My wife and I are building a new home this summer. One of the requirements is a dedicated shop rather than having in in the garage or basement of our house.

I've been talking to the general contractor who has suggested using prestressed concrete planks for the garage floor. This would create a basement under the garage that could be used for my shop. He said he's done it for other people.

Pro:

  • He says it costs less and requires less maintenance than an accessory building. (no roof, siding, etc.)
  • The county where I live restricts accessory buildings to 750 sq. ft. I will have a 3-car attached garage that is nearly 800 sq. ft. The SWMBO is unlikely to allow me to build a 750 Sq. Ft. shop. My shop is already bigger than the max I could have as a separate structure.
  • I can have heat, electricity and water more easily than I could in a separate structure.
  • I can heat the space with hydronic heat in the concrete floor as I plan to do with the basement in the house simply by adding another zone.
  • Because the shop will be below-grade, it will stay cooler in the summer.

Concerns:
  • Lighting: There will be few if any windows so natural light will be poor.
  • Ventilation: I don't want the shop connected to the air-handling system from the house to avoid dust, fumes and noise making their way into our home. How do I bring fresh air into the space without freezing in the winter?
  • Noise: The walls, floor and ceiling will be concrete. I'm told that unless the walls are covered with some sort of noise-dampening material, the space is very noisy. (Imagine running a tablesaw in a cave.)
  • Moisture: I'm concerned that moisture will damage my tools. Will I need to purchase and run a dehumidifier?
  • Getting items in and out of this space will not be as convenient as would a traditional garage-type structure. I am not planning to put a garage door on the space. I was thinking about a 6 foot wide opening with double doors.
  • I was concerned about having a low ceiling that would make handling sheet goods a pain. He said they'll just dig the basement deeper.




Here are some pictures of a house under contruction: (not mine)




I'd be interested in your thoughts and ideas on this. Do any of you have a shop like this or know of someone who has done this?

-Kevin