Water proofing a underground home

I’m wondering if aircrete would work as a water proof barrier instead of using plastic, for a underground home?
Maybe bed sheets dipped in bees wax would work?
Just curious:)

Why would you think aircrete would work?
From;webpage
Aircrete is simply concrete with bubbles. Regular concrete that we use for our roads, basements, and foundations traditionally made from Portland cement.
This combination hardens into a highly dense material with impressive compressive strength. The addition of iron rebar adds additional structural integrity.
Aircrete reduces or eliminates the traditionally used aggregate.
Instead of including gravel or other coarse aggregate types, aircrete relies on incorporating premade foam pieces that essentially add bubbles of airspace within the concrete mix.
Instead of foam, another option is mixing certain types of reactive substances into the wet cement mix.
The chemical reaction creates gas bubbles within the cement and water slurry to harden with empty cavities.

All I can think of is to use the waterproofing they used to waterproof boats. They have been making boats for 9000 years so maybe use pine tar which is what they used right up to1920 for waterproofing.

But here is the problem. It is not so much that people are not willing to try something beyond asphalt tar or plastic for waterproofing, it is that the cost of failure of experimental materials is going to be devastating. Redigging the earth, then reapplying something else to waterproof, and then reapplying the soil is all really hard work. That is not counting the destruction done to the interior of the home or its contents.

I think it is one of those things that while plastic is bad, maybe by getting something to recycling at least, in an underground home it can be a one and done thing.

Angus Johnson wrote:I’m wondering if aircrete would work as a water proof barrier instead of using plastic, for a underground home?
Maybe bed sheets dipped in bees wax would work?
Just curious:)

Have a look at the work that Mike Oehler has done.  He feels PE if it is buried is OK as a barrier. https://permies.com/t/16965/Radon-underground-structures#147840

Angus Johnson wrote:I’m wondering if aircrete would work as a water proof barrier instead of using plastic, for a underground home?
Maybe bed sheets dipped in bees wax would work?
Just curious:)

There is an entire industry devoted to this subject and it is  the repair and remediation of leaking basements.
There are coatings for outside and inside the basement walls as well as drainage sheets that allow gravity flow of the water on outside walls to what are essentially underground gutters at the base of foundations that take the water away.   For decades an asphalt base substance has been used for roofing and underground sealing but was only good for 15 or 20 years and recently that have come up with elastomeric rubber based coatings that can potentially last forever when using silicone type base formulations.   Just google basement waterproofing.... if you are really serious get all the back copies of WATERPROOFING MAGAZINE  which is a commercial publication publicizing all the products to be used by builders and contractors and how to use them etc.  

Paul what is "PE" please?

John C Daley wrote:Paul what is "PE" please?

G'day John.
Polyethylene.  I was watching a video of Mike Oehler, which I cannot find, but what he was saying that PE exposed to UV is not good because it breaks down and is a pollutant but when used as a waterproof barrier underground is stable and inert so acceptable.  I plan to use PE soon when we make our root cellar as a part of the outside kitchen.

For a natural and less gicky alternative to PE and other synthetics - birch bark! Has been used on turf roofs for centuries, if not millennia. It's waterproof, and just like plastics it doesn't degrade unless exposed to UV light. A few layers of good birch bark sheets laid the right way, without holes and with adequate overlap, will last decades (and according to some a century or more) - provided it's well covered by sod/turf. Don't know how well it'd perform in a true "underground" (ie below-grade) structure, since it's not one continuous sheet, but it definitely works for above-grade turf-covered buildings.

The answer is a most definite NO.  Aircrete will over time absorb moisture like a sponge.


For Paul  F.  PE is polyethylene plastic which is the common modern answer.

As for the bed sheet and wax is this a throw away home or long term home?  If it is just a short term throw away home then wax and sheets will likely work.  But what you need to remember is that everything in that recipe is biodegradable and fairly rapidly in the time scale of homes.  The wax will biodegrade and the threads assuming they are not plastic will biodegrade.  I would expect the wax to fail in a few places given the microbes access to the cotton.  It begins to decay creating a pipeline to other threads.  Thus your layer of waterproofing will start by failing at pinholes and each of those pinholes growing exponentially over time.  As more and more of the wax is exposed to microbes it will begin breaking down too.  Also remember beeswax is expensive when you start buying thousands of pounds of it.  Any other wax for the most part is also made from petroleum products.  Another thing to remember is there are various insects that eat beeswax for food.  Hives are destroyed by wax moths for example.  There are a couple of beetles that also eat it.  Only one egg layers needs to find the way to your wax and you are ruined.

For now I am going to say PE is probably the closest to a Permies acceptable answer in sheeting.  Now multiple layers of bentonite and drainage layers and you can probably accomplish it.  There is a heavy sheeting called Bentomat.  It is mineral bentonite pressed in with a fabric layers to hold it together.  When it gets wet the bentonite swells mostly stopping moisture.  But when wet it is like grease.  This means for the most part it only really works for fairly flat surfaces over the long haul.  One of the plants that produces it is near me.  They produce some 2nds that don't meet standards for sale that are often given away.  So farmers lining canals etc where absolute water tight isn't critical will often go get those rolls.  Be aware these rolls are very heavy and you need a lot of men or heavy machinery to handle them.(think of it this way a 3 foot diameter 12 or 15 foot long roll of dirt that is fairly fragile and can sag like a carpet roll unless supported clear thru or along.

Also remember much of the US is a high radon area so you need to block it too.

C. Letellier wrote:The answer is a most definite NO.  Aircrete will over time absorb moisture like a sponge.
For Paul  F.  PE is polyethylene plastic which is the common modern answer.

Yes, understand that PE is a modern answer.  My comment is based on the fact that Mike Oelher was not a great fan but as a stable product that had no effect of the ground surrounding the structure, he had no reason to rule it out.
I have found the video series.  IMO, it is well worth purchasing it if you do not have free access: https://permies.com/wiki/160756/mike-oehler/Mike-Oehler-Cost-Underground-House

Steve Zoma wrote:All I can think of is to use the waterproofing they used to waterproof boats. They have been making boats for 9000 years so maybe use pine tar which is what they used right up to1920 for waterproofing.

But here is the problem. It is not so much that people are not willing to try something beyond asphalt tar or plastic for waterproofing, it is that the cost of failure of experimental materials is going to be devastating. Redigging the earth, then reapplying something else to waterproof, and then reapplying the soil is all really hard work. That is not counting the destruction done to the interior of the home or its contents.

I think it is one of those things that while plastic is bad, maybe by getting something to recycling at least, in an underground home it can be a one and done thing.

Good luck finding and fixing the inevitable roof leak without causing more leaks.

The plastic membrane will fail eventually, tree roots or animals will penetrate it.

I went looking for old underground houses which never needed roof repair. There don't seem to be any.

Dave Pennington wrote:
Good luck finding and fixing the inevitable roof leak without causing more leaks.

The plastic membrane will fail eventually, tree roots or animals will penetrate it.

I went looking for old underground houses which never needed roof repair. There don't seem to be any.

You might manage quite long (not forever obviously, but long) without repairs... if you do maintenance regularly. For instance, the traditional scandinavian sod roofs (waterproofed with birch bark) have to have the grass cut, preferably on a yearly basis, to prevent shrubs and trees from establishing and wrecking the bark with their roots. I think back in the day they sometimes did this passively, by letting the goats onto the roof...

Hi Anika,

Welcome to Permies.