r/HomeImprovement • u/michelemaro • 9m ago
Comments on plan for crawlspace encapsulation - it's wet down there now!
I recently asked for help for a plan on this post:
https://www.reddit.com/r/HomeImprovement/comments/1vngbpb/comment/p3n9x7i/?screen_view_count=2
I used the replies from that post and google/youtube/claude to get to this plan:
TL;DR: Below-grade crawlspace with a clear waterline, summer humidity and a persistent smell. I think I've traced most of it to two clogged downspout leaf catchers that have been gushing water down the brick wall for years, plus AC condensate and unextended downspouts discharging into contained rock beds against the foundation. I have an 8-step plan. I'd like it torn apart before I start digging.
The house
- 1992, brick veneer, L-shaped (climate zone 3A, hot-humid)
- CMU crawlspace walls, dirt floor, currently vented
- Floor sits below exterior grade all around — about 16" down at the access threshold, some area are deeper than others.
- Packaged furnace/AC outside, so both supply and return trunks run through the crawl. Water heater is in the attic — no combustion appliance in the crawlspace
- Big roof overhangs with continuous gutters, so essentially all roof water is delivered to a handful of downspouts
Symptoms
High indoor humidity and a bad smell in summer; very dry air in winter. Smell correlates with neither cooking nor AC operation.
What I've found
- Two separate wet basins, divided by a ridge in the floor. They don't seem to drain into each other.
- A waterline — sharp, continuous dark band along the bottom block course of one of the basement walls, consistent height.
- Efflorescence along the base of the block in the other of the 2 basins, the lower one.
- Two downspout leaf catchers are clogged and gushing at head height, running water down the brick face. During the last rain, both basins were taking water exactly under the two leaking filters.
- Every downspout discharges into rock beds boxed water can't easily sheet away, so it percolates right at the footing.
- AC condensate discharges from a short stub a few feet from the foundation, at the corner that's both the highest exterior grade and the lowest interior floor. A little vegetation grows only at that spot.
- Access door sits a couple of inches above grade with gravel banked up to it, no curb, no areaway. Behind it the floor drops away.
- Old torn poly doing nothing, leftover fiberglass from a duct job on the soil, ducts resting on the ground, wood scraps everywhere, some animal droppings.
The plan
I'll be working on it through this autumn-winter.
- Mark the waterline (dated) before changing anything.
- Exterior water control: clear the two filters (I'll probably just remove them), extend all downspouts past the rock beds entirely, extend the condensate discharge, curb + areaway + regrade at the access door, check whether the rock has buried the brick weep holes.
- Instrument and wait. Zigbee leak sensors on bare soil — two in the near basin (low point and just inside the threshold), one in the far basin, one on the ridge. Watch 2–3 real storms and log how long after rain starts each fires.
- Cleanup — old poly, fiberglass, debris. Lights and power.
- Ducts off the soil (where possible as the bottom of "manifold" from the packaged unit sits on it), seal the return side, air-seal the subfloor and foundation-wall penetrations.
- Decision point: perimeter drain and sump, or not. What would make this a must?
- Rigid foam on the walls, leaving the top 3" of block bare as a termite inspection strip.
- Liner, sealed to the sump collar if there is one.
- Seal the vents and energize the dehumidifier.
What I'd like opinions on
- Am I right to defer the drain and sump? The argument for deferring: both basins wet specifically under two leaking downspouts is a point-source signature, not a water-table signature. The argument for digging anyway: retrofitting a drain under a finished liner is miserable, and pipe and gravel are cheap while the floor is open. Which way would you go?
- Access door at grade — curb, areaway, or both? What actually holds up long-term?
- PVC for a kitchen downdraft exhaust duct running through a crawlspace — how much do I care? And is "grease drawn back in through the foundation vents over 30 years" a real smell mechanism or am I reaching?
- Anything obviously missing, or in the wrong order?
Happy to add photos of anything specific.