Garage monolithic slab drainage and insulation
user-7559714
| Posted in General Questions on
Im building a 36×48 garage. I have a monolithic slab that is 6” deep and the footer is 14” thick by 24” wide. I dont have a clear answer on where to put the perimeter french drain. Some show it below the bottom edge of the slab and other show it level with the bottom edge. Im in upstate ny along the canadien border. My winters get pretty cold. Should i also put perimeter insulaition and wing insulation around the slab? Will insulation work if it is not heated?
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Replies
Generally a garage floor is expect to get wet from time to time when the door is open or a wet car enters. So the floor is sloped so the water harmlessly exits the garage under the door.
Generally the slab is separate from the footing and stands a few inches above the slab. With the footing being level and the slab sloped the gap varies from front to back. The advantage to this plan is the wood is a few inches above the slab and will stay dry when the floor is wet.
Most garages do not have foundation drains install unless they need to go around the garage to drain a basement footing.
Walta
This is what i was trying to accomplish https://www.youtube.com/watch?v=RNVU1m9apf4
User...714,
There are two types of FPSFs. One needs the building above to be heated to avoid damage, the other uses more insulation to keep the ground warm. Here is a link to the guide:
https://www.homeinnovation.com/~/media/Files/Reports/Revised-Builders-Guide-to-Frost-Protected-Shallow-Foundations.pdf
As Walter said, the problem with garages built on monolithic slabs is that if you slope them the bottom plate is often in the drainage path of any water on the garage floor. It also means you have to cut each stud to make the top plates level. One alternative is to keep the perimeter of the slab level, and slope the interior to a floor drain.
Hey user....
Google frost protected shallow slab. You'll find some design guidelines there which discuss the wing insulation in various climates. I believe the purpose of wing insulation is help prevent frost heave. Probably worth the effort since your frost line is probably pretty low.
For your drain, I suggest having the lowest point of the drain at the same level as the lowest point of your foundation. Don't have to split hairs there on depth, but the ideal here is to prevent water from pooling against the concrete.
Jamie