Natural concrete alternatives

I am planning on building a small bungalow house in the future and I've started to look at natural alternative to concrete to building the basement foundation. So far all I have found doing some research online are greener concrete products by using recycled or byproducts to make concrete. The issue is they all still have concrete in them with a relatively high energy intensive process. The only thing I could come up with is using stones to make the foundation but that would still require some concrete assuming using stones would meet building code given the 7+ foot high foundation walls which will be a living space.

Does anyone know of any alternative or I am simply looking at a greener concrete product?

Thanks,
Kris

Hi Kris,

I understand you abhorrence for portland based concretes, anyone with a sense of place, and wanting a lower impact on it would have the same distaste. Unfortunately even the creation of lime mortars and natural concretes are energy intensive in their creation. Dry laid stone work can be used in many areas, but is very expensive to get done correctly, especially to pass the eye of an inspector or PE. Have you considered not having a basement at all and designing your architecture to penetrate the landscape less invasively?

Regards,

jay

I have thought of not having a basement but with a young family I need the space. I don't want to build a second story or expend out too wide to gain the same square footage. I may need to compromise and find the greenest concrete product out there. I was just hoping for an alternative.

Kris

Building up is cheaper than down these days. I wouldn't have a basement if I wasn't in tornado country, and if I had it to do over I would have built small root cellars and a tornado shelter instead.

I would do a timber-frame on piers with strawbale in-fill. Big square two story with open center and the kitchen woodstove in the middle--think old one-room schoolhouse sized to fit your family.

Jay's right, but sometimes you just have to bite the bullet and burn some limestone to make lime (adding CO2 emissions) so the building will be strong enough. Back in the time of the Romans, when concrete was "discovered" (developed?), it was a green technology because they used seashells and firewood to make lime. It still could be today if you found a cement plant that was using biomass to fuel their kiln.

Sometimes you can design the building so that you don't use a whole lot of lime, like using piers and having a crawl space instead of a monolithic pour foundation, but that doesn't sound like an option where you are. With your climate, you need a basement, and that basement needs to be strong enough to hold up the house, and it needs to go below the frost depth, so it sounds to me like you need to burn some calcium carbonate to make a good foundation.

Don't let the pursuit of having a smaller carbon footprint make you think that you are not allowed to make any footprints at all.

Hi Kris,

As a Designer and builder of Natural and Traditional architecture I would be remiss if I did not share my concerns with basements in general. They are an "architectural appendix" to the anatomy of building, stemming from the "root cellar," and what to do with it. Unless designed for a specific purpose, (weather shelter, root cellar, etc.) they have no place in good architecture. I have come to a point where I will turn down a clients contract if they insist on a 4 walled "pit" basement. (I will consider 3 wall walk outs in some cases.)

R Scotts observation is most accurate. You can build out or up much more effectively than down. This does not even begin to address the "pooling" effect that basements can have on indoor air pollution such as radon gas and other noxious "outgassed" pollution from building products.

I would also tend to agree with J. Elliott's observation about your carbon footprint. Note there are still manufactures of "natural concrete" though, like lime, are more expensive than "big industry" (big polluter) portland cement companies.

As a plumber and elctrician, I would not want to do without a basement.
No crawl space , attic, or slab can give you the same kind of access for repair, maintenance, and rehab.
Think of it as an engine room for your house.
Now, a walk in is even better, and some kind of outside access is almost a must.

I don't want to belabor William's argument for a basement, and as I said earlier, a walk our (3 wall) grade floor basement can be a very positive thing, as it is more ground floor living space than a true basement. William is also correct in the fact that any form of architecture needs an "engine room" as he put it. The proper term architecturally and in its design is called MEP (Mechanical, Electrical, Plumbing) spaces and/or hub which also supports the HVAC for the structure.

Where I must strongly disagree with William, is as a designer, the "basement" was an afterthought to stick MEP, not a planned intention, and is a very poor choice for stick MEP in general. In more advanced architectural design, which has been in Europe since about 1955 to 1965 is the concept of "disentanglement." Here in North America we often seen the MEP in a structure not working in complete concert with each element of design. Instead it is hidden behind walls, ceilings (of basements) and tucked into every "nook and cranny" that they can get stuck into. This is not the Plumber, Electrician or other mechanical contractors issue, but the designers. It is often an afterthought, and not a focal point of planned intention, at least not as you would see it most industrial or public architecture. In structures like this, even in this country, disentanglement has taken a very strong hold, and MEP is an initial element of design. That is why in these structures MEP contractors have there own space planned for them called "chase" or "trays" often inside walls, but with very easy access. The minimum wall thickness in our architecture is 250 mm (10") and goes up to often over 600 mm (24".) This might be throughout the architecture or just planned for in key locations to address William's concerns for the MEP and ease of servicing and facilitation.

