Construction - Insulating the Earth Contact North Wall

Intentional Compromise
In a perfect world, the earth contact north wall would have been a full two stories high, i.e., at least 16 feet.  But to have done so would have increased its cost so significantly that I decided to stop at 12' with the concrete and carry the wall to second story height with a short truss wall.  The latter could be done with salvaged lumber and my free labor as opposed to paying for professional labor and buying several more yards of concrete to increase the height, not just of the 12" thick wall itself, but the three substantial deadmen behind the wall as well.

Moreover, it will be easier with the truss wall to achieve an R-48+ to match the other external truss walls than to insulate a concrete wall to this R-value.  But the advantages of a higher wall of concrete would have been an additional 200 sq ft of earth contact for the AGS system and more of the wall totally impenetrable by air infiltration/exfiltration. However, I am betting that (a) the large floor area of the house, (b) the +/-10' of uninsulated north earth contact wall, (c) a partial earth contact west wall and (d) the insulation/watershed umbrella will provide all of the insulated and dry thermal mass the house will ever need without the additional 4' of concrete for the north wall.  Therefore, I think the additional 200 sq ft of earth contact would have been expensive insurance for a problem that probably does not exist.

Tweaking the Platon Damp-Proofing 
As described in a prior post, the Platon damp-proofing system was used on the lower 8' of

Original Platon installation

the tall section of the wall before backfilling began.  The top 4' still needed damp-proofing before it could be insulated.  I decided to keep the Platon system below the bottom of the metal channel that holds the insulation. Otherwise, the extra bulk would cause unevenness of the insulation because the top of the channel would be directly against the concrete and the bottom would hang over the bulky Platon material. Consequently, I installed only enough additional Platon to bridge the gap between the original material and the bottom of the channel.  As will become apparent presently, the two layers of plastic sheeting that waterproofs the metal channels and insulation will also waterproof the concrete even better than would the Platon material.  The exception to this arrangement was the first four feet at the ends of the wall where the insulation extended down nearly 6' behind what will eventually be retaining walls running more or less perpendicular to the wall.  Here the channels did overlay the Platon material and did flare out somewhat at the bottom.

Materials Preparation
First is was necessary to calculate how far the insulation should extend below the mudsill of the truss wall.  Code specifies a distance of 8" between the grade and the mudsill. Figuring downward from the mudsill, the first 8" will be exposed stucco, the topsoil over the

insulation/watershed umbrella will be 8" deep and the umbrella will be 6-7" thick, so the wall must be insulated to a depth of at least 23" below the mudsill to get below the umbrella. (Below that, of course, the wall should remain uninsulated so that heat can pass back and forth through the wall between the earth and the living space as a function of the AGS system.  For more on AGS, click on the "Featured Post" in the column at the left.)  I settled on 32" of insulation 3 1/2" thick for an R-14 to a depth of 8-9" below the bottom of the umbrella. The nearby photo shows these dimensions drawn on the cement board before stuccoing (click on the photo to enlarge it for better detail).

Parenthetically, in order to achieve an overall R-48, the inside of the wall will have to be insulated to another R-34, which is the subject of a future post.

I used a plywood blade in a circular saw to cut two thicknesses of expanded polystyrene foam board -- 2" and 1 1/2" -- into 24" x 32" pieces .  I also cut 
3 5/8" wide 20 gauge galvanized steel channel (the kind that is used as the top and bottom plates for steel studs for wall framing) into 24" lengths using a metal blade in a radial arm saw.  I cut 1/2" cement board into 48" x 28" pieces using a corded fibercement nibbler.  Next, I cut lengths of 6 mil plastic sheeting into 8' wide pieces.  At this point, all I needed in order to begin insulating the wall were 1 1/4" x 3/8" Tapcon screws for fastening the channels to the wall and 1 1/4" cement board screws with high-low threads for fastening the cement board to the outside of the channels.  I then followed the same installation procedures that were covered in a previous post with a few deviations that were so minor as not to warrant special discussion here.

