QA: Missing Fasteners and Flipping Insulation

We are replacing carpets in our home built in 2018 and I noticed that in one of our rooms there is a subfloor sheet right in the middle of the room that only has fasteners at the perimeter. There are no fasteners in inside of the board (all the other sheets have fasteners at the perimeter and inside the sheet spaced at the 16″ interval and spaced 12″ away from each other). Any idea why they didn’t install fasteners in the middle of this one sheet?

Simple construction error is the most likely reason why you did not find any field fasteners in one floor sheathing panel. The new guy was put in charge of screwing down the floor sheathing and got a little too caught up listening to NPR. Or they ran short on fasteners and forgot to come back to it. The inspector took a look at the other rooms and fastener spacing looked good, so only did a quick glance into the one with the problem. It happens.

Before you install the new carpet, you might as well fix the issue. Unless you are skilled with a hammer or own a framing nailer I would recommend using screws because most homeowners have a battery-operated impact driver or know where to borrow one. Here’s the rub though – the 2015 International Residential Code does not list any screws in their nailing pattern table, only nails.

We are in luck though, because the hardware company Simpson has a sheathing screw that they have put through testing with the International Code Council Evaluation Service as a sheathing nail replacement. The ICC-ES Evaluation Report for this screw is ESR-1472 (ver. 9/2020) and states “The [Simpson] WSNTL and minimum 2-inch-long [Simpson] WSC screws may be used as substitutes for the 8d and 10d common nails prescribed…in Items 30 through 32…of 2018 and 2015 IRC Table R602.3(1) (similar in earlier code editions) for the attachment of subflooring to framing; provided the penetration into the framing members is a minimum of 1-3/8 inches”. Items 30-32 are the floor sheathing lines of the IRC table.

The Simpson WSNTL screw is available as a loose screw, perfect for homeowners and repairs. The Simpson WSC screw is a collated screw used with a dedicated tool. If neither of these are available in your area, take a look at the specification for these screws and you should be able to identify a local alternative.

One final note – the edges of the floor sheathing where it rests on the joists should have a six inch fastener spacing, not twelve inch. It is not the end of the world, but if you have some screws left over you might want to sink them on the edges to create a six inch spacing. This pattern is found in the 2015 International Residential Code Table 602.3(1) which states “spacing of fasteners on floor sheathing panel edges applies to panel edges supported by framing members” which, in this case, is a six inch spacing. Your local code may vary.

My inspector noted that some of the insulation in my attic was installed upside down. It is fiberglass insulation with paper on one side installed in the floor of the attic. The paper is on the top side of the insulation. Can I just flip the insulation over to fix this issue?

This fiberglass insulation is known as ‘kraft-faced’ fiberglass insulation. It has paper attached to one side of the fiberglass to aid installation (this paper can be fastened to framing members to keep the insulation in place) while also acting as a vapor retarder which helps limit the amount of moisture migrating into the wall or ceiling.

This kraft paper layer should be installed on the ‘warm in winter’ side of the wall or ceiling because, in heating climates (Climate Zones 5-8 and Marine 4), that is where you want to have the vapor retarder (IRC2015 R702.7). You have warm air inside the house full of moisture and you want to prevent it from getting into your wall or ceiling. Kraft paper installed on the ‘cold in winter’ side just isn’t being given the opportunity to perform properly. This is why your inspector probably flagged the insulation as being installed upside down.

If the insulation can be easily flipped, go for it. It can only help the performance of the attic floor from a vapor perspective. You will also be protecting the kraft paper which, when facing into the open attic, can pose a danger if there is a house fire. It’s just a layer of paper, but minimizing fire risk is a cumulative project. You won’t find this fire risk directly called out in building codes, it is usually part of the manufacturer’s installation guidelines. For more details, check out the North American Insulation Manufacturers Association (NAIMA)’s publication BI402 which covers installation techniques for fiberglass insulation. It recommends that the kraft paper be installed with substantial contact against drywall.

If the insulation cannot easily be flipped you can usually tear the kraft paper off from the visible side pretty easily. This won’t fix your vapor retarder, but it will address the fire risk.