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Greenbuilding Archive for February 2002
458 messages, last added Tue Nov 26 17:26:37 2002
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Keying a foundation wall into the footing - which simply means having the 
concrete guys float a 2x4 into the top surface and then pull it out in time 
to insert the rebar, and using one of many of the avaiable variations of 
bentonite clay-imbibed tube-like foundation seals (placed along the joint 
between footing and foundation before backfill) works wonderfully and avoids 
the entire question of where to put the foundation drain - it simply lays in 
the trench roughly at the top of the footing.

this has been my practical experiance, for what it's worth.

Later,  Jim
Saint Louis

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<HTML><FONT FACE=arial,helvetica><BODY BGCOLOR="#ffffff"><FONT  SIZE=2>Hi All (and Sacie!)
<BR>
<BR>Generally, foundation drains are done not by what we draw in the documents or wall sections, but are governed by the footing excavation process itself.
<BR>
<BR>Most often, a backhoe with an appropriately sized scoop cuts the trench for the footing directly into undisturbed soil. &nbsp;Once the footing is poured, keyed or not, the formwork for the foundation wall is assembled and the "french" or "trench" drain is laid out along the joint between foundation wall and footing top prior to backfilling. &nbsp;
<BR>
<BR>To place the foundation drain below the top of the footing would require that the footing be "formed" in a trench larger than the resulting footing. &nbsp;There are cases this may be a true advantage, but in general it merely amounts to more work and a measure of confusion on the part of the earthwork guys and the concrete guys as to what in the world is going on.
<BR>
<BR>From my experience, the biggest advantage of any kind of perforated drain pipe around the lowest below-grade level of a building, is to provide an area of negative pressure for migrating water to seek out - then linked to a sump pump or a storm drain. &nbsp;In an ideal situation we would surely slope all foundation drains in the same manner that we slope sanitary waste lines. &nbsp;The problem with that line of thought is that often there is no reliable level line to work from (earthwork and concrete guys rarely use laser level transit devices - except to determine the top of their walls)
<BR>
<BR>Keying a foundation wall into the footing - which simply means having the concrete guys float a 2x4 into the top surface and then pull it out in time to insert the rebar, and using one of many of the avaiable variations of bentonite clay-imbibed tube-like foundation seals (placed along the joint between footing and foundation before backfill) works wonderfully and avoids the entire question of where to put the foundation drain - it simply lays in the trench roughly at the top of the footing.
<BR>
<BR>this has been my practical experiance, for what it's worth.
<BR>
<BR>Later, &nbsp;Jim
<BR>Saint Louis</FONT></HTML>

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