Weather Barrier

The weather barrier for the tiny house is a fluid applied product by Prosoco. The product, an equivalent of $1500, was donated to us by the company there by securing our first sponsor! 

The tiny home weather barrier is comprised of a series of three R-Guard products from Prosoco, a construction products manufacturer:

R-Guard: Joint and seam filler (fiber reinforced fill coat and seam treatment)

R-Guard: FastFlash (liquid flashing membrane)

R-Guard: Cat 5 (air and waterproof barrier)

Our motivations for using the Prosoco R-Guard weather barrier system over a more standard house wrap, like Tyvek, had to do with the aesthetic and assembly of the tiny home's exterior rainscreen system. The rainscreen will be comprised of thin, vertically-oriented timbers, sealed using the Japanese shou sugi ban method of charring and blackening the wood. There will be a 1/2" gap between these vertical timbers, revealing whatever weather barrier condition lies behind it. Tyvek would, of course, stand out starkly from behind the black rainscreen timbers and compromise the exterior aesthetic. We need a dark, recessive weather barrier, and Prosoco's 'dark bronze' Cat 5 product suits our needs perfectly.

These products have been used in numerous projects by Studio 804 at the University of Kansas School of Architecture and Design and was recommended to us. We had the pleasure (and luck) of being in close proximity to a local product rep who was very generous in advising us on the proper applications of the product.

Above: Application of the R-Guard joint and seam filler over an exterior OSB joint. The product is applied generously from a tube and then evenly distributed using a putty knife. The joint and seam filler was applied to all exterior joints and corners, including the roof. It was also applied on over-driven screws that created recesses in the OSB surface.

Above: Application of the R-Guard FastFlash at a window opening. Similar to the joint and seam filler, the product is applied generously from a tube and then evenly distributed using a putty knife, The FastFlash was applied to all window and door openings, including skylights. The material is quite viscous and has a build of 3/16" once applied. The product was applied, like flashing, to the depth of the window and to the OSB surface immediately surrounding it, but not to any surfaces at the interior of the tiny home. 

 Window with FastFlash Applied

Window with FastFlash Applied

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Above: The application of the joint and seam filler and FastFlash had to be done on separate days, as the products each take about a day to dry. 

In preparation to apply the Cat 5 air and weather barrier, we removed all of the product stickers on the surface of the OSB sheets (this would not have been a problem had we installed the sheathing with the smooth surface on the inside).

The Cat 5, which comes in large buckets, was applied to the exterior walls in a single day, using paint rollers (it was not applied to the roof because roofs us underpayment that is more durable for asphalt shingles, metal standing seam, or roof tiles). The material should be applied heavily, leaving the finished coat thick and consistent, with no OSB, joint and seam filler, or FastFlash visible. In our first application, the material had not been copious enough in some places and had to be covered with a second coat two days later once the first coat had dried.

The material must be mixed well before each use, and a tarp should be laid under all edges where applied, as it drips heavily while it dries. We found that our paint rollers had to be thrown out after each use, so an optimized work flow is encouraged, rather than a piecemeal one. Special care should be taken to protect your hands and body: wear long sleeves, pants, and latex gloves but keep in mind that they can ruin clothes and stain your skin temporarily. 

Overall, we are exceedingly satisfied with this product in terms of ease of application, functionality, and aesthetic. An added advantage that we had not anticipated was the product's behavior as a natural binding agent for the exterior sheathing, further reinforcing the rigidity of the tiny home. 

Sheathing

 Before sheathing

Before sheathing

The process of sheathing the tiny home was conducted with material optimization and ease of construction as top priorities, using full OSB sheets where possible and minimizing cuts on all other sheets. We used 48"x96"x.4375" OSB sheets and secured them with 1.25" drywall screws.

The exterior sheathing brought an impressive level of lateral stability to the tiny home structure; the tiny home now has no sway or deflection, as it did before the sheathing was applied.

 West Wall

West Wall

 South Wall

South Wall

Panels on the walls were staggered and oriented horizontally in order to 'bind' 4' framing modules together, giving added stability to the wall framing. The same principle was applied to the roof, with panels staggered and oriented in the long direction of the roof to 'bind' framing modules together; however, we used .5" thick panels as we rafters were 24" on-center. This logic breaks occasionally, such as at the South wall, where the panels around the window were sized to line up with the clear opening, using the largest panel sizes possible and avoiding complicated cuts.

