How do I winterize crawlspace under closed-in porch?

PLa23647394
by PLa23647394

What is the best way to winterize a crawlspace under a closed-in porch which now serves as a bathroom?I have an old building with a brick and stone foundation. The old porch has been closed in with windows, but underneath it there is no foundation. There are just posts with lattice between them which leaves it open to cold weather and moisture etc. The floor is just dirt, and there is no opening in the foundation to the crawlspace.I am remodeling the building. I would like to use the space above the crawlspace as a "half" bathroom with a drain in the middle of the floor, and the wall mounted toilet and sink lined up against the wall of the exterior wall of the building (i.e. the interior wall of the old porch), and draining down into the basement of the actual building (inside the foundation). Thus, the only plumbing item in the crawlspace would be the floor drain with the tile floor sloping toward the drain. How do I keep this drain from freezing and how do I try to keep the heat from escaping into the crawlspace. I have done some research on-line and it seems that there are two ways of approaching the problem. Insulating and closing in the bottom of the bathroom floor over the crawlspace, and the other closing in the walls and floor of crawlspace to make it water and air tight. I am anxious to hear what the experts will suggest is the best way to accomplish my purpose. Thank you.

Above the lattice in the picture is what was originally a porch that has been closed in with walls and windows. The lattice is open to the air, and there is a dirt floor in the crawlspace. There is no window or other opening in the foundation wall into the crawlspace.

  4 answers
  • Jcraw Jcraw on Aug 30, 2018

    We had the crawl space insulated under ours.

    They spray-foamed and covered that with insulating foam-board under the floor. Foam- board was applied to all the walls.


    We installed an 18” deep IKEA sink vanity where the plumbing is in the wall (gives you full. depth drawer storage). They foamed the whole new bathroom but also put some foam-board behind that plumbing.

  • William William on Aug 30, 2018

    I would do both. Insulate the bottom of the floor, close and insulate the walls of the crawl space. Lay some plastic sheathing over the floor.

  • Eloise Eloise on Aug 31, 2018

    Not sure you'll get all the answers you seek, but here's a start: https://www.youtube.com/results?search_query=how+to+winterize+a+crawl+space

  • Virgie Jaquess Virgie Jaquess on Nov 25, 2018

    laying plastic sheeting on the floor is the first step and goes a long way for insulation. Use foam boards behind the lattice. Staple in place or use waterproof gorilla tape.