We want to convert a screened porch to a more usable room. Will we encounter moisture problems due to the concrete floor?

Asked by Lisa Hills
Waupaca, WI

We live in northeast Wisconsin. We have a screened porch on the southwest corner of our house that we would like to convert to an all-season room. It is attached to the garage on the east side and the house on the north side. The floor is a solid concrete slab that has a basement underneath (the house has a walkout basement) but no insulation other than veneer brick on the outside. We would like to open the room up to the house and put a direct-vent fireplace on the wall connected to the garage. We would also like to put wood floors on top of the concrete in this room with nearly floor to ceiling windows on the south and west walls. We are concerned that we may encounter moisture issues either under the new wood floor or in the basement ceiling underneath this room. Do you think it is an issue and/or do you foresee any other issues we could encounter and how would we go about addressing them? Should we insulate between the brick veneer and the concrete floor? Many thanks!


Lisa, If the basement below the existing screen porch is condition by means of forced air heating and cooling system or radiators, once the room is enclosed above you will not experience moisture. I would recommend that you install a vapor barrier below the new wood floor as well as using pressure treated lumber which comes in contact with concrete (per code) if space allows. As for the insulating behind the brick veneer, I would not recommend this. Brick as well as the mortar are porous and wick moisture. The air space behind the brick allows moisture to drain out through weep holes typically placed at the bottom of wall.

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