At the perimeter of each sheet, screws were applied on 8" centers, while screws were applied on 12" centers in the middle of the sheet where vertical studs were located.

Smooth face of OSB oriented to the exterior face was a mistake but not a fatal one. The other side of the OSB is rough and has vertical and horizontal lines for nailing and screwing lines (we now know that).

 All walls sheathed

All walls sheathed

The exterior sheathing for the walls and roof was applied in a single day with three people. The use of ladders and scaffolding were essential to the safe and clean installation of the wall panels, while a forklift was very useful in getting OSB sheets safely onto the roof. 

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The installation of the sheathing gave us the first sense of interior enclosure within the tiny home. The space was surprisingly much as we had imagined it, and the amount of light permitted by the window and door openings seemed highly conducive to the sense of openness and natural lighting we had intended. 

 Fully Sheathed Exterior

Fully Sheathed Exterior

 Fully Sheathed Interior

Fully Sheathed Interior

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For the roof sheathing, we used sheathing clips. They helped in aligning the panels in both direction and maintain consistent expansion gaps. In hindsight, using clips on the walls would be a highly recommend process. The clips also help secure on panel to another for added wind assisted panel tear. 

Roof Framing

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The framing of the roof was the most challenging tiny home construction exercise to date; this was due primarily to the unique geometry around cutting and the need to be elevated during installation. Our friend, Ian, spent an entire day with us installing and troubleshooting the roof framing. Kadim had done all of the cutting of the rafters the day before.

While we did have scaffolding, a fork lift, and ladders available to us, the process of installation was considerably ad hoc, and we finally developed confidence and the best installation methods by the time we reached the final roof rafter.

 Ian was rightfully skeptical of Kadim's temporary lateral bracing techniques.

Ian was rightfully skeptical of Kadim's temporary lateral bracing techniques.

 Considerable attention to detail was required in order to install and align the roof rafters in coordination with the 2x10 columns. 

Considerable attention to detail was required in order to install and align the roof rafters in coordination with the 2x10 columns. 

 Again, the skepticism. Again, justified.

Again, the skepticism. Again, justified.

The roof installation at the loft end was reasonably smooth, due to the fixed, elevated surface that could allow the roof connections to be easily accessed and managed. The floor surfaces had not yet been installed in the other parts of the tiny home, so coordinating ladders and tools was one of the largest parts of the roof installation effort, not to mention elevating each 2"x6"x10' roof timber. 

 Strategizing, and probably exchanging snarky remarks.

Strategizing, and probably exchanging snarky remarks.

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Before the installation of the rafters, the walls were considerably insecure; one good push and pull would have the entire house swaying. However, once the rafters were installed, the entire skeleton became much more rigid, and we expect that the exterior and interior sheathing will give it full rigidity and structural soundness.

Wall Framing

The wall framing for the tiny home consisted of 800+ linear feet of dimensional lumber and was executed in only three days between lumber delivery, cutting, dry laying, nailing, and erecting. 

 Lumber delivery + our friend, Adam.

Lumber delivery + our friend, Adam.

 Lumber delivery continued...

Lumber delivery continued...

 Ian and Yahya beginning to tackle 800+ linear feet of cutting. 

Ian and Yahya beginning to tackle 800+ linear feet of cutting. 

The weekend dedicated to framing the walls was our most productive use of help from friends. Because tasks were generally repetitive and did not require intimate knowledge of the tiny home design, we could get people going on cutting or drilling as we coordinated and delegated. Our friend, Ian, and Kadim's brother, Yahya, spent a full day cutting all of the lumber for the wall framing as I provided them with dimensions and helped them coordinate cuts that would result in the least amount of waste. 

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As the cutting was underway, I began dry laying the wall framing in order to keep track of cuts and anticipate nailing and framing patterns. We chose to frame the walls in 4' modules comprised of 2x4" lumber; these modules would fit between the larger 2x8" columns that separated each structural bay in the tiny home. By doing this, we could ensure that nailing would be carefully executed, and once each module was complete, it could be lifted into place and installed without the use of machinery or very much muscle. 

 Door module.

Door module.

 Window module.

Window module.

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As shown in the images above, we (Kadim) eventually discovered that nailing on top of the trailer was much easier on the back than nailing on the floor.

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In the image above and the two below is a mock-up of the detail Kadim developed for the way in which the wall framing and the interior floor sheathing meet. The wall sandwich is comprised of 2x4" lumber, sheathed with 7/16" osb on either side. The floor sheathing is 3/4" osb. 

