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Straw Bale Building: DIY Wrap-Around Porch

7/9/2011 1:57:54 PM

Tags: DIY porch, wrap-around porch, straw bale house, straw bale home, adobe plaster, vigas, felt roofing paper, tar paper, rafters, Dave Larson

Dave L HeadshotClimate and weather in the high desert of Arizona are harsh. Granted, we don’t have the severe cold of northern states, but monsoonal rains driven by 50 mph winds and intense sun that will burn skin through a long sleeved shirt can be tough on a building made of straw and adobe clay.

To counter the effects of the wind, we built our house with its back to the prevailing winds from the west and put only one window in the back wall. For rain and sun, we opted for a 360 degree porch or patio. Choose the name you like. Basically it’s an extension of our roof 8’ past the outer wall and floored with flagstone. With this overhang, our adobe plaster walls were protected from all but the most severe driving rains and our windows were shaded from the intense Arizona sun. The overhang also gave us a shady spot out of the wind to enjoy our mountain views any time of day. All good things!

 Porch Framing Start 

Our porch began once the trusses were installed on the house. We completed the sides of the porch completely before starting on the main house roof to allow access under what was to be a shallow, 12 inch overhang from house to porch as well as making work on the main roof accessible without ladders.

 Porch Post Anchors 

We had dug out and poured 12”x12” blocks of concrete with 6” post anchors to accommodate our porch posts when we poured our footings. Out here, peeled logs called vigas are often used as visible supports in roofs and ceilings. We used them as vertical porch posts for Southwest aesthetics and the price was not too bad.

 Porch Beam Corners 

With the vigas plumbed and braced, we fastened the bases firmly in place with lag screws. Eight foot 4”x6” beams spanned the distance between the tops of the vigas. To attach them to the uprights, long barn spikes were driven in at an angle through predrilled holes. We used a lap joint cut into the beams at the corners and secured them with a spike driven through the lap joint into the top of the viga.  After the beams were set, 3" garden post stock was cut into 2' lengths with opposing 45 degree cuts and used as a corner brace for the top of the viga. We liked the way it looked and felt it was another move toward stronger building.

     T Strap Fasteners 

In honor of my blacksmith grandfather who believed that it was impossible to build something that was too strong, we used steel t-straps to further strengthen the joints between beam and post.

With the outer “wall” of our porch in place, we measured and mounted angled rafter/joist hangers from the bond beam plate. Angles cut with our trusty chop saw made a good fit for the rafter ends against the bond beam. Recognizing that wood twists and warps and that sometimes we aren’t as accurate as might be, we left the outer ends of the rafters to be cut in position with a handsaw after a chalk line marked our target. This enabled us to have a straight fascia board.

 Rafters with Hurricane Straps 

After ensuring the 2”x6” rafters were true and square, we fastened them to the bond beam with hurricane straps. A little more time spent with some accurate marking and cutting a series of double miters produced our corner hips. I found that double miter cuts on an inexpensive chop saw such as we have is a bit time consuming. One of those places where someone who is not a pro carpenter learns to measure twice and cut once. Crossing your fingers doesn’t hurt either, but not while you’re cutting

 Sheathing on a hip corner 

Before nailing on the fascia boards, a chalk line and adjustable square gave us our cut lines and we sawed off the ends of the rafters parallel to the bond beam.  Some heavy lifting brought the OSB sheathing up on the rafters, followed by a few snaps of the old chalk line and the nail gun fastened the sub-roof to the porch. Our first shade! When the OSB was in place, cut long to allow for the depth of the fascia, we began nailing the 1”x6” fascia boards into place.

 Steel Roofing on the Porch 

Rolling out tar paper or felt roofing paper, call it as you like, in a high wind is not my idea of a great time. As a consequence, we began our roofing early in the morning, before the daily winds and used some lathing and short sheet rock screws to keep our paper in place in the event of a stray gust. We only did the porch sides and left the corners and gable ends for after main roof was completed. We wanted to be able to build from the porch roof without damaging the finish on the roof steel, but had to put steel on before hand to accommodate the roof overhand. A matter of planning and staging.

 Set to predrill steel roofing 

So, leaving the ends unpapered for now, we attached our drip edge above the felt paper and made ready for the steel porch roofing. Each manufacturer and each roof rib design calls for a slightly different screwing pattern. When we received our steel, a cover piece was included to protect the finish on the purchased pieces. We set up saw horses under our newly made shade and made a template from the cover piece following the pattern recommended. Carefully predrilling holes in the template meant that we could drill a pattern of starter holes in each sheet of roofing steel on the ground.

Being able to start gasketed roofing screws in predrilled holes meant that there was consistent fastening and less bending over.  As you can see from the pictures, this is a desirable thing for me, enjoying an excess of both years and girth. The uniform screw pattern made for better roof aesthetics as well.

The ground crew, Barbara and Anneke, attached strips of mastic or roofing "bubble gum" on the appropriate edge and sent up the predrilled sheets. The side roofs were covered with steel in about an hour. We had a porch and were ready for the main house. After that, the remaining paper, drip edge, and steel was installed to complete our project.

While we have more square feet under roof on our porch than on our house, with attendant costs and work, I would not build differently.  I can wander outside to view our beautiful desert and be dry while watching the rain fall on our often parched desert or relax in the shade while sheltered from wind.  I am thankful we decided to build a wrap-around porch for our straw bale home.



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