Installing the Insulation
As described in the previous post, the channels were readied for installation in the shop by cutting to length, drilling holes for the Tapcon screws in half of the channels and then screwing channels with holes back-to-back with channels without holes.  I started the installation at the east (left) end of the 12' wall so that the channel with the holes would be facing to the right each time so as to make it easier to use the hammer drill in my right hand; if I were left-handed, I would have started at the other end of the wall.

The first four feet of the wall needed to be insulated to a depth of +/-6'.  The additional depth was necessitated by the transition from an 8' wall to a 12' wall which will be accomplished by a retaining wall running more or less perpendicular to the wall and butted up against the first four feet of insulation.  (The first book on earth sheltering that I read some 8-9 years ago was Rob Roy's Earth Sheltered Houses in which he cautioned against butting a retaining wall against the concrete house wall without insulation between the two in order to reduce heat loss and to eliminate moisture condensation during warm months.) The same 4 x 6' configuration was necessary at the west end of the wall for another retaining wall.  In between, there was a span of approximately 52' where the insulation was only 32" in height.

Before the channel and the insulation could be started, the 6 mill plastic had to be positioned so that roughly half of it would be trapped under the insulation and half lapped

Insulation installed on about half of the wall with the inner
layer of plastic showing beyond and below the foam;
 bare concrete is in the distance; notice that the metal
 channels are shorter than the insulation

over the insulation, completely sealing off the channel-insulation complex. The rolls of plastic I buy at the farm supply store comes 24' x 100'.  I divided the 24' dimension into thirds.  The 8' wide pieces provided 4' of plastic between the insulation and the concrete wall and 4' between the insulation and the cement board. And the individual pieces of plastic were overlapped by a couple of feet.  In this way, the metal channels were totally sealed against rust-inducing moisture, rather than relying solely on galvanization, and the concrete wall was not just damp-proofed but was actually waterproofed in the process.

Without going into all of the details covered in the previous post, the installation was a

Completed installation of the foam; notice the outer layer
of sheet plastic, thrown back and weighted down on the
floor of the scaffold, that will be brought forward and
 draped over the foam before the cement board goes on 

matter of screwing a pair of channels to the wall over the inner layer of plastic, mating a piece of 2" foam board with a piece 1 1/2" thick, slipping the left side of the foam into the channel, slipping the next pair of channels over the right side of the foam and applying pressure leftward while drilling the holes and inserting the Tapcon screws. The 32" length for the foam and 24"length for the metal meant that the foam protruded below the foam 7-8" in order to keep the metal well up inside the sheet plastic to keep it dry.  I also kept the tops of the channels an inch or so below the tops ot the foam in order to keep any rough edges from perforating the sheet plastic. The inside diameter of the channels is 3 5/8" and the foam is 3 1/2" thick so there is enough tolerance that the insulation can be moved somewhat.  Accordingly, after all of the insulation was in place, I used a mason line to level the tops of the foam to match the bottom of the mudsill that will eventually hang over them.  Any remaining gaps between the sill and the foam board will eventually be sealed with mortar as described in a subsequent post.

Installing the Cement Board
Installation of the cement board required two cordless drills and a driver for phillips head cement board screws.   Before taking a piece of cement board to the wall, I used one drill

Completed cement board installation; notice ample outer
 layer plastic sheeting exposed below the board; the
backfill will press it against the edge of the foam and
the wall below to seal the channel/foam assembly against
moisture

with a 3/16" masonry bit to drill a hole in the upper left corner and the upper right corner.  I As soon as the left side of the board was butted against the right side of the previous piece, aligned flush with the top of it and proved level with a torpedo level, I used the second drill with a bit designed for metal to drill a pilot hole in the metal track through the hole previously drilled in the board in the upper left corner. Then, while holding the board steady, I used the driver to fasten the board to the track with a cement board screw.  The remainder of the screws could then be installed in a similar manner, i.e., masonry bit, metal bit and cement board screw.

Installation of the cement board is best done by two people because it is heavy and difficult to manage working alone.  I overcame the problem by leaning a 2 x 4 against the wall at the level of the bottom of the board as a support.  However, the rest was rarely at the right height necessitating a lot of juggling which probable quadrupled the installation time.  It didn't help either that the ground was uneven and snow-covered part of the time and beginning to thaw the rest of the time.  In either case, the slipperiness underfoot made things interesting.