A 3" strip of 3/4" osb mediates between the floor rim joists and the base plate of the wall framing. The 3/4" gap left on the interior allows the interior floor modules to be slid into place and their edge condition disguised underneath the wall framing. The bottom edge of the interior wall sheathing is chamfered to allow the floor panel to be slotted easily into place and to mitigate damage at the edge of the interior osb, which is the wall finish. 

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After our team of friends had finished helping us cut the wall framing lumber and began nailing walls, Kadim and I were able to finish the nailing in a day, and we erected all 14 walls on our own in a single day in only 3.5 hours. It was tedious work, but had we not made the walls out of 4' modules, we would not have been able to erect them ourselves without considerable help and coordination. 

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 Wall framing complete, with a few temporary lateral braces.

Wall framing complete, with a few temporary lateral braces.

Floor Framing

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The framing of the raised floor system was our first true construction task for the tiny home. We went to Menard's and hand-selected each piece of 2x10" lumber for the beams and joists, each sheet of 7/16" OSB (oriented strand board) for the sheathing at the underside of the floor frame, and each sheet of 3/4" OSB for the floor finish.

Our construction strategy involved building the entire floor framing in three large sections on the ground and then lifting them into place on the trailer frame, where the sections would be bolted to each other and to the trailer frame itself. As shown in the series of photos in the blog post below, this strategy allows the framing to be easily maneuvered for squaring and nailing, and allows the underside sheathing to be screwed into place from above.

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As trained architects, we are very familiar with making precise and well-crafted objects, and we are reasonably familiar with power tools and the design and coordination of structures and systems; however, the framing of the first floor section proved that our familiarity with construction techniques and tolerances was considerably lacking. After all the framing lumber was cut to size according to our digital model, our first construction hurdle involved getting the framing squared. For this we ended up using a metal angle and some temporary bracing, as shown in the images above; the attachment of the underside sheathing, validated the squareness of the framing. 

The 2x10" framing members were nailed together, while the 7/16" OSB underside sheathing was screwed onto the framing. The construction of the floor framing involved basic tools, such as tape measures, pencils, metal angles, and clamps, and power tools such as a circular saw, table saw, nail gun, and drill. 

We first constructed the 4' bathroom section of the floor and then the 8' kitchen and entry section of the floor and lifted them into their respective locations at either end of the trailer. The 8' kitchen and entry floor section is shown in the middle two images above; the gaps in underside sheathing are for the water tank and battery bank storage compartments integrated in the trailer framing below the raised timber floor system. 

The three images below show the construction of the final 12' floor section at the center of the floor system where the trailer wheel hubs are located. 

The row of images below show the final 12' floor section being lifted and positioned onto the trailer. As made evident by the images, the floor sections were incredibly heavy and difficult to maneuver, requiring four people to relocate them from floor to trailer. 

After getting the final floor section onto the trailer, we found it impossible to fit all three sections flush on the top of the trailer. This was the result of measuring and building the floor system according to our digital model, rather from the measurements of the built trailer; the trailer apparently had a few dimensional discrepancies relative to what we had specified in our drawings to the trailer manufacturer. This resulted in two hours of four strong men forcing the floor sections into place via jumping and sledge hammering, as shown in the right-hand images below. While this was exceedingly frustrating, it was admittedly equally amusing.

The biggest lessons learned in the framing of the floor were to check built dimensions, to build with tolerances, and that construction can be a bit messy and unpredictable, regardless of any amount of prior planning. 

In the end, the floor framing was successfully installed, with each section squared and sitting flush against the trailer and against the adjacent section(s). 

While some tiny homes opt to use the trailer framing itself as the floor framing, we chose to employ a raised floor system for a few reasons. Firstly, a raised floor system allows us to route plumbing and electrical through it. Secondly, nearly half of our raised floor system serves as under-floor storage, with all compartments 9" deep, and typically 30x20" in length and width; the remaining raised floor system compartments are insulated, with insulation for the in-floor storage zones located within the trailer framing below. Finally, the raised floor system, which is flush with the top of the trailer wheel hubs, allows us to avoid the trailer wheel hubs as an eyesore and impediment to efficient interior space planning. The greatest setback to the raised floor system is that it reduces the clear height of the interior volume; if we had opted not to have a 10" raised floor, we could've likely gained 10" in ceiling height, which would've been an enormous asset in the lofted sleeping area.

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