Timber frame straw bale house plans

The classic timber frame, with its large-dimension lumber and carefully crafted joinery, is very beautiful. Timber-framed buildings have an elegance and solidity that is impossible to duplicate, and its recollections of the craftsmanship of the past have brought the style a recent resurgence in popularity.

If you are building for the first time or have never tried timber framing, you must recognize that it requires a good deal of skill and practice. It is entirely possible to learn these skills, but do not expect to erect your building quickly as a first-timer. If you decide to hire out, there are many experienced timber framers with a variety of styles. They can do beautiful work in a reasonable length of time, but timber-framing can be expensive.

Timber-framing occupies an unusual place in many building codes. Recognizing its historical validity, many building officials will allow its use without requiring an engineer's approval, especially when an experienced framer is responsible for the design and/or construction.

Advantages: beautiful, strong, long-lasting, satisfying to build Disadvantages: costly, large timbers often not sustainably harvested, steep learning curve for beginners, complications integrating bales.

Mechanically connected post and beam Mechanically connected post and beam techniques and materials can substitute for the notched joinery used in timber-framing. A variety of mechanical fasteners can be bought or fabricated to attach posts and beams together. Commercial brackets and fasteners are generally accepted by building officials; homemade versions may require special approval. Carefully assess your choice of connectors if you are exploring this option; often they are expensive, and it is not difficult to end up spending as much money on mechanical fasteners as you might do on hiring a timber-framer.

Post and beam systems often eschew the large-dimension lumber used in timber-framing in favor of site-made or commercially available laminates. To create an onsite laminate, a number of pieces of standard dimension lumber are joined together using a certain nailing or bolting pattern. These laminate posts and beams may be suitable for your project and accepted by your building official, and often cost less than a comparable solid timber.

Commercially available laminates are also an option. They are made from glued strands of wood and are designed to equal the load-bearing capacity of large-dimension lumber. Their cost is often reasonable, especially if you must otherwise import solid timber from a great distance. Some environmentalists praise commercial laminates because they are made from waste wood and therefore save large trees;others are less positive because of the nature of the glues used to create the laminates. If the chemical composition of the glues concerns you, be sure to do some research before inviting them into your home. Commercial laminates are often available complete with appropriate fasteners and joinery from lumber supply yards.

Manufactured joists are also an option for creating beams. These joists use oriented strand board (OSB) — a product similar to plywood — sandwiched between lengths of small dimension lumber to create strong I-beams. They can be ordered to meet your length and strength requirements, and use fewer glues overall than do full-sized laminates. They are also much lighter to carry and lift into place.

Advantages: building code friendly, relatively simple to construct, can choose more sustainable lumber options Disadvantages: can be costly, complications integrating bales, can use a lot of lumber

Modified Post and Beam

Modified post and beam designs can blend the lumber-saving elements of load-bearing designs with the structural advantages of post and beam. This style uses a structural top plate, similar to that used for a load-bearing structure, as a continuous beam and transforms the window and door bucks used in load-bearing buildings into structural posts. Since a regular post and beam design would use similarly strong window and door bucks, lumber savings can be significant. The posts are rigid box beams constructed of small dimension lumber — usually 2-by-4s — and plywood or OSB, which means that only small reforested trees need to be harvested. The 2-by-4 and plywood supports can be stuffed with straw

to provide nearly identical insulation values to the rest of the wall. Simple to construct and relatively miserly in lumber usage, this option allows for a post and beam framework that can be completely buried in the straw wall without any need to notch or cut bales. You save time and space. Until such designs become common, how-ever,it may take an architect's or engineer's stamp for a modified post and beam design to get permit approval.

8.5: A traditional timber frame (in this case using recycled timbers) can be erected as a stand-alone structure, then wrapped or in filled with straw bales.

8.6a - c: These thin posts are used to frame door and window openings and corners, creating a lightweight frame that is then infilled with bales. When the posts are as wide as the bales, no notching and cutting is required.

Advantages: simple, low lumber usage, easy integration with bales

Disadvantages: needs special engineering

Standard Stick Framing

It is relatively easy to use a conventionally framed stud wall system with straw bales. In this system, the bales would be stacked between the studs. Two-string bales can fit quite well into a standard 16-inch stud spacing if stood on their ends. Some additional framing will be required to compensate for the extra width of the bales, but this is easily accomplished at the design stage.

