[Strawbale] Frost Heave

[Robert Tom]

On Fri, 16 Nov 2007 21:58:41 -0500, Hank Carr <hank at dna.ca> wrote:

> Derek Roff opined:
>
>> There is moisture in the environment where most of us live,
>> yes. That doesn't mean that there is always sufficient
>> moisture in the right situation for frost heave to occur.
>
> This is absolutely true.  I didn't say "always".
>
> It really sucks when on those non-always occasions it does happen and it
> happens to you, though.


Frost heave is not some sort of mysterious malevolent force that sneaks  
about waiting to pounce on unsuspecting builders.

It is completely understandable, predictable and avoidable.

As mentioned/described in detail previously, it's simply a matter of not  
providing the right conditions for it to occur. But of course, one does  
first need to understand what one is dealing with.

>> Building codes are an interesting mix of prudent practice,
>> insufficient attention to important details, extreme overkill,
>> and voodoo. Understanding the building science and the
>> specifics of a design and site help one make more refined
>> judgments.
>
> Building codes are intended to protect families, friends, and future  
> owners from people who think they know better and are based on the best
> understanding of the building science at the time that they are written  
> or updated.
>
> We are very fortunate in Ontario to have a brand new building code (less
> than a year since the near complete rewrite

Actually, the Codes are a set of minimal standards below which one risks  
premature building failures and/or risks to occupant safety.

That is to say, a building built to Code is the worst building that the  
law will allow.

People who endeavour to make truly Green buildings invariably exceed those  
minimal Code requirements.

The Codes update process (here in Ontario anyway) occurs once every ten  
years.
Getting new additions to be considered for inclusion in the updates is a  
lengthy process that adds even more time. That is to say, the "brand new"  
Ontario code is already lagging behind current knowledge and other codes  
like the Murrican "Universal" code are even worse.

>> Some frost-protected shallow foundations do not rely on heat
>> loss from the building to prevent freezing. Some do. This is
>> a design choice.
>
> -- From the OBC 2006 Division B Part 9
>
> The NAHB document is equally unequivocal.

Well Hank, I don't suppose you noticed in the NAHB document which you  
cite, the part that mentions that the design procedures outlined therein  
*cannot* be used for insulated slabs  (despite my having already mentioned  
that to you at least once in the recent past)?

And I don't suppose you noticed the portions of the OBC preceding the  
clause which you cite which qualify it ?

First of all, Part 9 of the OBC is the wrong section to be looking at for  
foundation design.
Hint: First look at the section that pertains to the design of shallow  
foundations for all buildings, not just housing and small buildings.

Second, if one were to interpret the Code in the manner that Hank has,  
superinsulated foundations which minimise heat loss to the earth on which  
they sit, would not be permitted. That is obviously ridiculous.

Even without the Code requirements WRT foundation design, it would be  
foolish to design a foundation which relies upon heat loss from the  
building interior to prevent frost heave.

Mechanical systems that provide the means to keep a building heated have a  
nasty habit of failing at inopportune times.

People who operate those mechanical systems cannot be relied upon to  
ensure that the mechanical systems are in fact operating when they should  
be.

The infrastructure that delivers the means to operate those mechanical  
systems are not fail-safe.

$#!+ happens.

Failure of any one of the above could result in freezing/frost heave of a  
foundation that relied upon heat loss from the interior of the building  
for integrity.




-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at chaffY a h o o  dot  c a >
manually winnow the chaff from my edress in your reply