Whatever the case, don't relegate MEP to the sub floor just because that is what you think everyone else is doing, they aren't. Make sure in whatever design you come to facilitate that the MEP are distinctly address and planned for. Disentangled architecture is not only easier to plumb and wire; it is extremely easy to update and facilitate change to any of the MEP elements. I would also make note that the majority of the architecture of the world, both modern and vintage does not have a basement as we know it here in America.

Thanks for all the great replies. The reason why I don't want to build a two story house is I plan on retiring there and stairs are not a great when you 65+ year old. Maybe a loft as a guest bedroom could be an option depending on the pitch of the roof line since I will be doing a green roof. The other reason is for not wanting to build up or too wide to obtain the same square footage is I want the house to blend in the environment. One option I may explore is only having to dig down part way and use the excavated dirt to backfill against the remaining foundation protruding (as see by my lovely drawing below).

I do admit the appeal of not having a basement come building time since I will be doing the majority of the work myself. I will continue to look at various concrete options and also explore basementless design.

Thanks,
Kris

Do you have a precast concrete panel supplier in your area? They use concrete extremely efficiently and offer many other advantages as well.

Kris Minto wrote:The reason why I don't want to build a two story house is I plan on retiring there and stairs are not a great when you 65+ year old.

Is there a difference between walking up and down a flight of stairs to the 2nd floor and walking up and down a flight of stairs to the basement?

I have questioned my ideas on building a basement myself and then decided to go with a walk-out but now perhaps no basement at all. I am wondering if there's truly enough benefits to filling in three sides of the house with dirt, considering the cost and additional preparations one must make for insulation and water/moisture infiltration.

Along the same vein of the OP, I'm also wondering if it's possible to to make the slab out of limecrete or even aerated limecrete. I understand that while lime requires energy to produce, it has much less of a negative impact compared to cement.

GREEN CONCRETE
Looking to the future, there is currently a greener form of concrete that traps CO2. Carboncure.com has a map of distributors that sells concrete which permanently sequesters CO2 gas - maybe if you are thinking of pouring a slab, check carboncure.com to see if you can order this greener version of concrete in your area. The cost of adding CO2 to concrete is offset by the added strength of mineralized CO2, so less cement is used in the concrete. The savings from using less cement (most expensive component of concrete) should keep you from paying more for this CO2 infused concrete. Here is a video from CNN that describes the impact of concrete in relation to our environment and explains how concrete can be used to sequester CO2 and actually offset the greenhouse gases produced in manufacturing cement: https://money.cnn.com/video/technology/2018/05/31/concrete-traps-co2-emissions-global-warming.cnnmoney/index.html

I know this is an old post, recently resurrected...people often talk about the carbon footprint while building a structure.  Does anyone consider the carbon footprint over the likely life of the structure?  Second floors require more energy to heat and cool than a first floor only, or a first floor with a basements considerably less.  A 1,200 square foot house with no basement is going to require $xx to heat and cool, but a 700 square foot house with a basement is likely to need 60-70% less energy.  Humidity is often an issue in a basement which windows and well placed fans can sometime address...or the 3 wall basement. Basements are also VERY useful in places with severe weather conditions, and a nice safety feature for families with children or in areas with wild animals...though sometimes children can be considered wild animals ;)  

I disagree entirely with the architecturally based comments on basements.
I find there are often predictable trends with architecture, and each trend lasts a while until the next one comes along.
In my experience, basements can be expensive to create but the advantages of them are great.
If they are created from virgin ground 100% by excavation all sorts of issues can arise, water, cost of excavation, but water can be drained away, but you get a more even temperature in the basement.
In Australia where it is hot and I guess in snow country a basement is practical. If built properly there are no ongoing expences.
Any two storey house has issues of access to do maintenance and of course you have doubled the area that may need maintenance
and increaed the number of windows needed.

CONCRETE USE
Cement is a component of concrete and its the part that has a high energy use during manufacture.
But I believe if used wisely, concretes use can be justified against all the alternative that may require maintenance and are not as effective as a replacement.
There are many other areas one can reduce their carbon footprint which may be more beneficial over a lifetime, than not using concrete.

Today there are alternatives to the 'old portland' cement that work, but you will need to research them.