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Can I nail attic floorboards directly onto the joists, or do I need to use spacers?
Anonymous user 08/10/2025 - 2:04 PM
We've got an attic that's partially floored, and it seems like the previous owner nailed the boards directly onto the joists instead of using spacers. We're considering completing the flooring, but we're not sure if we should remove the old boards and redo everything with spacers. I've heard that the height of the insulation might be an issue, but I'm also concerned that installing boards directly on the joists could cause moisture problems. Any advice?
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4 Answers
Reg Bell Construction
No reviews yet
Air need to be moving in your attic at all times and if you are able to put boards down in that space you likely do not have enough insulation in Your attic.
However that will not create mold on it own there would be other factors like poor ventilation...not enough soffit or roof vents is a major cause of mold.
Answered1 October 2025
0
Nadraha construction services Inc.
Rating: 4 out of 5
If the boards are nailed directly onto the joists, there’s no ventilation gap, and that can trap moisture and compress insulation, reducing energy efficiency.
Best practice:
Remove the old boards.
Add loft legs or spacers (at least 4–6 inches above joists) to keep the new floor clear of insulation.
Lay rigid boards or plywood over the spacers, leaving small expansion gaps between sheets.
That way, the attic stays well-insulated, ventilated, and dry, and you won’t risk condensation or mold buildup under the floor.
Answered6 October 2025
0
Total Reno & Design
Rating: 5 out of 5
You can screw or nail down boards providing that there is adequate air flow. You should have roof vents that should be visible when you look up at the roof from either inside or outside. More importantly you need to have proper soffit vents. If you cannot locate the soffit vents, you might want to get a professional to investigate if you have the proper amount per square foot of space.
Answered7 October 2025
0
AKAHGODWIN
No reviews yet
Well, I won’t support the idea of nailing the floorboard because it’s going to prevent the smooth flow of air around the attic and this may cause Mold because of moisture trap. It can also affect the energy-efficiency thereby causing you more money to generate adequate heat.
Answered8 October 2025
0