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Author Topic: Floor tie-in on Interior Drainage System  (Read 3391 times)
Andrew P
« on: April 09, 2008, 10:30:37 PM »

Hi Rod,
Here's a bit of an unusual question regarding an interior drainage/membrane system (the system I must persue in the near future!)

Typically, the floor slab is poured a certain thickness on top of the footings and butts up against the (block) wall.
Does this imply that *some* of the floor mass is supported around the edge of the footings?

So, if a contractor breaks up the floor (12-16"away from the footings), and simply re-fills with concrete, what's to prevent the floor from sinking or cracking around the new concrete.  Wouldn't you need to tie-in the new concrete to the existing floor and existing footings?

It just seems as though you're breaking the floor away from the footings, and it's left to rest all by itself on the gravel base (assuming the gravel hasn't settled. 

I have nightmares of the floor starting to drop soon after the system is installed.

Much appreciated,
Ashburn, Ontario
Rod Johnson
« Reply #1 on: April 14, 2008, 10:37:04 AM »

The floor is suppose to resting on a uniform base. The footing is just part of that base. The floor in a residential home has no structural value and is not designed to rely on the footing for support. If it does, the floor will break close to the footing after a few years unless it is quite thick. (usually)
Floor settlement is a common issue because there are few home builders who actually care about the quality of the base for the concrete, particularly in production homes. After a few years the settlement and cracking is usually done. Therefore, the new concrete edge shouldn't move. None that we have done have shown that symptom.
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