P2A: DIY Dryer Vent Repair



Fix the dampness on the concrete wall behind the dryer; confirm it is indeed the dryer vent dumping hot air, not an overall moisture problem; re-insulate and re-finish the wall. Finally run a new dryer vent.


Mold can be a serious health hazard and shouldn’t be underestimated. Wear gloves, a face mask, and eye protection. You don’t want to spread the spores anywhere, but outside.  If you can use a hepa-filtered vacuum that vents out a window, do so. Also since you’re going to be using chemicals read the label twice and make sure you understand it. You don’t want to call poison control, but if you have to make sure you have their number handy.

The dust from sanding is also not good for you. Again cover your face and eyes and work in a well-ventilated room.

When painting, make sure the room stays well ventilated.

When working with the aluminum vent, it is sharper than it looks. Be aware.


  • hammer
  • Philips screwdriver (electric or on a hammer drill)
  • tape measure
  • pencil
  • utility knife
  • level or a straight edge
  • drywall mud knife
  • paint brush
  • paint tray
  • staple gun
  • fan
  • spray bottle



This will take a few days. You need to let the wall dry out then clean up any dead mold and you need to let your drywall compound dry before you sand and paint.

Job Plan

  1. Seal up the room. As you are dealing with moisture behind a wall prepare for the worst.
  2. Using your straight edge or level and a pencil, mark the area of the wall you intend to remove. Then use the utility knife to cut the section out. Best practice is to cut a hole from halfway of one joist to halfway of the nearest joist outside your problem area. You want to cut a hole that you can replace with a single piece if at all possible.
  3. Once you have cut straight lines separating the wall to be removed from the wall remaining, you can begin tearing out the drywall with the hammer.
  4. As you proceed, remove any drywall screws from the joists that you come across.
  5. Once all the old screws and drywall has been removed, cut the clear plastic vapour barrier and remove.
  6. Wearing gloves, remove the insulation from between the joists.
  7. If the tar paper wrapping is damp; it will likely disintegrate if you touch it.
  8. Spray the Concrobium on any discoloration on the wood, wall or visible signs of mold growth
  9. Set up the fan to produce a breeze over the exposed area and let set for until dry (this could be be 24 hrs. or more).
  10. With the wall dry, cut the rigid stryofoam board to fit between the joists against the tar paper (or against the concrete if the tar paper has disintegrated)..
  11. Layer your insulation against the stryofoam as required. I put three layers of rigid stryofoam in my three exposed joist spaces because I had excess board; this is likely not required.
  12. Cut a sheet of clear plastic to cover the exposed area. Tuck the plastic underneath existing drywall where possible and attempt to create as smooth a seal as possible. Common wisdom now is that vapour barriers are never air tight; don’t worry if yours isn’t. Staple the plastic into place.
  13. Using your pencil, tape measure and straight edge cut the dry wall to cover the hole in your wall. You want to do so with as few pieces as possible: one being optimal.
  14. Screw in the drywall.
  15. With your drywall replaced, spray adhesive along the seam and apply your drywall tape.
  16. Mud the tape and the sunken screw heads.
  17. Let it dry then sand and re-apply mud as required then sand again.
  18. If you have a nice smooth, perfect wall paint it. If you don’t repeat the last step until you do.
  19. Connect your dryer vent components with metal screws.
  20. Use aluminum tape to seal and joints.
  21. Connect your new vent to the dryer on one side and the outside world on the other.


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