Ann Arbor particulars
Washtenaw County is one of the nine Michigan counties in EPA's highest radon zone, Zone 1, where the predicted average indoor level is above 4 pCi/L. EGLE says the residential code requires radon-resistant construction in new homes there, but that rule does not reach an existing house, so testing is still on you. Ann Arbor's fee schedule, revised July 15, 2025, treats basement waterproofing as a building permit that also requires grading plan review and a grading permit, with a $15 base application fee and a permit fee of $100 plus $10 per $1,000 of project cost.
Applications go through STREAM; the office is at 301 E. Huron St., 734-794-6263. The city's flooding page says basement water can come from storms, spring snowmelt or groundwater building up, and advises a backup for the sump pump. Of 53,715 housing units, 64.3 percent predate 1980, 30.5 percent predate 1960 and 15.2 percent predate 1940, and the median value is $435,100, high enough that an engineer's report is small next to the bill. Ypsilanti is 6.0 miles away.
Crawl space encapsulation in Ann Arbor: what to know
EPA predicts an average indoor level above 4 pCi/L for Washtenaw County, and EGLE says the Michigan Residential Code requires radon-resistant construction in new homes there. That rule applies to new construction, not to an older house you are encapsulating, which is why a test matters. EPA says submembrane suction, a plastic sheet with a vent pipe and fan, is the most effective method in a crawlspace home.
The city's building fee sheet does not name crawl space work, so call 734-794-6263 to ask about permits. Encapsulation under R408.3 is a sealed Class I vapor retarder plus conditioned or exhausted air; it is optional and vented crawl spaces stay compliant. About 30.5 percent of the housing predates 1960, and our radon guide shows how to test.
Permits for crawl space encapsulation in Ann Arbor
Nothing we found lists encapsulation as a permit item.
Many cities run their own building department, so start by asking the City of Ann Arbor building department who issues foundation repair permits.
When a damp crawl space counts as an emergency
- Water is standing in the crawl space near wiring or a furnace. Do not wade in.
- The floor above is sagging or a support has moved.
- A musty smell in summer.
- Condensation on cool pipes or the rim joist.
What to check before you call about a crawl space
Try this first: run a short-term radon test on the lowest livable level before you hire anyone.
- Look at the ground and the floor above with a flashlight, and note standing water, wet insulation or a smell.
- Buy a humidity meter and read it over a few weeks.
- Ask any company to say in writing what it measured.
What crawl space encapsulation costs
The estimate below is the Michigan-wide one, adjusted for Michigan wages and not for Ann Arbor in particular. The same table is on the crawl space encapsulation page. How we estimate costs. Prices as of Oct 19, 2026.
| Item | Figure | What it is |
|---|---|---|
| Estimated range, not a quote | $2,300 to $15,300 per project | Built from 2 national published ranges, adjusted by the Michigan carpenter median wage ratio (1.02). No Michigan foundation company price is shown, because none of the companies we looked at published a price we could count. |
| Estimated range per square foot, not a quote | $3 to $12 per square foot of crawl space | Built from one national published range, adjusted by the Michigan carpenter median wage ratio (1.02). No Michigan foundation company price is shown, because none of the companies we looked at published a price we could count. |
| Carpenters, Michigan median | $61,680 a year | What workers are paid (BLS 2025 data via O*NET), not what you are charged. |
| Construction laborers, Michigan median | $49,590 a year | What workers are paid (BLS 2025 data via O*NET), not what you are charged. |
| Building permit, Sterling Heights | $56 application fee | 2026-27 application. No encapsulation line. |
| Building permit, Grand Rapids | $79 for work valued at $1 to $1,000; $215 at $20,001 to $21,000 | FY2027 chart. No crawl space line. |
| Building permit, Lansing | $175 for work valued at $4,001 to $10,000 | Schedule of July 1, 2026. |
How we estimate costs: the Estimated range row is a model, not a quote. It takes two published national ranges for this job (cost guides from third-party sites that we have not verified and do not cite) and multiplies them by Michigan's carpenter median wage ratio to the US (1.02, BLS 2025 data read through O*NET OnLine). No permit fee is added: the city permit rows below are shown as printed. The wage and permit rows are what workers are paid and what a city's own schedule charges, and neither is a price. Your soil, water and the repair method move a real quote well outside any range, so get an independent diagnosis first. We have not collected quotes, and we found no Michigan foundation company that publishes a price we could count. Full method.
Questions about crawl space encapsulation
Do crawl spaces need encapsulation?
Not under the code we read. The 2015 residential code allows a vented crawl space, and allows an unvented one built to R408.3, so encapsulation is a choice and not a requirement.
Is a dehumidifier required in an encapsulated crawl space?
The 2015 code section we read does not name one. It requires continuous exhaust or conditioned air at 1 cfm per 50 square feet, and does not name a liner thickness either.
What humidity should an encapsulated crawl space be?
No government agency we read sets a target for a crawl space. EPA's figure of below 60 percent, ideally 30 to 50 percent, is for indoor air, and a humidity meter costs about $10 to $50.