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Archive for April, 2010

Roundwood Braces

Roundwood Braces

One way to save money and reduce your impact on the environment is to use unmilled roundwood when building your home. Wood in the round is much stronger than standard dimension lumber and requires less processing. In our case it enables us to use local, sustainably grown wood instead of wood shipped hundreds of miles. Plus, because we’re using eucalyptus wood our roundwood is fairly durable and insect resistant. Using roundwood does take a bit of extra work, but I feel the benefits make it well worthwhile.

We use roundwood for many purposes, including corner braces to keep window and door bucks square, braces to prevent bowing of frames, long poles to keep window and door bucks plumb, stakes and even nailers for attaching electrical junction boxes, shelving, etc.

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Sheet Metal Anchors for Rough Frames

Sheet Metal Anchors for Rough Frames

It seems most people are using wood to attach rough frames (“bucks”) for windows and doors to earthbags. We have termites in our area and so we’re using galvanized sheet metal for this purpose. I’ve used both kinds and discovered sheet metal anchors are much faster to make.

The first step is to cut sheet metal into 7”x12” rectangles with tin snips. (We paid a little extra to have them pre-cut.) Then score a line 2” from one end with a large nail and straight edge. (We used a 16d nail and a piece of sheet metal.) Score the metal about three times and then bend it along the line into a right angle with your hand. Pound in some nails from the bottom side, place the anchor in position and then add nails into the earthbags (galvanized roofing nails work best), and deck screws into the wood. Place anchors on both sides of frames about every four courses of bags.

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The Dometown Project

The Dometown Project

I’ve been corresponding with Richard Laurens who is developing a geodesic dome design that rests on earthbags and is covered in earthbags. His original plan was to use rammed tires to support the domes, but now he’s convinced earthbags are more practical. I’m encouraging him to use scoria-filled bags since he plans to build his designs out west near a source of scoria.

I’ll let Richard describe his project in his own words.

The Dometown project is a name I gave to my plan for a small cluster of dome shaped homes. I would start with one, and keep on building them. The center clear parts are greenhouses.

Buckminster Fuller’s original idea was a home that could be built anywhere for cheap; why not expand that idea into a “life pod” that can recycle water and grow its own food? The basic premise is this: We have a water source, an “eternal” power source (wind, water, or solar), and very contemporary and comfortable self-sustaining dome home. It’s just a very simple solution, and expandable.

The geodesic, or monolithic dome structure is not only appealing to the eye, it is efficient and cheap to build. The dome numbers and designs are nearly limitless, and four simple domes with a fifth dome in the center would make an excellent home with about 2500 square feet of space. That is a good sized home! I estimate working by hand with minimal tools. I can make this house in about a year for around $20,000.

The dome is a 4th degree electrical conduit pipe dome, bolted at the vertexes and welded. I then cover the dome with wire mesh and stack the bags on the outside. The windows are standard ones, placed into a ‘work horse’ type of sconce.

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Structural Mesh

Structural Mesh

Wrapping walls in mesh – starting under the first course of bags and going over the top of the bond beam – is a simple way to add a great deal of extra strength to your earthbag structure.

Fishing net and plastic lath are ideal for wet climates. Galvanized wire lath or chicken wire is suitable for most situations.

Overlap mesh at least 12” (30cm) and keep seams at least 24” (60cm) from corners.

Lay 24” (60cm) pieces of strong twine or cord across the bags every three or four courses and every 24” (60cm) horizontally along the wall. Use this to firmly tie mesh on both sides of wall together.

Drawing credit to Patti Stouter.

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It’s not difficult estimating costs for small houses. Simply add up the number of each main component and multiply times a realistic cost. Then add about 5%-10% extra to cover unforeseen expenses. Use current, local prices for most accurate results.

Here’s one article that explains how to estimate the number of bags you’ll need.

You can also do a per square foot cost estimate. This method is not as accurate as a detailed cost breakdown, but does provide a rough estimate.

Here’s one example using dirt cheap building techniques. $10/sq. foot is about as low as you can get using simple, low cost materials and methods (earthbags, rubble trench, earth plaster, locally harvested wood, recycled materials, etc.). So a house of about 300 square feet would cost around $3,000 not including land or labor. (300 x $10 = $3,000) Then add any extras you may want: radiant heat, better windows, tile counters, etc. to get a more accurate cost. The cost will be significantly higher if building in areas where you have to meet building codes. Seek out remote, rural areas with few or no building codes to minimize costs.

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I got a fortuitous email from the sales manager of a large factory in China that manufactures polypropylene bags wanting my business. During the course of our email exchanges I was able to find out what they can offer by way of bags, costs and transportation.

The China Forest Packaging Group in Qingdao, China can provide a wide range of polypropylene bags, both as individually sewn bags, and as long tubes on rolls. They ship via containers and can send these all over the world…including Haiti.

Standard 18″ X 30″ bags run about $0.11US each and the longer 18″ X 34″ bags are about $0.12 each. The same bags with UV stabilization are about a penny more. These prices are FOB Qingdao. The cost of shipping a 40′ container to the East coast of the US runs about $3,200US and this can hold about 330,000 bags….so this would add about a penny per bag.

The long tubing in rolls are 3500 meters (11,150′ or 2.2 miles) long. This is the equivalence of about 3,700 standard bags. The cost of each roll is about $482US, so that would mean that the equivalent price compared to individual bags is about $0.13US…so there is no saving in buying the long rolls.

They can supply gussetted bags by special order, and it would be necessary to give them exact specifications for this.

They need up to 30 days lead time to fill orders.

For more information you can contact Bill Chen, the Sales Manager. (He does communicate in English). chinaforestpackATgmail.com   Tel: +86 151 656 64026  Fax:+86 536 827 3455

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My previous post described an alternative bond beam for curved walls; this post is on straight walls. Conventional reinforced concrete bond beams may not be affordable or the materials unavailable. Or maybe you want to reduce or avoid using cement. Here’s one low-tech, low-cost bond beam design. It’s even possible to use salvaged materials for all or most of this bond beam.

Alternative Bond Beams for Straight Walls

Alternative Bond Beams for Straight Walls

Materials: Corrugated metal roofing, 2×4 (5x10cm) wood, metal brackets/mending plates and screws, 16d nails, ½” rebar, and twine, rope or strapping.

In this design, corrugated metal and wood top plates are bound together with twine or strapping to stiffen tops of walls. Top plates, joined with metal plates, provide for easy attachment of trusses or rafters. Drill holes in top plates every 24” (60cm) for rebar pins.

Vertical rebar pins about 24” (60cm) long tie the bond beam into the wall below. Driving the rebar at alternating angles adds strength.

Use 8-12” (20-30cm) wide pieces of corrugated metal roofing overlapped at ends about 12” (30 cm) and nailed to the bag below at overlap points. Lay two courses of earth-filled bags above the corrugated metal strips.

Drawing credit to Patti Stouter.

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