Stuccoing the Cement Board
This last step in insulating the concrete wall followed exactly the procedures described in detail in the previous post.  The only difference was it had to be done in late December instead of warm weather, which complicated and slowed the process considerably.  Not knowing when the stuccoing might get done, I am publishing this post without pictures of the stucco on the assumption that the curious will be checking out the previous post anyway.

Honest Perspective
The DIY concrete wall insulation described here and in the previous post is a good example of a green building approach that would not be practical in a production setting because it is too customized, cobbled together from disparate materials and time-consuming.  In a way, though, it is a microcosm of our entire house project.  Jo Scheer in the book, Eco Architecture says, "Though extreme eco-architecture may not be a solution to a thoroughly sustainable building industry, it certainly provides ideas. It is a model of ideas and concepts that beg to be assimilated".  Who knows what impact on sustainability some of our "impractical" ideas might have somewhere down the line.  

Construction - First Exterior Truss Wall

The actual "first" exterior wall was described in the previous post  but its ten-foot-plus height from the second story floor and a preponderance of windows caused it to be a hybrid instead of a pure truss wall.  The wall described here provides an opportunity to detail the building of an 8' wall using trusses made ahead of time in a jig. Rather than going over the details of truss wall construction when blogging on the rest of the exterior walls, I will link back to this post as a reference.

The wall is the exterior wall between the garage and the living quarters.  By not having windows like most of the other stick-built exterior walls, it allows us to focus on the use of trusses instead of 2 x 4s or 2 x 6s for framing.  The fact that it has a door only means that a couple of trusses are positioned differently than would be the case for a plain wall.  While the garage will be insulated and passively conditioned to a higher comfort level than most garages, the design for the wall is no different than for the rest of the exterior walls, i.e., 15" thick and an R-value of just under 50.

Although I intend to refer back to this post in the future for the details of truss wall construction, it is atypical in one respect.  The wall was put together on the floor of the garage and tipped to place from the exterior side.  The remaining truss walls will be assembled on the house floor and tipped up from the interior.  I will try to nuance the difference during this narrative.

Building the Wall
I took eleven trusses for the wall from the stash of pre-made trusses and built the wall on the floor as is typical of most wall construction.  I failed to photograph the wall while it was laying on the floor so I've included the following photo from the most recent post as an example of horizontal assemblage.  

After cutting the 2 x 6 pressure-treated bottom plates (mud sills) and the salvaged lumber 2 x 6 top plates to length, I laid them side-by-side and used a tape measure to mark lay-out lines on 24" centers as if laying out stud positions for traditional walls. The future pedestrian door to the garage was laid out in the process, centered over the mini-ramp that had been formed into the garage floor to make the doorway ADA compliant.  I stood the trusses on edge in the approximate positions they would occupy in the lay-out. I stood straight pressure-treated 2 x 6s on edge against the bottom of the trusses with the lay-out lines facing the trusses.  The trusses were moved to match the lay-out lines more closely and "eye-balled" perpendicular to the 2 x 6 longitudinally. Then, starting at one end, I aligned each truss accurately with its lay-out line on the mud sill and nailed it with one nail.  I then used a rafter square to make sure the truss was perpendicular to the sill before adding more nails.  

Digressing for a moment.  The rest of the 8' exterior walls will be framed on the floor of the house as opposed to the garage floor.  For them, getting the framing as flush as possible on the interior profile for smoother drywall would be more important than for the sheathing and cladding side of the wall. So, the following procedure applies specifically to the other walls but I used it for this wall while knowing that any minor discrepancies would be reversed and face inward and the garage wall would be the smoothest. A smooth interior profile is another reason for using the straightest 2 x 6s next to the floor which puts them on the interior side when the wall is raised.  

I slipped enough shim(s) under the 2 x 6 and the end of the truss for the truss and the 2 x 6 to be in simultaneous contact with the shim(s) before sending home the first nail  Since the trusses, having been assembled in a jig, are quite true and uniform, the shims merely compensate for any unevenness in the floor that might cause misalignment of the straight 2 x 6 with the trusses and result in a rougher interior profile.

