In article , Jim Elbrecht says...

Banty wrote:

-snip-
What exactly do you mean by 'rotting' the concrete block?


Constantly wet blocks degrade.

Interior french drain systems usually include a way to drain the bottom blocks
of water, if any, to redirect along with water in the trench.

Usually is a mighty big word. And even if they are installed, a small
weep hole is more likely to clog than a 4" perf-pipe.

?? "big word"

I've seen what B-Dry does. And what Vulcan did on one part of my house. B-Dry
much better - decent sized weepholes in each cavity of the bottom block, very
unlikely to clog. The weepholes *drain into* the trench with the perf-pipe (of
whatever sort). Both are present.


Another advantage [in northern climates] of keeping that groundwater
outside of your house is heat loss. The best insulation is on the
outside of your block under a waterproof membrane. Then the slab and
walls become part of your heat sink. Water running through is a
constant source of 50degree or less coolant.

We're talking about taking groundwater and redirecting it, from just outside the
foundation at the footer, vs. just inside the foundation. How much of a heat
sink difference do you think that is?

BTW, I agree that, at least around here in our clay-shale geology, new
construction should have *both*. But most of us like myself purchase existing
houses.

Banty