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Question DetailsAsked on 4/27/2014

Should insulation under a 3 season room floor be covered on the side facing the ground?

We just had a 3 season room built in place of our deck. Our contractor originally said he'd add some lattice work between the bottom of the house and the ground but later said there was not enough space to work it in. I looked under there today to see if I could come up with an idea for closing the gap to animals and debris. I was really surprised to see all the brand new insulation completely exposed to the elements. Is this standard? Won't the insulation get ruined in our new england weather or by critters?

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6 Answers


It almost does not matter but what type of insulation was used. If it was fiberglass insulation some sort of support and vermin blockage should have been installed in my opinion and even if it was ridgid insulation such as foam I would have put in some sort of protection from animals. There is a fine line between what is code and what is good building sense. Was this room built on the existing deck or was a new one built. If on existing this should have been factored in and if new it shoud have been even easier to do as it was being built. In the New England area you have to factor in just as I do here in NJ that mice and other critters look for a warm place to winter over and I would probable have used rat wire under the floor to protect the insulation from those looking for a warmer place for the winter. Even if you can not crawl under the floor joists you can install it if you are creative. It would not be that hard to bend 14.5 inch pieces and nail to the sides and never have to crawl under the deck and if it is a new deck it would be even easier to plan for it.

Good Luck Don

Answered 6 years ago by ContractorDon


Thank you for your response, Contractor Don. To answer your questions: The room is new construction on footings- The old deck was completely removed. The insulation is not blown in- We originally requested that but the contractor said the didn't have enough room to do that so we settled for the fiberglass. Any thoughts on what we can do now?

Answered 6 years ago by Ace


I hope you have enough room to crawl under there - for inspection, repairs, and cleaning out any accumulated debris. Code requires 18 inches between untreated joists or flooring and the ground for your case (8 inches for open decks on concrete posts or piers). If he said he could not fit in lattice, sounds like you may not be up to code for clearance underneath anyway, because 18" plus height of rim joist is plenty of room to install lattice.

Because this is a "room" then the code applies with respect to insect and vermin control. What he should have done is put high permeability housewrap - like Tyvek housewrap, NOT roof "waterproof"membrane, across the bottom of the joists, sealed tightly all around against bug entry. Normally that goes on first as soon as joists are in, then the insulation is put in from above, then the decking/flooring, for new construction. That would keep bugs out, dramatically cut down on drafts (unless he put a vapor barrier right under the floor), and protect the insulation from the weather. In situations where there is a possibility of water coming through from above, then instead of housewrap a tightly woven synthetic geotextile or metal window screening called "bug proof" - finer openignthat keeps ants and such out - is sometimes used, as it will let water flow through - but also allows more airflow so can be draftier through floor, though over open airjoists sheathing should have been caulked at the joints.

For rodents and snakes and such that might work or chew their way through the wrap, the perimeter of the construction should have a relatively fine mesh (1/4 inch opening or less) like galvanized hardware cloth or metal window screening (though that is less resistant to raking damage) nailed or 9/16" stapled at very close spacing to the back sides of the rim joists (for appearance sakes - doing it now may probably be on the bottom or outside of the joists) all around the room and embedded at least 6 inches in the ground, with ALL possible openings in it and where is meets up to house and room blocked off with wire mesh or with steel wool stuffed in openings (rodents won't chew through that) and caulked in, and seams in the mesh being lap jointed between screwed together pieces of treated wood, or lap jointed stapled tightly and very closely spaced to a treated backer strip of wood at least 3/4" thick to eliminate any openings at the joints - best to put in vertical pieces of copper treated 2x4 embedded in the ground and nailed to the rim joists, or make sure all end lap joints occur at posts you can staple to. There should be a hatch or accessway to allow access for inspection and any needed termite treatment - though hopefully your posts were concrete or ground-contact copper treated wood.

The wire mesh should stop chewing and slithering critters, and keep most blowing debris from accumulating under there, while still allowing ventilation to prevent excess moisture buildup which can occur if you put on treated plywood skirting, like on permanent trailer home installations. Keep clear with leaf blower blowing along the face rather than toward the mesh, so ensure ventilation and reducethe amount of leaf debris that gets through.

If your floor joists are closer than 18 inches to the ground, I would recommend highly (taking into consideration child and pet issues) either spreading granule insect poison aroundthe bottom of the screening annually, or if pet/child issues exist, spraying foundation perimeter insecticide inside the bottom of the screening annually, to cut down on the incidence of insects breeding under your room.

On the insulation - beglad you got fiberglass rather than blown-in cellulose - that would violate code in an open ground exposed environment, and would be expected to pick up moisture rapidly and start mildewing, same as it does in attics.

Answered 6 years ago by LCD


Was this job done with a permit? If so I might be inclined to talk to your Building Official. As LCD said this addition, which is what it really is does not seem to meet code. I would hope the floor joist system is treated lumber as this is way to close to the ground. LCD said code is 18 inches on the West Coast for rooms, here on the East Coast it is 30 inches as that seems to be the point that termites can not build the self supporting tubes from the ground. We have to have at least 8 inches of exposed foundation to the ground to watch for the tubes they build on the surface of the foundation wall. If left exposed it will shortly become an unisulated floor with all the critters stealing materials for their nests and hopefully they will be nice enough to use your floor as a building supply store and not the location for the home.

If the job was done without a permit I would still go to the town inspector and ask what he thinks. As a homeowner you could play dumb and say you did not know you needed it for a seasonal room or bend the truth and say you thought contractor got it. Before you do that you might call the contractor to let him know you are going to turn him in and he might come up with a solution. I think many if not most contractors have done jobs without permits but when it is done all the T's should be crossed and I's dotted. And if done it should be to code or even better.


Answered 6 years ago by ContractorDon


This project was done with a building permit. Interim inspections have been done- The final inspection has not- I am hoping to meet with the town's building inspector tomorrow. I regret that I have made full payment in advance of the final inspection. I now wish I had made the final inspection a condition for the final check. I can only hope the contractor is honorable enough to make things right. I guess my best hope is to have this fail the final inspection.

Thanks again for your input.


Answered 6 years ago by Ace


Oh yeah, NEVER make final payment until the full punch list is completed AND you have lien releases in hand from suppliers, subcontractors, and general contractor.

On other thing on the distance off ground issue - one of the other comments talked about exposed wood haveing to be 30 inches off ground back east. The 18 inch distance I gave is from the International Residential building code, which is used in most states. Certainly, different states and localities have local amendments to the general building code, so can vary from place to place. I ran into one today doing another comment where they adhered to 8 inches from grade for untreated wood which is really risky, and in Hawaii it is 18" clearance on beams and 24" on floor joists though they have to be treated against termites, so clearly varies from place to place.

BTW - crawl space access hatch - whcih should also be insect proof, should generally be not less than 18" high x 24" wide open area.

Certainly talk to the inspector, bring out your concerns. Assuming he fails it, then time to talk to contractor about fixing it right.

If he refuses, based on a failed inspection, you can contact his bonding company about bringing it up to snuff.

You can also contact the city/county business license agency with a failed inspection and any other pertinent correspondence and see about having his business license revoked. Ditto with state licensing board for action against his contractor's license (also city contractor's license in some areas). - Those sort of action will certainly get his attention.

Other options include of course Angie's List dispute resolution service, and as a final resort an attorney to sue or suing in small claims court, and after all is said and done, an appropriate AL review.

Answered 6 years ago by LCD

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