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Posts Tagged ‘wind resistant’



These homes are looking better and better. The second video shows the construction of 11 SafeT homes in a Haitian village that were built in just one week. In addition to the advantages mentioned in our previous blog post about these Grain Bin Homes, the homes are engineered, include screened soffit vents and a central roof opening, solid steel door, gutters for roofwater collection, window screens and lockable window shutters to resist strong winds up to 150 mph. And, as pointed out previously, the steel is over 95% recycled content and can be recycled at the end of it’s 70 year life span.

Update: Update: Sukup Grain Bins Earn 5,000 lb. Load Rating (it can hold a car on top, making them the strongest in the industry)

Sukup Grain Bins Earn 5,000 lb. Load Rating

Sukup Grain Bins Earn 5,000 lb. Load Rating

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Cylindrical Earthbag Shelters

Cylindrical Earthbag Shelters

Here’s a great shelter design by Delani that was posted at Core 77 as part of a recent shelter competition.

Sometimes the best ideas are the simplest, and this design is exquisite because of its simplicity. That means it’s inexpensive and easy to build. And no doubt about it, it will work structurally. (However, it remains to be seen if these shelters would be culturally accepted.)

Here’s the description from the Core 77 website:
Kay 0.2 (Kay means house in kreyol) is a rapidly deployable, easy to build shelter that can protect occupants from a cat 5 hurricane. Construction specs: sandbags are stacked in a circular shape to form a cylinder with inside diameter of 8 feet with a height of 10 feet. A roof of corrugated steel placed atop the wall at 8 feet height then 2 feet of sandbags are added on with a scupper to catch rain into 55 gallon drums in back.

Comments: I would slightly taper one course of bags just below the metal roofing so water will drain freely toward the rain barrels. Add rafters perpendicular to metal roofing. (No purlins necessary.) Windows and other design features could be added as desired. Tip of the hat to Delani for this exceptional design.

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Roofing hold-downs resist uplift

Roofing hold-downs resist uplift

Here’s a simple way to help prevent metal roofing from being blown away. Roofs are typically quite vulnerable to uplift in windy areas. There are commercially available roof hold-downs that bolt trusses and rafters to walls, but I’ve never seen the system described here. It was inspired by hearing all the stories about metal roofing blowing off in Haiti. (Apparently it’s routine to reattach metal roofing after major wind storms.)

This hold-down system is low cost and simple. It consists of 1/4″ x 3/4” flat galvanized steel bars bolted to purlins. Drill bolt holes at the top of corrugations. Use rubber washers to prevent roof leaks. (Insert rubber washers below the bars.) The drawing shows hold-downs located at the top, bottom and middle of each 8’ long sheet of roofing. Adjust the spacing between hold-downs for your region. The higher the wind speeds, the closer the spacing.

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Domes are very strong and perhaps the best option for many areas. However, in rainy climates they are prone to leaks. (Domes originated in desert regions, after all.) In high rainfall areas, roofs with overhangs to protect walls are recommended. Roofs need to be very well built with hurricane tie downs. This is the weakest link in the design because roofs are vulnerable to wind damage, so study up on the specialized building techniques available.

Consider something like this Sand Castle house built by Steve Kemble and Carol Escott. Round, hexagonal or octagonal shapes are all good choices because wind will flow around the building. Same idea applies to the roof.

One big consideration is building on grade versus building on piers off the ground. Try to find some high ground and build on grade (or 1’-2’ above), since this will be stronger and less expensive.

Bag fill: The crushed coral/sand mix used on the Sand Castle is a good choice if available locally. Road base is more commonly available and can be stabilized with lime. Road base is the clay/gravel mixture used to build roads. It’s cheap, plentiful and very strong. And with lime added, walls become virtually waterproof and almost as hard as concrete.

One story structures reduce exposure. Design in fast mounting storm resistant window shutters. Keep roof overhangs to a minimum, maybe 24″, to help prevent uplift.

So in summary, a properly designed earthbag structure is the strongest sustainable building system that I know of. The only thing stronger is reinforced concrete, and that’s not sustainable.

I have numerous plans that could be adapted for hurricane and tornado prone regions at Earthbag House Plans.

These plans are available through Dream Green Homes. I modify plans at no extra cost to meet your codes.

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