Building a straw bale house on top of a concrete slab is certainly the most common system employed; however, it’s not the only way to go. If you have reason to build a raised floor system, you can. In the photo to the left, you’ll notice the change in grade from one side of the picture to the other. That’s a great reason not to build a slab as the amount of either back fill or concrete would be insane to make it work as a flat slab. There are a lot of advantages and disadvantages to each type of construction, as with anything in life, so let’s take a look at some of those now to help you decide what is best for your build. (Remember, there are lots of other options too from earthen floors to pole structures. Don’t get stuck in the belief that you have limited choices. The largest limitation will likely be the building department, not the fact that you’re using bales for your walls.
Rather than focus on the negative and talk about disadvantages, I’ll simply discuss the advantages of each. Let’s lay it out here.
Concrete Slab Advantages:
1. Large amounts of thermal mass. The ability to use that mass for passive heating and cooling is large.
2. Radiant heating. Again, the mass comes into play. Radiant tubing installed directly in the floors is an extremely efficient way to heat a house.
3. Durable. Nothing is more durable than hard concrete over time. It just gets harder with age.
4. Ease of installation. Built all over the world, concrete slabs are installed by many tradespeople. This brings down the cost as well.
5. Back to cost. Because the slab acts as the structural element of the floor AND the finished floor, it is a relatively low cost option.
Wood Floor Advantages:
1. Perfect for working with uneven terrain. Like the photo at the top of the article, a raised floor can accommodate a sloping lot.
2. Deep excavations requiring basement walls lend themselves well to framed floors. Why not use a daylight basement or a full basement?
3. Applying wood, bamboo, cork, natural wool carpet, or any other finish flooring type is easy, and in many cases, easier than with concrete.
4. Comfort under foot. Wood floors have built-in, limited deflection which allows the floor to “give” under foot. This makes it very comfortable to walk on.
5. Access to utilities. Raised wood floors allow you to maintain access to things like plumbing waste lines which would be buried in a concrete slab. Should they ever fail, you have easy access for repairs.
There are some differences with the installation of bales over a wood floor as compared to a concrete slab. In most case, working over a wood floor is easier in terms of the bale installation; however, you need to decide what advantages are important to you and also what disadvantages come along with them. In my soon to be released, new production I show the details of working over a wood floor where as my old production focused on installations over slab construction.