints on the finished bents.

As the joints in each bent were completed, we arranged sawhorses so that the entire section could be test fit in a horizontal position. Some of the joints needed to be cleaned up a bit in order to assemble the bents, but once the test fit was successful the pieces were numbered and the frames disassembled until the foundation is ready to receive them.

Welcoming the Class of 2014!

Endeavour’s full-time Sustainable New Construction program is underway, marking the third year of this exciting immersion experience.

Trillium Lakelands Teachers' Union building

Rendering of the Trillium Lakelands ETFO building

This year’s class will be building a new office for the Trillium Lakelands local of the Elementary Teachers Federation of Ontario (ETFO), in downtown Lindsay, Ontario. The building will be featuring a rubble trench foundation with Durisol blocks and earthbag grade beams, a hybrid straw bale/frame wall system, all natural plasters and finishes, a Passive House-style heating system, 5kW of photovoltaics, composting toilets, solar hot water and much more!

Sustainable New Construction class of 2014

Sustainable New Construction class of 2014

The class brings a wide variety of backgrounds and come from as far afield as Ecuador and the United States, as well as Canadians from across the country. We’re thrilled to have (left to right) Lesley Fukumura (BC), Greyson Sherritt (Ontario), Kathleen Spencer (Quebec), Andy Fisher (Ontario), Ivonka Brehovska (Ontario), Ben Bowman (US), Dániaba Montesinos (Ecuador) and Neil Boyer (US) join us here in Peterborough.

We are excited to have this new group of students joining us at Endeavour. The program has been extended to 6 months this year, giving the class an extra month to ensure they get to see all the finishing materials and details.

Please be sure to follow our progress as we start to blog about the project!

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