The next step was to attach the interior-most (current situation; exterior-most for the rest of the walls) top plates in exactly the same manner.  (I use the plural form "plates" because the pressure treated 2 x 6s would have had to have measured 20' to have spanned the entire length of the wall.  It is hard to find straight pressure treated two-by-sixes this long so, I used two boards of varying lengths for each plate so that the junction between them on one side of the wall did not fall opposite the junction on the other side of the wall.  The top plates were salvage lumber so I used two of varying lengths such that the junction of one set of top plates were staggered not only with each other but with those of the bottom plates. 

Finally, it was a simple job to nail the second set of 2 x 6s to the trusses.  The trusses were already properly aligned as for perpendicularity and therefore already matched the layout lines on the top plates.  Although the 2 x 6s were salvaged lumber, the two used for the exterior-most top plate were pretty straight while the one of them used for the inner top plate was bowed slightly.  I made sure the bow was facing towards the center of the wall so that it would not hang over the top of the wall and interfere with proper mating to the floor joist as described below.  For the other walls, a plate that bowed outward would make for bumpy drywall or sheathing so I have made it a practice to fasten all crooked plates with the convex profile facing inward towards the middle of the wall.  Since the second set of plates had to be suspended while nailing, I cut spacers to fit over the plates nearest the floor that held them in place but slightly too low.  Then it was a matter of shimming them a little into a nailing position flush with the edge of the truss.

Only one other job remained before the wall was ready to raise.  I scabbed together the segmented plates with short boards and drywall screws.  This maneuver stiffened the wall for raising; the scabs were removed later.  In fact, one of the scabs interfered with proper placement of a truss so its installation was delayed until after the wall was raised and the scab had been removed.

The wall aligned, secured and ready for covering (click on the image
to enlarge it for more detail)

Raising and Aligning the Wall
I used a spirit level to check the north concrete wall and the south truss wall and found that they were both plumb.  Therefore, I could use the distance between them at the floor as the measurement for the length for the wall while allowing a 1/4" tolerance.  The three guys helping me raise the wall were skeptical about such a close tolerance only to have to witness me puffing up and strutting around when it went to place exactly as planned.  

After it was in place, I secured the top by clamping it to the adjacent floor joist to which it would eventually be nailed after the wall was aligned.  The wall had no choice but to be plumb in a north-south direction as it fit tightly against the concrete north wall and the truss south wall.  And fitting against the floor joist took care of its straightness at the top. All that remained for alignment was getting it plumb in an east-west direction after fastening it to the joist.  Plumbing also automatically aligned the bottom longitudinally. The top of the wall ended up being pretty level despite the concrete floor being anything but (see Major Concern below).  Minor differences will be handled as the rest of the rake wall is stick-built on top of it. 

Fastening the Wall To Place
I nailed the top of the wall to the second story floor joist and to the existing south wall. Fastening to the joist took the place of a second layer of 2 x 6s commonly found in double top plates to bridge over joints in the first layer and to tie together intersecting walls.  The need for a double top plate was further diminished by having two top plates side-by-side to begin with.

I fastened pressure treated two-bys to the north concrete wall with robust (1/4") Tapcon screws and nailed the north end of the new wall to them.  I supported any gaps between the bottom plates and the insulated concrete foundation or the concrete floor with composite shims under each truss.  I then used the 1/2" galvanized anchor bolts, that were installed into the top of the foundation when the concrete was poured, to tie down the bottom of the wall.  Because one of the bolts fell in the doorway and had to be cut off, there were only three bolts for the entire wall so I added three more using 1/2" concrete anchors.

Shielding the Wall from the Weather
Since the trusses have gussets made from interior plywood and OSB board and, since my

snail-paced construction schedule means they will be exposed to rain and snow unduly long, I immediately covered the wall with lumber wraps.  I expected to be using relatively expensive 6 mil plastic sheeting (at nearly $100 for a 100' x 24' roll) until realizing that the lumber wraps were free for the asking from my local lumber yard.  I used a lot of staples and a few batten boards to fasten the wrap. How well it resists the wind remains to be seen.  At least I get to test it on this short and easily-accessible wall before using it for the tall wall described in the previous post.

