[GSBN] [Gsbn] Fwd: Strength parameters for earthen slabs ?

Fri Jan 24 15:37:46 UTC 2020

Hi Lars

I'm a builder in this jurisdiction who builds straw homes with earthen slabs.  I'm not quite understanding the basis of their question.  The exterior of the home will have some sort of perimeter foundation I assume.  You can get all the required "wind resistance" to be absorbed by that perimeter foundation.  For instance, in the U.S. IRC code, when a floor is framed out of wood we (typically) do not address the floor as resisting these types of forces.  Another method I employ, besides the interior strip footings, is X-bracing on the exterior walls for the shear bracing. So far, I like adjustable cable X's on each wall the best.  I am also doing a lot of straw cell where the house is framed with wood and straw is placed on the inside of the frame, and again the flooring material does not become engineering concern.  Let me know if you need more details on what I'm doing.

Cheers
Doug Nichols

Creating Energy Efficient Homes Since 1995

Nichols Contracting LLC
821 S. 400 E.
Moab, Utah 84532
Cell #970.683.1517
Lic. #9508518-5501

Principal / Qualifying Builder
Community Rebuilds Moab -- http://www.communityrebuilds.org/

________________________________
From: GSBN <gsbn-bounces at lists.sustainablesources.com> on behalf of Dodson Harper <dodson at reginc.com>
Sent: Thursday, January 23, 2020 8:48 AM
To: Global Sustainable Building Network <gsbn at lists.sustainablesources.com>; gsbn at lists.sustainablesources.com <gsbn at lists.sustainablesources.com>
Subject: Re: [Gsbn] Fwd: Strength parameters for earthen slabs ?

Lars

We have also used these floors in many projects but have never had to document to the level that appears to be requested of you here. In one jurisdiction where we are forced to used interior shear walls instead of the resistance from exterior plastered walls, we pour very small strip footings of concrete below the shear walls that tie into our concrete grade beam below the exterior walls. Although this does use more concrete, it is very minimal and can be an easy way to satisfy a building official. See a couple of details below.

Dodson Harper, P.E. S.E.
Principal
REG
Resource Engineering Group
Direct: 970.713.0986
Cell: 970.209.3938
dodson at reginc.com<mailto:dodson at reginc.com>
www.reginc.com<http://www.reginc.com>

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------ Original Message ------
From: "Global Straw Building Network" <gsbn at sustainablesources.com<mailto:gsbn at sustainablesources.com>>
To: gsbn at lists.sustainablesources.com<mailto:gsbn at lists.sustainablesources.com>
Sent: 1/22/2020 10:52:20 PM
Subject: [Gsbn] Fwd: Strength parameters for earthen slabs ?

---------- Forwarded message ---------
From: Lars Keller <larskeller at gmail.com<mailto:larskeller at gmail.com>>
Date: Wed, Jan 22, 2020 at 6:09 AM
Subject: Strength parameters for earthen slabs ?
To: Global Straw Building Network (private, with public archives) <GSBN at sustainablesources.com<mailto:GSBN at sustainablesources.com>>

Help wanted regarding strength parameters for earthen slabs.

We are trying to get permission for a family house where instead of a concrete slab we will use a local product consisting of 0-8mm sand particles with clay.

We have used it in many buildings, it works, but we have never documented it officially.

I have asked the engineer what exactly he needs to sign this off in a legal manner.

Can anyone help ?
Best, Lars Keller

PS: here is a link to the analysis of the earthproduct we use:

https://smallplanetdk-my.sharepoint.com/:b:/g/personal/kontakt_smallplanet_dk/Eek52hjfts5GsgBu7gU4PBYBGfg4JE9r8T7RHoxcsuqyhw?e=5etIzb

- - -

Earthen floors

A single-family house is designed where the usual concrete slab is replaced with an earthen (clay) floor laid on top of a layer of crushed seashells used as insulation. Our main issue is how well this earthen floor can be used to transfer horizontal wind forces, as these are usually transferred by a concrete slab.

Regarding this we have a couple of questions:

What strength parameters do we have for these kinds of floors? -  Such as the characteristic compressive strength, Youngs’ modulus etc.

Can the earthen floor slab be assumed to work as a diaphragm like a concrete slab, or is it unable to transfer horizontal forces?

We have provided a sketch of what we mean by the horizontal wind being transferred through the slab

If you have any questions or there are any unclarity in our questions, please call at 40138786.

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Med venlig hilsen / Kind Regards

Jakob Keller
ingeniør MMT, bygherrerådgiver og medindehaver

E: jk at rbas.dk<mailto:jk at rbas.dk>
M: +45 2297 7222

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