8 Common Sub-Floor Installation Mistakes

Flooring is only as good as the sub-flooring supporting it. If the sub-flooring is not dry enough or hasn’t been properly cleaned a variety of issues can arise, causing homeowner complaints and callbacks. 

Here are eight common sub-floor installation mistakes that can promote a variety of problems, including mold:

1. Improper spacing between panels: Most manufacturers recommend 1/8 inches (1/16 inches for some premium sub-floors) at panel ends and edges. 
2. Upside-down installation: In all cases, the detailed panel trademark stamp should be installed downward so it can be examined during inspections.
3. Improper fastener placement: Be sure to place all perimeter fasteners 3/8 inches back from the nearest panel edge. Use this guide:
   • From corner panel: 3/8 inches
   • On-center along panel edges: 6 inches
   • On-center along center supports: 12 inches
4. Not gluing properly: For best results, don’t glue too far ahead. Work no more than one panel ahead. Also, apply a small bead of glue in the tongue-and-groove to significantly help reduce any movement and noise. 
5. Delaying fastening: Fasten each panel fully as you go to ensure full adhesion and avoid movement and noise down the road. 
6. Using improper fasteners: Using code-approved screws rather than nails is the best option for avoiding movement.
7. Letting water sit: If the floor system is exposed to the elements and bulk water is present, sweep it off or drill drainage holes.
8. Improper storage: Always store panels in a clean, dry area and off the ground. If stored outside, cover panels with plastic sheets or tarps. Keep the cover open and away from the sides and bottom of the panels to allow for air circulation.

If you have consistent issues with moisture in your sub-flooring—especially if it’s causing significant problems for the floors above­­—it may be time to test different premium sub-flooring products. LP Legacy^® Premium Sub-Flooring uses panels that are packed with more strands, resin and wax to provide exceptional resistance to moisture and edge swell to help improve flooring performance. Additionally, the water-resistant resins use Gorilla Glue Technology^® for exceptional stiffness. In fact, it’s so strong that LP offers a unique Covered Until It’s Covered^® no-sand warranty with a lifetime limited warranty that lasts as long as the home.

To see the correct way to install LP sub-flooring, check out this video with contracting professionals Jordan Smith, chief builder and owner at Smith House Company, and Kyle Stumpenhorst, owner and contractor at RR Buildings. For in-depth information on sub-flooring, check out the blog article, A Deeper Look at Sub-Flooring.