Two buildings stitched together
Additions in Wheat Ridge range from 1960s family rooms built a few years after the house to recent primary suites. Each one was built with the methods, foundation and budget of its time. It is common to find an original basement next to an addition over a crawlspace, or an original crawlspace beside an addition on a slab.
Where the two meet, several things can go wrong at once. The roofs join in a valley that concentrates rain and snowmelt. The foundations may settle differently, opening a crack. The crawlspaces may connect through a narrow gap with no ventilation, or be separated by an old exterior wall that now sits in a dark, damp pocket. Moisture collects at these seams and mold follows.
Junction problems and their clues
| Problem | Clue inside | Clue outside or below |
|---|---|---|
| Roof valley leak at the tie-in | Ceiling stain along the old exterior wall line | Debris in the valley, worn flashing |
| Foundation crack between old and new | Musty odor in the room next to the seam | Damp soil or efflorescence at the joint |
| Dead-air pocket between crawlspaces | Floor feels cold and smells musty | No vents or ground cover in the pocket |
| Old siding left inside the wall | Stain where the original wall was | Rotted siding or sheathing visible from the crawlspace |
| Grading that slopes into the corner | Damp carpet in one corner | Downspout or patio draining toward the joint |
What to inspect at the seam
- The roof valley and flashing where the rooflines meet
- Gutters and downspouts near the inside corner
- Both crawlspaces, including any connection between them
- The underside of the floor along the old exterior wall
- Ceiling and wall finishes on the line of the original exterior wall
- Patio or walkway slope at the inside corner
Questions for an inspector or contractor
- Did you look at both crawlspaces and the connection between them?
- Is any original exterior siding or sheathing trapped inside the wall and damaged?
- Where is water entering at the junction, and how will that be corrected?
- Will containment cover both sides of the seam if growth extends across it?
- Does the repair involve structural or roofing work that needs a permit?
Common questions
- Why does only the room next to the addition smell?
- Air from a poorly ventilated pocket at the junction often leaks into the nearest room through gaps around the floor or old wall. That room becomes the outlet for the hidden moisture.
General information for Wheat Ridge, not a quote or professional advice. In an emergency, call 911.