The inside to the left also needed covering

Looming Problem
The concrete floor on which the wall sets is not level, in one area being 1/2" out of level over a distance of only 6' or so.  Nor is the concrete foundation perfectly level within itself or level with the floor in many places.  Consequently, there were some serious spaces under the bottom plates that have to be air-sealed in some manner.  At the time of this writing, I am not entirely sure how to do it, whether to use mortar or spray foam or caulk or ???????.

This will be a common problem for all of the exterior walls so I will have much to say about it in future posts starting with the next post on building the short truss wall on top of the earth contact north concrete wall.  The top of the concrete wall is decidedly unlevel so the challenge of standing a level wall on it without gaps between will be addressed.

Construction - Second Story South Wall

The previous post concerned the construction of a permanent and temporary second story floor on which to work on the second story walls and roof.  Here we are dealing with the 10+ foot south window wall for the second story, the top of which is a little over 20 feet above the first story floor.

Change in Window Configuration

Click on the drawing

Originally I planned to use seven double-window sets as clerestories in the south wall, as shown in the drawing. When I laid out side-by-side the seven pre-made window sections containing two windows each, they clearly were too crowded. Consequently, I reduced the number to five double-sections, stood them up and viewed them from the street. The proportions were definitely better.  Then it made sense to add back a couple of single windows as a way of softening the monotony of the facade and to stay in compliance with the minimum code requirement of 4% glass-to-floor area.  So I dismantled the two extra sections and reused the components to make wall sections for single windows that will have the same 3' x 5' dimensions as the individual windows in the double sets.

Adding Height to the South Wall

An end of the truss jig was cordoned off with
 2 x 4s for making 24" x 15" inserts; the plywood,
  nailed to a 2 x 4 frame, serves as a gusset 

The plans call for 12" thick cathedral ceiling for the first story shed roof that extends southward from the second floor wall.  Accordingly, the height of the wall was designed to be high enough to accomodate windows above the roof that will be pitched at 12/2.5. However, I will be using ceilings that are +/-20" thick. If the wall height isn't increased by at least 8", the pitch of the roof would have to be lowered to keep the roof from overlapping the bottom of the windows.  This is not an option because a slope of less than 12/2.5 is not recommended for metal roofing. The pre-made window sections that will comprise most of the wall were designed for an 8' wall and will therefore have to be heightened by a total of 24"  -- 16" to satisfy the original drawing plus another 8" to accomodate the thicker roof. Unfortunately, the additional 8" will place the sills above the 44" maximum height for egress windows but, fortunately, only the single window in the bedroom at the east end of the house will be affected.  For it to meet code, there will have to be a permanent riser below it on which an occupant could stand while exiting in an emergency.

I temporarily modified the jig that I used for wall trusses to make 24" high inserts to go between the window sections and the floor.  Admittedly, the inserts looked a little goofy but, when tied in with bolts, nails and strapping, they did the job.  

Raising the Wall

The four wall sections before raising; the section with the saw
laying on it and without its top and bottom plates is to be
raised last (click on the photos to enlarge them for more detail)

The window sections comprised most of the second story south wall but a couple of wall trusses were needed at both ends of the wall to connect later with the east and west rake walls. As soon as the extra trusses were ready, I cut the four 2 x 6 top and bottom plates to length, laid them side-by-side and marked them for attaching to the wall sections and the new trusses.  Then it was a matter of nailing them to the trusses and wall sections while keeping the outer edges of the tandem 2 x 6s exactly 15" apart, the same as the wall components.  I divided the 58' wall into four units in order to keep the weight within reason for raising.  I left the top and bottom plates off of the shortest unit since it would be the last to be raised and might need narrowing in order to fit into the space between the adjacent units that were already up.

Unsuccessful attempt at using wall jacks

Step-son, Keith, helped raise the walls. We assumed that the sections would be too heavy for raising without wall jacks but, after we were half through with using them for the first unit, we realized that they were not properly adjusted for a 10' wall and had to lower the wall back to the floor.  Instead of adjusting the jacks, we removed them, under the assumption that we had under-estimated our ability to raise the wall without them. So, in order to keep the wall from sliding over the edge of the floor, we used rope to tie the bottom and the top of the wall to the existing wall to the north.  Then two of us raised the first unit surprisingly effortlessly and continued to do so for the other three units.

