Ground Floor Girder and Joist Installation

Our project is ready for the ground floor girder and joist installation over the fully-insulated, conditioned crawlspace. Engineered Parallam girders and TJI joists are specified for their superior span length, uniformity and use of Oriented Strand lumber milling by-products, a sustainable materials characteristic.

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The piers supporting the floor girders stick up over the crawlspace floor level. To maintain a continuous air and vapor seal they are capped with 10mil poly sheeting and taped. After posts and girders are installed they will be insulated with spray foam together with the rim joists and mud sills to eliminate any thermal bridging.

1 3/4″ Laminated Veneer Lumber (LVL) is specified by the structural engineer for the rim joists. Check out the anchor bolts connecting the building frame to the foundation …over 150 total. Earthquake country!

The plumber has run the underfloor plumbing which will be insulated before the subfloor is installed. The Drain/Waste/Vent piping extends through the building shell to the exterior so it is really a part of the thermal envelope of the building and therefore should be insulated to eliminate thermal bridging.

The hot water lines also get super thick 1″ insulation through the main supply trunk loop and up into the walls all the way to the fixture.

The subfloor is screwed and glued with a super-strong, Green Guard certified low VOC polyurethane adhesive compatible with the engineered AdvanTech flooring.

Ready for a dance. Walls next …about time.

Copper Termite Shield

A copper termite shield is installed around the entire foundation. It may be expensive now but a good investment when compared to the damage termites can cost a homeowner over the lifetime of the house.

The copper flange is screwed into the plastic web of the ICFs to secure it before finishing the wall with a top coat of hard stucco.

Galvanized metal could have been used but would have lasted 20 years at the very most with some serious rust along the way. Copper will last the life of the building, or at least 100 years.

Crawlspace Drainage System

In the middle of the crawlspace floor area on top of the building pad we place a perforated drain pipe with gravel and cover it with filter fabric.

The perorated drain pipe is installed with a T-fitting to connect a surface drain for the finished concrete floor of the crawlspace.

The 3″ drain pipe from the floor drain to the outside of the foundation wall is non-perforated and sloped so that any surface water from the crawlspace floor from a severe plumbing leak or flood …or good hose out …will drain to the exterior where it terminates in a dry sump fifteen feet away from the house.

A 3-4 inch layer of drain rock is then backfilled into the entire crawlspace.

Any bulk water intrusion whether flood or otherwise will quickly drain out.

The crawlspace is now ready for a sturdy vapor barrier.

Moisture Management of the Crawlspace – Gravel Base

As designers and builders of high-performance homes, we believe in buildings that will remain durable over a long time (like 100 years or more at a minimum). Persistent moisture on wood will eventually lead to rot and failure of joists, sills and posts. Moisture also creates an ideal environment for mold, mildew and fungus which causes poor indoor air quality. Keeping everything dry is the single most important element of durable, healthy buildings.

Our starting point is the installation of gravel below the insulated crawlspace floor so there is a drainage plane underneath the building. Later we install a perimeter drainage system around the exterior foundation walls, but here we are first concerned with the interior area. We installed about 22 cubic yards of 3/4″ drain rock, or a depth of 3 to 4″ throughout the crawlspace.

Our bobcat delivers the gravel from the street to our crawlspace floor.

Freddy spreads the gravel evenly thoughout the space.

Any moisture that might accumulate under the foundation will channel to the drain. See another story about the crawlspace drain.

The first layer of our moisture-managed foundation is completed. On to Step 2: The Vapor Barrier.

Moisture Management of the Crawlspace: The Vapor Barrier

To protect the house from water vapor entering the crawlspace by evaporation of water contained in moist soil, we cover the gravel base with a high performance vapor barrier. The materials are made using virgin high density polyethylene . This bright yellow product is calledStegoWrap. It’s a tough 10 mils thick and very puncture resistant.

Most crawl spaces are not constructed with vapor barriers and consequently are subject to several gallons a day of water evaporating from the damp soil below. This is the reason that most older crawlspaces are vented by building code so that all that water vapor will be removed from under the house by natural air flow through the crawlspace vents. The trouble is that often there are too few vents, they are blocked or poorly sized and positioned such that the area stays damp…not good.

By installing a vapor barrier none of that water vapor ever enters the crawlspace in the first place.

To be effective, a vapor barrier must be continuous so we overlap the seams by a foot or two and use pressure sensitive tape for airtight sealing of all seams and the perimeter attachment to the foundation wall.

