From: tanner@bcsaic.boeing.com (Jim Tanner)
Newsgroups: misc.consumers.house
Subject: Re: Another wet basement (a new approach)
Keywords: basement, water, drain, sump
Date: 21 Jan 93 19:54:12 GMT
Distribution: usa
Organization: Boeing Computer Services, Seattle

In article <1993Jan19.205122.14796@noose.ecn.purdue.edu> merrifie@cidmac.ecn.purdue.edu (Michael C Merrifield) writes:
[ discussion about how water is getting into basement, and why he doesn't
[ want to do a standard (outside) perimeter drain ]
>
>My approach gets to work on the problem before the water level equals
>the floor level but isn't as "extreme" as above.  Creating a 4" x 4"
>trench around the perimeter means removing less that a cubic yard
>of material.  Basically, I would remove the floor about 4" from the wall.
>Then install a 2" pipe with holes drilled along the sides (probably can't
>find 2" drain pipe) in the bottom of the trench and surrounded by gravel.
>I would also drill "weep" holes into the hollow core of the block wall
>as low as possible (below floor level) to facilitate the flow of water
>into the trench.
>
>  |   |        |   |
>  |  Concrete  |   |
>  |  Block     |   |<-- ~4" -->
>  |   |        |   |----------+---------------------------
>  |   |        |   |oooooooooo|                       
>  |   | weep   |   |oooo_ooooo|       Basement Floor   
>  |   | hole-->|===|ooo( )oooo|                         
>----------------------------+ooooooooooooooo pea gravel oo
>                        ^   | --     - --- -- -- -  --  -
>                        |   | - --     - --- -    --- - 
>           drain pipe --+   | ---   --   - --- --   -- -
>                            | --  - --- --- -  - ----  --
>   Foundation               |  --     - --- -- -- -  - -
>                            | -  -  - ---   - -- -  -- 
>----------------------------+ ---  -  - --- -- -  -  - -
>--   --   -   --  -    --   - --  -    - --- --  -- -  -
>
>I am counting on two local variables: 1) the 1" layer of pea gravel under
>the slab and 2) hollow core of block wall is actually hollow.  Several
>holes drilled at floor level seem to indicate that this is the case.
>
>One question is the ability of the 2" pipe to drain water to the sump with
>out much slope to the run of pipe.  Even if I have to install another sump,
>this appears to be a viable alternative.  It also seems like an improvment over
>the passive, open-air trench systems used to direct water to a sump.  In
>addition, any "above floor" approach can be used as a back-up to this system.
>If I implement this plan, I will leave the trench un-finished to watch
>for overflow problems.
>
>Any comments or suggestions appreciated!

In your estimation of effort involved, it will be more difficult to
remove the basement floor (concrete) than the exterior fill (dirt),
certainly on a per-cubic-yard basis.  I presume you will need to rent
a concrete saw to cut through the basement floor, then break up the
material to be removed with a sledge hammer (or rent an electric
jackhammer).  There will probably be some rebar or reinforcing mesh
embedded in the concrete that you will have to contend with, too.

In estimating difficulty of exterior excavation, there are some power
tools that can help.  Even if you can't use a backhoe, you can use a
"demolition hammer" (sort of a scaled-down electric jackhammer that you
can hold in your hands, on which you can fit various bits, in particular
a smallish shovel-like bit) to break up the dirt, so you don't have to
use a pick.  Then it's mostly a matter of manually shoveling out the
material; maybe bring in a bunch of friends some weekend, with free beer
and pizza?  Take heart - it _is_ doable.  One friend of mine excavated
(by hand) a 15x20 basement area under a sunroom that was originally
built over a crawlspace; another excavated (again by hand) a 10x25
basement area under a porch that he was replacing.

You don't mention the geometry/size of the basement, nor the ground
elevation/basement depth around the house, so I can't get a feel for
the difficulties involved in an exterior drain, but IMHO I'd install an
interior drain _only_ as a last resort, if only because it seriously
complicates any future finishing off of the basement (maybe you aren't
interested in finishing it off, but the next buyer might be).

BTW, I've heard the term "French drain" used to describe interior
drain systems such as you've sketched out.
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