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ecrhone 12-08-2009 11:08 AM

Pouring concrete in dirt floor basement of old home
I have a home build in 1872. Part of the basement has a dirt floor (31'X14').
The basement had 10ft high ceiling. Perimeter foundation walls is masonry and the interior walls are brick. The basement has had issues with moisture, but I think that the culprit is the lack of roof gutters. I will be either adding gutters or a french drain. My problem, I would like to pour concrete and turn the dirt floor area into a wood-shop. So the floor will need to withstand some heavy equipment. My question, how do I pour against the brick and the masonry? If I need forms. what type do I need to build.


lou19604 12-21-2009 05:08 PM

1 Attachment(s)
I,m gonna assume you considered the rock and grate plus leveling the floor. to make it easier if your gonna pour a 6" slab then i would use 1x6 boards.
2 ways

1st you can use the 1x6,s on all 4 sides then fill in after it dries

2nd you can use 2 1x6 on the inside corners and just fill in with the eyeball level

However i would condsider where my heavy machines are going and dig that area out a little so i could make a thicker pad in that area

Dont forget to grove the pad

itsreallyconc 12-22-2009 03:58 AM

' grove the pad ' ? ?

inspectorD 12-22-2009 05:40 AM

Expansion joint, only not as deep. If you groove the pad, it gives it a weak point to crack ...less noticable, but still risky.

lou19604 12-22-2009 04:16 PM

EXSPANSION JOINT much better choice thanks for catching that.

GaTomCat 01-14-2010 05:36 PM

between the concrete floor and the walls...use a 1/2" thick bituminous expansion joint stuff [a wood board will rot out an can be a termite issue]...if the equipment is very heavey..pour 6" slab with 4,000 psi concrete...use #4 rebar [24" on center] rather than wire mesh and have control joints no more than 12 feet apart..

ecrhone 01-15-2010 01:40 PM

Thanks for all the tips. I'm going to start the project in a few days. I'll post pictures.


mudmixer 01-15-2010 03:28 PM

Some codes require the slab to be poured in contact with the walls to provide additional lateral resistance/support.

Placing concrete on "dirt" is never a good idea. Since it open, I would put in gravel and interior drain tile to minimize moisture.

The joints in the slab should not be exspansion joints or expansion joints and they are control joints to control wher the shrinkage cracks may occur. Concrete in a basement slab does not expand.


itsreallyconc 01-16-2010 04:22 AM

this may be too late - don't forget a vapor barrier NOW under your conc floor - its pennies to do it right NOW & much more expensive after the conc cures.

idea of interior drains're good, too,,, no time like the present to save $

control joints're normally saw'd or groov'd however 1 CAN use expansion jnt mtl - why i don't know as its more $ albeit not much !

conc doesn't change dimension unless its subject to temp swings - after you place/finish it, it WILL be smaller than you expect due to hydration taking the wtr OUT of conc,,, after curing, because basement temps tend to remain constant, there'll be no external forces influencing conc dimensions - high school physics !

ecrhone 01-19-2010 07:47 AM

Thanks for the additional tips. I saw online (
) where a couple of guys poured the perimeter of the room first. Once it cured, then the middle area was poured. Pouring the perimeter first provided them with a great work surface. This technique appears to make working within existing masonry walls easier.


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