Is it okay to put plywood over insulation in an attic?

Author: Rae Hackett  |  Last update: Tuesday, February 11, 2025

Can I put plywood over insulation in the attic? Yes you can install plywood subflooring directly over the floor joists and insulation on your floor. You need to install rigid insulation boards on top of the attic flooring joists and then install plywood over the top.

Can I put plywood over attic insulation?

Hey there! 🙌 Yeah, you can totally put plywood planks on top of your insulation in the attic. Just make sure it's not compressing the insulation too much, ya know? 😅 You want to keep that air flow going and not mess up the R-value.

Can you put boards over insulation in an attic?

When you're ready to install your loft boards, you should position them above your insulation using Loft Leg supports designed for this purpose. This will avoid compressing the insulation and ensure it is working to its maximum potential.

How can I cover exposed insulation in my attic?

The good solution for this is a house wrap material (often referred to by the popular commercial brand Tyvek) which allows vapor to pass through while blocking water itself on the outside of the home. You can also put up a thin board, plywood, or even drywall, if the goal is simply to prevent accidental contact.

Does plywood help with insulation?

Plywood will assist with insulation by reducing the effects of cold and heat, while drywall reduces sound. Suggestion: You can combine the two to get the best results.

Installing attic floor over insulation

What to put over insulation?

Installing foil on top of the insulation acts like the windproof shell on a jacket. The SuperPerf foil helps minimize convective looping within the insulation.

Does heat damage plywood?

Exposure to Extreme Heat

At temperatures above 200° F, plywood undergoes slow thermal decomposition that permanently reduces its strength.

Should insulation be covered in attic?

Attic Floor Insulation

Unfinished or uninsulated attics need a layer of protection to keep hot or cold air from migrating to the rest of your home. The material should be faced if you install batting between your attic floor joists.

Can you put stuff on top of insulation?

Boarding over your loft insulation can be a great upgrade for your home when done correctly, so your insulation is not compromised. It can provide you with usable storage, or even extra living space, which will only enhance the value of your property.

Is it possible to over insulate an attic?

Yes, it is possible to put too much insulation in a loft or attic.

Can you put a vapor barrier over insulation in attic?

In colder climates, where the home's heating system sees more use, the vapor barrier should typically be installed on the insulation's interior side. In warmer climates, where the home is often kept cooler, the vapor barrier should usually be installed on the exterior side.

Can I put foam board over insulation?

Yes, foam board insulation is an excellent complement to batt insulation. Foam board insulation can add insulation and eliminate thermal bridging when used in wall and ceiling assemblies insulated with batts. It can potentially replace the vapor barrier and house wrap as well.

Does squashing insulation stop it from working?

Squashing your insulation reduces its effectiveness by 50%

Numerous studies on the topic have indicated that there's a huge number of Britons who don't understand why doing this is so problematic. Mineral wool type insulation (the most common loft insulation) needs to retain its full depth in order to work effectively.

How thick should plywood be in attic?

Meanwhile, 3/4 plywood for attic floor is the recommended dimension regardless of the joist centre measurements and weight requirements. While 1/2 plywood is cheap, the support of 3/4 plywood floors gives long-term cost savings by preventing premature damage.

Why is the plywood in my attic wet?

In the winter, attic condensation often turns into frost, which actually doesn't pose any threat. However, when the frost melts, it turns back into condensation, which makes everything it touches wet –usually insulation and wood.

Should attic insulation cover joists?

In unfinished attic spaces, insulate between and over the floor joists to seal off living spaces below.

Can you board over insulation?

Boards for loft flooring can be installed on top of insulation using plywood, wood, or plastics. Installing loft flooring and boarding over insulation helps save space, prevent heat loss, and increase home value.

What can I put over insulation?

What can I use as a vapor barrier?
  1. Elastomeric coatings.
  2. Aluminum foil.
  3. Paper-backed aluminum.
  4. Polyethylene plastic sheet.
  5. Asphalt-coated Kraft paper.
  6. Metallized film.
  7. Vapor retarder paints.
  8. Extruded polystyrene or foil-faced foam board insulation.

Can you store stuff in an attic on insulation?

Insulating your attic makes it more energy efficient and can help regulate the temperature, making it more suitable for storage.

How many inches of insulation should be in an attic?

If you live in the Southern part of the U.S., the recommended insulation level is a minimum of R-38 or about 13-14 inches of insulation. If you live in the Northern part of the U.S., the recommended insulation level is a minimum of R-49 or about 16-18 inches of insulation.

Can you put Tyvek over insulation?

Yes. DuPont Tyvek® is compatible, and can be installed with foam insulation products.

How do you tell if your attic is properly insulated?

Looking across your attic, if the insulation is level with or below the attic floor joists, you probably need to add more insulation. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough, and adding more insulation may not be cost-effective.

Does plywood help insulate?

On the one hand, plywood does have high thermal and sound insulation. This makes it a useful insulating material for flooring, ceilings, roofing, and wall cladding. Ultimately, the insulation properties offered by plywood can dramatically reduce heating and cooling costs, which is excellent for your wallet.

At what temperature will plywood catch fire?

What Is the Ignition Temperature of Wood? Wood placed in an oven at 700°F. catches fire almost immediately. At oven temperatures of 450°-500°F., the wood gradually chars and usually ignites after several hours.

What is plywood not good for?

Using Plywood may sometimes be difficult. While some kinds of plywood are suitable for outdoor use, plywood is susceptible to moisture and can warp, swell, or delaminate when exposed to water or high humidity. This is the main disadvantage of plywood.

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