Gap Between Ground & Floor of New Addition


Question: My wife and I are in the middle of building a sunroom, and we’re trying to figure out how much clearance we need between the ground and the floor of the sunroom. The sunroom itself is four seasons, and the floor will be insulated. It rests upon several helical piles.

Currently, there is about an 18″ drop off in our yard from one corner of the sunroom to the other. It’s dug out quite a bit right now, so there’s lots of air flow. But obviously, having a big gap between our yard and the sunroom isn’t great.

We’re thinking of doing one of two things. One is pushing back the yard and building a retaining wall with a sunken patio. This would allow for maximal air flow, but would be costly and would take up more of our yard.

Another option is to grade the yard up toward the sunroom, but still leave about 6″ of clearance. That would still provide air flow, but is it enough to ovoid moisture and rot long term?

Thanks for any help you might be able to give!

Answer:

Personally I would not spend the additional money to slope the yard, add the retaining structure and build a dropped patio. Moisture develops when humid warm air is in contact with a colder surface and there is condensation without adequate venting. That being said, maximize the space between the floor and the top of the stone, having the stone inplace is perfect for reducing any accumulation of water under the sunporch. If you can maintain the 6″ I would think that you will not be promoting mold or lack of ventilation moisture buildup. The other thing to make sure of is the placement of the vapor barrier. The vapor barrier should always be towards the conditioned side of the space. You do not want to trap any moisture within the insulation and or the sheathing. This is why we place batt insulation with a vapor barrier with the fiberglass towards the exterior and the vapor barrier, foil or paper towards the interior of the home. In the basement application the vapor barrier would go up and not down towards the basement. Conditioned space should dictate the positioning of the barrier. I would also use a synthetic underlayment in the room to minimize any deterioration due to moisture. The new synthetic underlayments are designed to reduce retention of moisture and I would spend the additional few dollars on a good underlayment.

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