Advantages: simple, code accepted Disadvantages: high lumber use, difficulty integrating bales

Truss Systems

Full truss systems, wood or steel, are comprised of all-in-one wall and roof trusses,which are spaced at regular intervals. Bales can be placed between

8.6a - c: These thin posts are used to frame door and window openings and corners, creating a lightweight frame that is then infilled with bales. When the posts are as wide as the bales, no notching and cutting is required.

the trusses. Strapping is added between the trusses to help stabilize them, and plaster eventually gives the whole structure further stability.

Buildings of this sort can be erected very quickly, and because the trusses will be manufactured to the specifications of an in-house engineer, code approval should be relatively easy to obtain. The truss engineer will need to be aware of bale thickness and the odd spacing bales will require, but these dimensions shouldn't prove to be a problem. A truss system could be designed to allow bales to be used continuously from walls to ceiling, since truss spacing would be tailor-made for bales, anyway.

The cost of executing a truss design varies greatly, depending on the simplicity of the design. A relatively straightforward square or rectangular design will use identical trusses for the entire structure; a complicated design will require a series of varying-sized trusses that will up the cost significantly.

Advantages: simple, pre-engineered, easy bale integration, low cost Disadvantages: high lumber use, can't build your own trusses

Concrete

Concrete columns and concrete top plates can be used together or in combination with other materials. Stacked concrete blocks or poured concrete columns can support roof loads. Blocks are easily dry stacked, and the hollow cores can be filled with cement and rebar when the column is at full height. This option requires no form work and little experience. Poured columns require either homemade or prefabricated forms to contain the wet concrete. The simplest and cheapest forming system is the Sonno-Tube, but since it creates a round column, you'll have to figure out how to blend the finished column with the bales. In either case, it is important to use adequate rebar to support the column. Check your building code or ask an experienced professional for guidance.

While concrete columns may cost less than certain lumber options and may be easier to build if you are unfamiliar with woodwork, they do have two drawbacks. First, columns built to the inside of the straw walls remain visible in the house after the walls are erected. Forms that incorporate interesting patterns, pigment in the concrete mix, or a simple surface paint job could help solve the esthetic problem of exposed concrete. Second, columns that are buried in straw walls create a thermal bridge, allowing heat to transfer outside much more quickly and lessening the overall insulation value of the wall. Styrofoam or other rigid insulation can be used to reduce this effect.

A concrete top plate — for post and beam or load-bearing designs — can be formed on top of straw walls to replace the typical unit made of wood. Formed with lumber that remains in place to allow for the attachment of roof framing and stucco netting, this option could be cheaper and faster to construct than a wooden unit. A concrete top plate creates a good seal against the bales and produces a level upper surface. The pour will bond with the top layer of straw and fill in any uneven surfaces along your top row of bales. For load-bearing designs,wires or cables can easily be looped over the entire unit or routed through tubing embedded in the concrete.

Concrete beams are also an option. A concrete beam will add significantly to the dead loads your framework and/or straw walls will have to carry and reduces the allowable span between posts or the width of the openings in a load-bearing wall. Check with your building inspector before you commit to this option. At the finishing stage, concrete is easier to plaster over than wood. As with concrete posts, concrete beams create a thermal bridge at the top of your walls unless Styrofoam or another rigid insulation is used inside the wooden forms.

For both concrete top plates and beams, adequate rebar should be used to ensure that the concrete is well reinforced against the loads they will carry. Lightweight concrete is available and could be used to lessen dead loads on the walls.

Advantages: long lasting, moisture resistant

Disadvantages: high environmental impact, poor thermal performance

Metal Frames

Prefabricated metal buildings have been very successfully integrated with straw bale walls. Prefab metal building kits are widely available and the prices are extremely competitive, and usually the kits come pre-engineered for building code acceptance.

Site-built steel frames are also feasible. Metal columns and I-beams are widely used in industry and have been building code rated, giving you accurate load figures with which to work and specialized information from which to draw should you choose to build with metal. Metal components can be combined with wood and concrete in various ways — an advantage if, for example, you have found some inexpensive steel joists that could ride on wooden or concrete posts. It is quite possible to find used or surplus components at a reasonable cost that can be incorporated into your design. As with concrete, you must account for the minimal insulation value of metal and plan around the esthetic effects of exposed steel in your home.

A site-built metal frame will require that you have welding skills and specialized metal-working tools, or you will need to hire appropriate labor. Kit buildings often just need assembly with nuts and bolts.

Advantages: simple, cost effective, long lasting, pre-engineered Disadvantages: kits limited to basic rectangles, poor thermal performance, possible condensation issues in bale walls

Continue reading here: Hybrid Systems

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