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clarification of usable space as it pertains to foundation drain requirements.

D

DNA

Registered User
Joined
Sep 7, 2022
Messages
14
Location
Bayfield Colorado
Hello everybody,
RE: 2015 IRC section 405.1 states: Drains shall be provided around concrete or masonry foundations that retain earth AND enclose habitable or usable spaces below grade.
Looking for clarification on when a foundation drain is required. Understood for basements. The confusing part "usable space". Our local requires footing to min. 32" below finished grade. Most builders in my area create a crawl space. The space between top of footer and bottom of floor framing is generally 24". Is a foundation drain required?
 
The only thing I would add to Steveray's post is if they are locating mechanical equipment in there.
 
steveray said:
Do people typically use them for storage or anything?...There is your definition....
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Well there is no telling how people will use the crawl space.
My first thought was along the same lines of your response. However, there is no definition in the code regarding "usable space" as there is for "Habitable space".
If a contractor says a foundation drain is not required, based on what the code says, it is difficult to argue. Just looking for some ammunition.
 
DNA said:
Most builders in my area create a crawl space. The space between top of footer and bottom of floor framing is generally 24". Is a foundation drain required?
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A crawl space is generally a dirt floor and does not support a use. Water intrusion should not be an issue as long as the exterior grade slopes away from the building.
 
R408.6 Finished grade.
The finished grade of under-floor surface shall be permitted to be located at the bottom of the footings; however, where there is evidence that the groundwater table can rise to within 6 inches (152 mm) of the finished floor at the building perimeter or where there is evidence that the surface water does not readily drain from the building site, the grade in the under-floor space shall be as high as the outside finished grade, unless an approved drainage system is provided.
 
ICE said:
A crawl space is generally a dirt floor and does not support a use. Water intrusion should not be an issue as long as the exterior grade slopes away from the building.
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Thank you for your response. Currently we are experiencing high run - off from snow melt thereby affecting the water table. I have had a number of call from people with water in their crawl space. If I start insisting on foundation drains I get a lot of push-back. That's when I throw out the "Cheap insurance" statement.
 
2018 IRC definition
[RB] CRAWL SPACE. An underfloor space that is not a basement.

Are they conditioned crawlspaces or unconditioned? Is a vapor barrier installed? How is the moisture being delt with/removed?

Are they meeting the requirements of IRC 408?
 
mtlogcabin said:
2018 IRC definition
[RB] CRAWL SPACE. An underfloor space that is not a basement.

Are they conditioned crawlspaces or unconditioned? Is a vapor barrier installed? How is the moisture being delt with/removed?

Are they meeting the requirements of IRC 408?
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Thank you for your response. Yes they are constructed per the codes minimum requirements. Some are conditioned and some are not. There is proper ventilation either from code required vents or by mechanical ventilation system.
The question is pertaining what is what is considered "usable space", as there is no clear definition in the codes
 
I wouldn't consider it "usable" unless it's deep enough to meet ceiling height requirements.

Unfortunately the contractor seems to be more interested in saving $50 worth of pipe & gravel than the owner possible having to spend several thousand dollars if there is a water problem.
 
Paul Sweet said:
I wouldn't consider it "usable" unless it's deep enough to meet ceiling height requirements.

Unfortunately the contractor seems to be more interested in saving $50 worth of pipe & gravel than the owner possible having to spend several thousand dollars if there is a water problem.
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Thank you for your response.
Your response describes the dilemma. The code is ambiguous regarding "usable space". While I would like to require all foundations in my area have foundation drains, I cannot do so through the building codes.
The Town is getting ready to adopt new I-Codes, and I think I will propose an amendment to the code with the fdn drain required.
We will see how they accept my amendment.
 
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