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Foundations.

 
dan simon
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Im not sure where to post this. Im sure someone can figure that out.
I have been reading quite a few posts here and find myself quite horrified with the lack of good foundations on many builds of which people hope the buildings will last for some time.
I understand that not every build is the same. The main differences being soil condition, ground water, building materials and cost.
However is there some possability of a thorough discussion that could lead to some viable foundation models that could be adapted for specific needs. Its just terrifying seeing some of the stuff you guys have come up with.
 
Jack Edmondson
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Location: Central Texas zone 8a, 800 chill hours 28 blessed inches of rain
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dan simon wrote:
However is there some possability of a thorough discussion that could lead to some viable foundation models that could be adapted for specific needs.


Dan,

I imagine there is plenty of room and interest in that discussion. Perhaps you could frame the conversation by defining what a "good foundation" looks like to you.
 
dan simon
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the elements of a proper foundation are neccessary for the protection of the building. to effectively do this there needs to be in place ,
1. Drainage. Drain the first few inches of soil as well as drain water that will effect the base of the foundation (the footer or peer). drainage also need to incorporate a plan for removing water that is shed from the roof. Drainage would also include moisture under the floor taken to the sump or day lighted outside the subsurface drain. so effectively 4 drains or 4 areas to drain.
2. the actual foundation. my home is a post and beam with straw bale infill. my foundation is both a rubble foundation with a bond beam that supports the straw bales and peers on the inside of the house supporting the structure of the house. I used concrete for the peers. this is what i knew how to do. im not sure what alternatives there are for concrete peers that incorporates both the downward pressure of the posts and roof and also the upward pressure of wind or updraft. think tornadoes. the peers are 2 feet deep, frost here is 18 inches this is to code. I only used sonatube above the excavated ground level. i used metal post bases to attach the peer to the posts. the peer also rises to the finished floor level. i narrowed the last 2 inches of the peer down to 6 inch. the straw bale foundation is a 2 foot deep 18 inch wide rubble trench with a 4 inch french drain under the rubble that drains to daylight about 20 feet way well below the base of my foundation grade. the edges are lined with silt screen and filled with gravel. on the top of the foundation is a concrete bond beam 4 inch think and on top of this beam is 2 2x4 pressure treated wood strips that the bales sit on. these are there to separate the concrete from the bales. I now know there are alternatives to concrete however im not sure how to implement them. the top of the concrete bond beam sits at my finished floor grade and is 4 inches above the outside grade.
3. The roof. my roof has 3 foot over hanging eaves. this worked very well as i had exposed bales for over a year and had no water on the even though i get 60 inches a year here. with gutters draining off and tying into the sub surface level french drain. the subsurface drain is just under the outer edge of the house eaves and just under the gravel walkway i have around the house. this drain daylights also 20 feet away from the house. and finally the subfloor drain drains into the foundation drain. to do this i tapered the subfloor under my sub gravel so it drains to the back of my house.
This may not be perfect however i use current engineering standards to mix my concrete and to sized my peers. i also made sure i met frost standards for my area and new the local soil standards.
 
Terry Ruth
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I have been reading quite a few posts here and find myself quite horrified with the lack of good foundations on many builds of which people hope the buildings will last for some time


1. Drainage. Drain the first few inches of soil as well as drain water that will effect the base of the foundation (the footer or peer). drainage also need to incorporate a plan for removing water that is shed from the roof. Drainage would also include moisture under the floor taken to the sump or day lighted outside the subsurface drain. so effectively 4 drains or 4 areas to drain.


Sump as in pumps, basements, define piers are gravity feed no pumps? This has been discussed in depth start by looking @ JC White Cloudes " Raised Earth Foundations", my many post, and look at Bill Bradbury's post, not sure what threads/post you have been reading but since the other two pros do not post here anymore I can answer any questions you may have. The Science of soils and and how well they drain needs a soil test and/or geo tech report otherwise it is heresay! Unfounded in any data and nothing but opinion. Vapor uptake is an issue under most floors not liquid water drainage too entirely different moisture issues. One can exist without the other depending on ground pressures and ventilation.