As soon as the first three units were upright and the bottom plates were temporarily fastened to the floor with duplex nails and the top plates fastened together with clamps, we could dry-fit the unattached 2 x 6 plates for the last unit then attach them to the unit.  When we raised the unit, it fit nicely between the two adjacent units.

Aligning and Securing the Wall
As the units were raised they were stabilized with braces between the wall and the floor.

Second story wall housing a total of twelve 3' x 5' windows

Fortunately, the raised wall was perfectly plumb in an east-west direction, which was to be expected because the individual window units were shop-made in a jig. And each of the four wall units was checked for square while still laying on the floor before nailing on the top and bottom plates. All that remained was to get the wall (a) straight at both the top and bottom, (b) level on top and (c) plumb in a north-south direction. The braces were attached to the wall with drywall screws so the screws could be backed out and refastened as the wall was tweaked.  The duplex (double-headed) nails between the bottom plates and the floor provided the same flexibility.

The wall from a different perspective; notice the nailers
bridging the window openings for safety reasons; the
 height is just over ten feet; the window sills are slightly
too high to meet code for egress

We started the alignment by straightening the bottom and the top using taut mason's lines while loosening and refastening the tops of the braces and the duplex nails as needed. The clamps sufficed for the top temporarily.  As with conventional 2 x 4 or 2 x 6 walls, we used a double top plate, i.e., a second layer of 2 x 6's stacked on top of the ones that were nailed to the wall sections before raising the wall.  We installed the ones on the interior side of the wall first and used them to pull the wall perfectly straight and hold it straight, assisted by a mason's line.  Of course, as is standard practice, we staggered the locations of the ends of the boards relative to the first tier of top plates so as to stiffen the wall.

The floor under the wall was not perfectly level so the top of the wall also was not perfectly level, primarily in one area.  In order to correct the problem, we used shims under the bottom plates to level to a mason's line the top of the wall.

All that remained now for proper alignment was to plumb the wall in a north-south direction and secure it definitively to the floor.  For plumbing, we used shims under the bottom plates as necessary while loosening and reattaching the braces.  Then we used 6" construction screws and nails to fasten the bottom of the wall to the floor joists and band-joists.  

Our location places us at risk for two catastrophes.  Two hundred feet below us is an abandoned coal mine and subsidence is not uncommon in ours and the surrounding counties.  Also the New Madrid fault in southeast Missouri near its border with Tennessee has a 25 - 40% chance of a magnitude 6 earthquake within 50 years and a 7 - 10% chance of a 7.7 magnitude.  Either would cause serious damage in the St Louis region. Consequently, the final job to secure the wall was heavy hurricane strapping to tie it to the lower floor framing and to the major beam under the catwalk.

Installing Cripples
The purpose of cripple studs under the window openings is mostly for fastening sheathing

Cripples anchored at the bottom by 2 x 4s

and drywall but a secondary function is to support the sills under the windows which, in turn, supports the window. The latter function is more important for conventional 2 x 4 or 2 x 6 walls whereby windows are supported usually by one 2 x 4 or 2 x 6 installed flatways.  With our truss walls, each window is supported by two 2 x 6 sills installed on edge thereby making the secondary role of the cripples largely moot.  

I spent a few minutes making a temporary jig in which to nail the double cripples to a short 2 x 4s before nailing them in place.  I opted for the 2 x 4s cross-ways of the bottom plates rather than toenailing the cripples directly to the plates to make the cripples easier

Quickey jig for nailing cripples to 2 x 4s

to install and for more secure fastening at the bottoms. The tops were notched around the sills so they were well-nailed on top.  I might have opted for toenailing if the bottom of the wall was to be exposed to the exterior in order to avoid thermal bridging by the 2 x 4s. But not to worry, the bottom of the wall will serve as the top part of the wall for the first story and the bottom third of the cripples will receive drywall instead of sheathing.

All exterior walls for the house are designed for trusses 24"oc due to their stiffness. The cripples, however, are 16"oc just like the typical 2 x 4 wall framing of most houses.