· by Michael Blair, Nashville's Water Damage
Standing water in a crawl space is common in Middle Tennessee and rarely resolves itself. It comes from a small number of sources, and the cheap fixes come first.
Where does water in a crawl space come from?
Surface water entering through vents or over the footing after heavy rain. Roof water discharged beside the foundation. Groundwater rising through the soil. A plumbing leak.
Which one it is determines the fix entirely, and it is usually identifiable by when the water appears.
What is the cheapest fix for a wet crawl space?
Gutters clear, downspouts discharging well away, and grade falling away from the house resolves a large share of crawl space water at low cost.
Only when that is done does interior drainage make sense, because otherwise you are pumping water that should never have arrived.
- Clear gutters, extend downspouts six to ten feet
- Grade falling away from the foundation
- Then interior perimeter drain and sump if needed
- Vapor barrier over the ground
- Dehumidification once bulk water is controlled
Interior drainage and sumps
A perimeter drain at the footing feeding a sump pump handles groundwater that cannot be excluded. It needs a discharge point well away from the house.
A sump in Middle Tennessee should have a battery backup, because the storms that fill it are the ones that take the power out.
What the water has already done
Wet insulation must come out. Framing that has been damp needs checking for rot and fungal growth. Ductwork sitting in water is contaminated.
And the humidity that standing water produces has been rising into the house, which is why crawl space water often shows up first as a musty smell upstairs.
FAQ
When Water Gets Into the Crawl Space — questions
Is standing water in a crawl space normal?
It is common in Middle Tennessee and it is not acceptable. Water under the house raises humidity throughout, rots framing, ruins insulation and rises into the living space as air moves upward. Persistent damp soil is a problem; standing water is a more urgent version of the same one.
Does a crawl space that floods need a sump pump?
Only after the exterior work is done. Gutters, downspout extensions and grading resolve much crawl space water at a fraction of the cost. A sump is the right answer for groundwater that cannot be excluded, and in this climate it should have a battery backup.
Can I just put a vapor barrier over wet ground?
Not as the first step. A barrier over standing water traps it and does nothing about the source. Bulk water has to be controlled first — drainage, grading and gutters — and then the barrier keeps ground moisture vapor out of the space.
Why do I have water in my crawl space?
Usually one of four sources: surface water entering through the vents or over the footing after heavy rain, roof water from downspouts discharging beside the foundation, groundwater rising through the soil, or a plumbing leak. When the water shows up generally points to which one it is, and that decides the fix.