I used concrete for the peers.


Piers if not analyzed by a PE and geotech will more than likely fail in time.

this is what i knew how to do. im not sure what alternatives there are for concrete peers that incorporates both the downward pressure of the posts and roof and also the upward pressure of wind or updraft. think tornadoes.


I can tell you are not a PE it has nothing to do with pressures like burst pressures in plumbing, everything to do with mechanical properties such as static dead weight & compression strength, tension at the anchors to resist uplifting, dynamic bending moments from wind and seismic.

the peers are 2 feet deep, frost here is 18 inches this is to code.


2' may be inadequate depends on a soil tested PI, MC, sieve size, index. Frost heaving is a concept code does not address well, too may variables. IRC code points you to CH 3 a geotech or PE.

I only used sonatube above the excavated ground level. i used metal post bases to attach the peer to the posts. the peer also rises to the finished floor level. i narrowed the last 2 inches of the peer down to 6 inch.


Perhaps a good idea to taper but not in all load cases since the cross section at the taper will take less load that would have to be resisted by the proper depth and size of the steel anchor only proper analysis by a PE can determine.

the straw bale foundation is a 2 foot deep 18 inch wide rubble trench with a 4 inch french drain under the rubble that drains to daylight about 20 feet way well below the base of my foundation grade.


Sounds good BUT I have never seen any data to prove a RT per some given thickness, width, keeps capillary uptake pressures away from strawbale if you have please post the data.

the edges are lined with silt screen and filled with gravel.


No need if you have a good positive grade most of the capillary action is vertical not lateral. The silt screen can block access to soils moisture content(IE: Mag bentonite would be good, Kaolin would not) depending on how permeable it is or if it acts as a vapor barrier, like smart or not so smart house wrap.

on the top of the foundation is a concrete bond beam 4 inch think and on top of this beam is 2 2x4 pressure treated wood strips that the bales sit on.

2. the actual foundation. my home is a post and beam with straw bale infill. my foundation is both a rubble foundation with a bond beam that supports the straw bales and peers on the inside of the house supporting the structure of the house.


If you are talking about a wood grade beam = termites. A better approach a concrete stem wall that supports a wood frame chase with a capillary break.

these are there to separate the concrete from the bales.


What moisture transfer action are you separating? Wood can only adsorb 20% along the grain, less than half that transverse grain as you are placing it, by volume then it rots if it does not dry in 24 hrs proven. See my breathable walls thread.

I now know there are alternatives to concrete however im not sure how to implement them.


Again, read the site more there including JCW thread and mine we discuss many.

the top of the concrete bond beam sits at my finished floor grade and is 4 inches above the outside grade.


Capillary uptake pressures have been proven to reach many feet not inches without the proper break.

3. The roof. my roof has 3 foot over hanging eaves. this worked very well as i had exposed bales for over a year and had no water on the even though i get 60 inches a year here.


In most cases 18-24" is plenty anymore if other design features are in place or can block solar gains or be a waste of framing cost.

with gutters draining off and tying into the sub surface level french drain.


Good! Take that to a cistern or rain catchment system.


the subsurface drain is just under the outer edge of the house eaves and just under the gravel walkway i have around the house. this drain daylights also 20 feet away from the house. and finally the subfloor drain drains into the foundation drain. to do this i tapered the subfloor under my sub gravel so it drains to the back of my house.


Sounds good IF you have good postive drainage but wonder about the strength of the taper.

T
his may not be perfect however i use current engineering standards to mix my concrete and to sized my peers.


What standards" ACI?

i also made sure i met frost standards for my area and new the local soil standards.


Please post what standards you designed to along with how you tested to verify they were met along with design_build plans, photos, etc..

I run CFD WUFI models tested and proven that take into account accurate and internationally proven boundary conditions, weather files, indoor climate conditions, mold analysis, on my foundations and buildings, and I struggle as many building scientist do. I get a kick out of reading threads like this Testing foundation soils next to impossible without the proper design and instrumentation tools and teams of Engineers, BUT i can get extremely close or 100% accurate since I have the tools and knowledge.
 
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