How to Add Attic Storage Without Losing Insulation, by Mohawk Valley Handyman on YouTube. 1 min 20 s.
- Video length
- 1 min 20 s
- Time to do it
- 6 hours
- Difficulty
- Medium
- Steps
- 9
What you need
Steps
Measure the joist spacing, depth and span, and check for sagging or cracked wood. Storage adds load, so stiffen or sister any weak joists before you build.
Air seal first. Fill gaps around wires, pipes and the tops of walls with caulk or spray foam so warm air stops leaking into the attic.
Check that the insulation between the joists sits at full depth and is not compressed. Fluffed insulation only works at its stated thickness.
Plan the storage area. Keep 2 feet clear around the chimney, leave soffit baffles and vents open, and mark a clear path from the hatch.
Lay 4 inch rigid foam board across the joists. Two 2 inch layers work well. Cut pieces with a utility knife and stagger the seams.
Tape all foam seams and edges with foil tape, and seal around pipes and wires so the foam layer stays continuous.
Set OSB or plywood sheets on the foam and screw them down with long deck screws that reach into the joists, not just the foam.
Screw down every sheet at the edges and middle, sink the heads flush, and keep gaps between panels under 1/8 inch.
Check the hatch, ladder and lighting, then load light seasonal items first and keep heavy boxes near load-bearing walls.
Tips and common mistakes
Never compress insulation to make room, because a thinner layer loses heat and can cause condensation.
Foam board carries no weight, so screws must reach the joists or the floor will flex under your feet.
Wear a dust mask and eye protection, and step only on joists or laid boards so you do not fall through the ceiling.
Keep soffit and ridge vents clear, or the roof deck can rot from trapped moisture.
Questions
Can I just screw plywood straight onto the joists?
You can, but it caps the insulation at joist depth, which is usually far less than R-49. That loses heat and can trap moisture against the cold roof deck.
How thick should the foam board be?
About 4 inches of rigid foam adds roughly R-20, which helps reach an R-49 target when combined with the insulation between the joists. Check your local code for the number in your climate.
Will the platform hold heavy boxes?
Only if the joists are strong enough. Spread the weight across several joists and keep heavy items near load-bearing walls.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
