The situation

Illustrative example. Not a real job or customer.

A hypothetical 1950s brick ranch has a family room added along the back sometime in the 1970s. The original house sits over a crawlspace with a hatch in a hallway closet. The addition has its own shallow crawlspace with no hatch at all. The owners notice a musty smell in the family room that gets worse in summer, and they have shampooed the carpet twice without improvement.

  1. The owners check the main crawlspace and find it reasonably dry, with an old but intact plastic liner.
  2. At the far end, they see that the original foundation wall separates the main crawlspace from the addition, with only a small opening between them.
  3. A contractor looks through the opening with a camera and finds bare soil, no vents, damp air and heavy growth on the addition's floor joists.
  4. A downspout at the inside corner where the roofs meet discharges right against the addition's foundation.
  5. The contractor proposes cutting a proper access, containing the pocket, cleaning the joists, replacing the insulation, and extending a liner and drainage fix.

With the downspout extended, the pocket cleaned and dried, and a ground cover installed, the family room smell faded over the following weeks. The carpet, which had never been the source, stayed.

Decision points along the way

  • IfCarpet cleaning did not change the smellThe owners correctly stopped treating the room and looked below it.
  • IfThe main crawlspace looked fineRather than ending the search, they checked for parts of the house it did not reach.
  • IfThe pocket had no accessA camera through an existing opening gave a look without demolition.
  • IfA downspout pointed at the cornerFixing it was the cheapest part of the job and the one most likely to prevent a repeat.

What helped and what could have gone wrong

What went right

  • Mapping which foundation was under which room
  • Finding the outside water source before cleaning
  • Containment set up before cutting a new access

Common missteps in this pattern

  • Replacing carpet and pad with no change in odor
  • Running an ozone machine in the living space
  • Sealing the opening between crawlspaces and trapping more moisture

If your house has an addition

  • Find out what foundation type sits under each part of the house
  • Look for every crawlspace and how each is reached
  • Check downspouts and grading at inside corners
  • Note which rooms smell and when
  • Ask any inspector to look at the junction specifically

Common questions

Is a hidden crawlspace pocket common?
It is a pattern worth checking in any ranch with an addition. Builders sometimes left the old foundation wall in place as a divider and gave the new crawlspace no access of its own.

General information for Wheat Ridge, not a quote or professional advice. In an emergency, call 911.