We also drill weep holes in the floor drain riser so that if any moisture does happen to collect on top of the vapor barrier it will weep out the drain.

We are now air, water and water vapor tight with a gravel drainage plane below and floor drain above. This meets the EPA’s tough Indoor Air Plus specification for water-managed foundations and crawlspaces. We are ready to insulate the floor.

Crawlspace Insulation – Expanded Polystyrene (EPS) Foam Insulation

To achieve superior thermal performance, durability and protection from the elements our crawl space floor is a multi-layered assembly. First, the space was filled with 4 inches of gravel for drainage, followed by heavy duty polyethylene sheeting as a vapor barrier. The third layer is 3″ thick expanded polystyrene (EPS) foam sheeting for insulation.

Custom cutting EPS to fit our crawl space floor is relatively easy.

A tight fit is the goal.

We are using a high density EPS (2#) for strength so that we can pour a 2.5″ to 3″ slab of concrete over the top to protect the EPS and provide a highly durable, drainable and cleanable surface for finished crawlspace floor.

The completed crawlspace floor assembly will have a modelled insulation value of over R14. This definitely helps meet the Passive House thermal envelope requirements. We are on our way to passing the “heat it with a hair dryer” test!

Because EPS (expanded polystyrene) is mostly air, it makes an excellent insulator. The thousands of air pockets create a very effective thermal barrier. EPS is very stable and maintains almost 100% of its original R-Value over time which helps in fulfilling our goal of building for durability. 100% of the EPS can be recycled. Since the Insulated Concrete Forms are also made from EPS that means the whole crawlspace can be recycled …in a few hundred years. 🙂 Now on to Step 4.

Moisture Management of the Crawlspace: Concrete Floor

After the four inch gravel layer, sealed poly sheeting and rigid EPS foam insulation we finish off our crawlspace with a three inch thick layer of concrete. Concrete not only protects the foam but also protects the the house from termites and other pests.

The concrete topping slab has a slight grade so that it will drain from front to back where there is a floor drain. This is great for floods and the occasional hose out.

After four layers of protective coatings and barriers, our house will be very well insulated and isolated from the detrimental effects of moisture, insects, rodents and soil gas for a very long time.

Starting the Pier and Grade Beam Foundation.

In our earthquake prone region of Northern California, building codes are incredibly strict and complex. This particular site has a high content of sand and the building codes require that we take the foundation piers to a depth of 11′.

The piers support the load of the building and prevent the foundation from settling.

Rebar structure for the piers.

Ready to pour the piers.

Foundation Grade Beams

The beams trasfer the vertical load imposed on the span (or middle) of the beams to the concrete piers.

Cardboard forms placed at the bottom of the trench decompose and create a void which prevents unwanted uplift on the grade beams.

A conditioned crawl space will be constructed above and allow us to insulate the structure from moisture and cold ground temperatures from the sub-soil.

High Performance Foundation Technology: Insulating Concrete Forms (ICF).

High Performance Foundation Technology: Insulating Concrete Forms (ICF).

We are building our foundation walls using Insulating Concrete Forms (ICF) which are rigid plastic foam (EPS – Expanded Polystryrene) forms that hold concrete in place during curing. The ICFs remain in place to serve as thermal insulation for the concrete foundation walls.  These ICFs are made by Greenblock and have an R-value of about 22.

The ICFs have plastic webs every six inches for strength and for tying the two walls of EPS foam together. Rebar is placed and tied to the webs as we place layers of ICF blocks together… kind of like Legos!

Once the concrete has cured, ICFs form an incredibly strong structure that is permanent and durable. Since the protective insulation provides an ideal curing environment, tests conducted by the Portland Cement Association have shown that concrete is up to 50% stronger than concrete cured in traditional wood form systems.

We brace as we stack anticipating the pressure from the concrete pour. The ICF’s will be pumped full with a soupy concrete mixture held to a 5″-6″ slump.

Pre-manufactured 45- and 90-degree corners and a precision alignment system helps to adjust the walls to ensure a perfectly square and plumb structure.

The same system is used for the attached garage.

Our crew has laid rebar horizontally and vertically inside the ICF’s to create a structurally sound unit designed for the expected vertical and lateral loading conditions according to the structural engineer’s specs. This is earthquake country so there is lots of steel!

It’s time to call for the concrete.