I am often asked how many bales will be needed in my client’s straw bale houses. I too have to know the answer to this on all of my own projects. There are a number of ways to calculate the bale requirements. Click the following link (www.strawbale.com/articles/straw_bales_house.html) to see an article I just wrote for www.strawbale.com on the three most commonly used ways to calculate bale quantities for your straw bale house. My preferred method, the second of the three listed, is given here.

Calculate the number based on square footage of the wall surface area

One way to estimate your bale needs is to go a bit more in depth and calculate the number based on square footage of the wall surface area. In other words, you calculate the total lineal feet of straw bale wall and then multiply that by the height of the walls. This yields the square footage of wall surface. For a gable roof, measure one half the width of the building at the gable and multiply it by the total height of the gable end. That will give you the square footage of the entire gable as if you took the two triangles and glued them back together in the shape of a square at each gable end.

You can then remove the square footage of window and door openings from this number. Once you have all of the openings removed, divide the total square footage by the square footage of your bales. For this, consider a 14″ tall by 36″ long bale would have 504 square inches or 3.5 square feet of bale surface area. This will give you the exact number of bales you will need to build the structure.

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My fiance wants to have a crawl space under the house for the plumbing and the heated floor system so he can get to the pipes easier if they should bust or something. He wants the space to be at least 18″. What do you suggest.

Machelle,
The exact dimension for the roof overhang actually depends on the area in which you live. The latitude of your area determines the angle of the sun in all seasons and thus is used to calculate exact sizes that will block the sun in the summer while allowing it in in the winter. That is something your local power company may be able to tell you, i.e. the angle of the sun in your area. If not, you can go on line and look into simple sun charts like the one at the following link: http://www.esru.strath.ac.uk/Courseware/Design_tools/Sun_chart/sun-chart.htm. They can be a bit difficult to use if you are not accustomed to them, so it is best to try and find the local information first. I typically use an overhang of 2-3 feet depending on the design. It is also a good idea to use an overhang for the first floor even if there is a second floor above it. In other words, be sure to have two roof systems or a deck that will protect an otherwise large expanse of wall.
In terms of the floor framing, you can build a bale house on a standard crawlspace floor system as long as the size and spacing of the floor joists accounts for the extra load of the bales (about 40 pounds per square inch additional dead load).

Hello,
My husband and I are thinking of building a straw bale house in the mountains and I wanted to know if you could build on a pier foundation. Thank you for all the information.

Hi Gigi. You can indeed build on a pier foundation. There may be some engineering involved to make sure all your loads are properly distributed, but it is certainly an option for you.

At 4:56 PM, Machelle said…

My fiance wants to have a crawl space under the house for the plumbing and the heated floor system so he can get to the pipes easier if they should bust or something. He wants the space to be at least 18″. What do you suggest.

Machelle Bice

Maud, Ok

At 4:58 PM, Machelle said…

How far out should you place roof overhangs on a haybale home to make it passive solar, and what type of extra supports do you think we would need.

Machelle Bice

Maud, Ok

At 2:12 PM, Andrew Morrison said…

Machelle,

The exact dimension for the roof overhang actually depends on the area in which you live. The latitude of your area determines the angle of the sun in all seasons and thus is used to calculate exact sizes that will block the sun in the summer while allowing it in in the winter. That is something your local power company may be able to tell you, i.e. the angle of the sun in your area. If not, you can go on line and look into simple sun charts like the one at the following link: http://www.esru.strath.ac.uk/Courseware/Design_tools/Sun_chart/sun-chart.htm. They can be a bit difficult to use if you are not accustomed to them, so it is best to try and find the local information first. I typically use an overhang of 2-3 feet depending on the design. It is also a good idea to use an overhang for the first floor even if there is a second floor above it. In other words, be sure to have two roof systems or a deck that will protect an otherwise large expanse of wall.

In terms of the floor framing, you can build a bale house on a standard crawlspace floor system as long as the size and spacing of the floor joists accounts for the extra load of the bales (about 40 pounds per square inch additional dead load).

Andrew

I want to estimate the vertical load on a residential building load bearing straw bale wall but doesn’t know how to go about,

That is something for an engineer to tackle. Those types of calculations are outside of my reach.

Hello,

My husband and I are thinking of building a straw bale house in the mountains and I wanted to know if you could build on a pier foundation. Thank you for all the information.

Hi Gigi. You can indeed build on a pier foundation. There may be some engineering involved to make sure all your loads are properly distributed, but it is certainly an option for you.