Primarily Petroliana Shop Talk Forums Non-Petro Discussions Non-petro Discussion and Showcase Different kind of ? about mice in garage.

I live along the edge of a wooded area and I have had mice in the garage. I removed anything and everything that they may want to live in and all materials that they may want to build a home with, and a little help from Decon, and since have had no problems.
So I have your typical wook framed construction garage with 2 x 4 walls and 2 x 8 roof rafters with 3/4" plywood roof sheeting. I've never seen it done before, but I want to insulate the ceiling space between the 2 x 8 rafters and then enclose the space, or install a ceiling of 1/4" plywood. I'm pretty sure I can enclose things quite tightly, but mice can get into almost anything if they really want to.
So here is my question. Are mice going to get into the space and set up camp? Is there any reason to believe that they would invade this space any more than they would or could the walls?
Your thoughts?
And to the construction guys out there, what, if any kind of venting would need to be added if I enclose this space?

Steve:

Mice don't care about insulation. They will build nests in it and drag it anywhere they want. I've had mounds of it behind cabinets against the wall at the floor level.

BTW - you don't want to fill the area in your illustration with insulation. Your roof needs to 'breath' and the vents in your soffits allow air to move up the inside of your roof and remove heat and moisture.

Blocking this area off with insulation will cause mold and rot to the inside of your roof structure.

They make 'baffles' that go into that area and attach to the underside of the roof. The insulation goes 'below' the baffles and across the ceiling joists - not the underside of the roof itself. The baffles allow the movement of the air.

If it was me, I'd do a plywood floor in the attic over the insulation with a drop down ladder for extra storage. Then sheath the ceiling with plywood or similar material.

Sheetrock is inexpensive and easy to paint - but it can crack along the taped seams in a garage as they have a tendency to move around in the wind more so than a house.

Later . . .

Jim

If you fully insulate between the rafters as shown, you will have no ventilation and the heat/moisture buildup will destroy the roof. Vaulted ceilings are nice but you need to frame up one a bit below what your structure wood work is. Thereby eliminating the venting problem. At the eve, where the wall joins the roof line, a hopper vent tube must be installed to keep insulation from closing off the vented area. Common sense stuff. Mice are always a problem. Get a cat. Paul www.severngaspumps.com

Jim,
that is exactly what I was wondering about. I remember in an old house I had, we added a room with a cathedral ceiling and I remember installing these blue foam like vents that attached to the bottom of the roof sheeting. So I know what your talking about. And I was wondering if this was needed in a garage. And from what your saying that would be a yes. But in my old house there was a ridge vent in the roof and soffit vents along the bottom. Allowing for good air flow. My garage does not have a ridge vent. It has 2 metal type roof vents which i was going to box out so that they still vented to the actual room space.
I do not want to enclose the space at the joists. I dont want to loose that ceiling space for sign display. And because of the low roof angle, I would not have access to most of the created space. It would only be useful in the very center of the structure.

Using the two metal vents to move air out of the actual room space will do nothing to keep the roof dry and cool. If you had designed the roof to be somewhat higher, you would have had the needed space to put in the false roof vault. Unfortunately, this problem has no easy answer. Over time, an unvented roof will decay. I'd forgo the idea to fully insulate the roof rafters, with fiberglass insulation. You might give some thought to using 1" foam held to the bottom edge of the rafters, allowing the air above to be vented? Not the perfect answer but one that will help if done correctly. Paul www.severngaspumps.com

Soffit vents- baffles- then install a ridge vent.The ridge vent is pretty easy-tear off your caps, saw a slot the length of the roof at the peak and install the vent and new cap.

I have quite a bit of knowledge of roof venting in the northeast where ice dams are more of a concern, but you still need to vent properly in your climate.
By far the easiest solution would be to install ceiling/floor joists and insulate between them, then sheetrock. Venting would not be a major concern, but I would add gable vents to pull in outside air. If you want to do the cathedral ceiling, you need to install the Styrofoam baffle (called proper vent around here)the entire length of the bay and add soffit vents and a ridge vent. If you have any hips and valleys that will not be vented by the soffit and ridge vents, drill 1 1/4" holes along the rafter so it vents into the adjoining bay.
If mice can get in your garage, then they will get into insulated rafters. Insulation doesn't bother them, so seal all possible entry points and don't forget the seal under your overhead door where they commonly get in in an otherwise new sealed building. Good luck!

Sure Cure

Okay, So ridge vent, soffit venting and baffles it is. I see no way of heating the garage all winter without some kind of insulated ceiling. It would cost a fortune otherwise. My goal is to create a nice clean year round space.

I'm getting what you are all saying and I'm glad I asked. The roof must be vented.
This is a picture when I had just finished the process of enclosing the car port protion of the structure. As you can see, it is a hip roof with only 6'-7' ridge along the top. But I think I'm understanding that all cavities have to have air access to the ridge vent. Looks like I'll have to drill quite a few holes.

Thanks all for the help!! As for the possible mice? I'll just have to stay on top of it I guess.

Mice are very thankfull for the up garage door. Takes all the guess work out of how to get in.LOL!

I use stuff in pellet form called One Bite for my mouse problem. Seems to do the job quite well.

Steve:

If you really want the shop to be warm in the winter, insulate all the walls and the rafters and install finished walls and a ceiling. Paint it all then move in your collection.

I personally like the look of a museum layout instead of a bunch of stuff up against open walls with the studs showing. Spend a bit of money now and you will have a much nicer display area forever.

Later . . .

Jim

Steve, they recommend a lot of insulation for attics and ceilings in our area-like R50 or R60. You will have a real tough time achieving that with a vaulted ceiling. I'm not sure but I think it would be like 18-24" of fiberglass. Our first house was a bungalow and I finished the attic. The roof rafters were only 2x6s as I remember and were already sagging quite badly. I solved both problems (no room for insulation and the sag) by reinforced them by screwing I think 12" high 1/2" plywood alongside them with a 2x2 screwed to the bottom for something to screw the drywall to. I started on each end then strung lines to fill the rafters in so the ceiling would come out in a nice plane. I couldn't go any more because there was only so much headroom.You have to be patient and meticulous with the insulation. With the shingles, plywood, fiberglass, visqueen VB, and drywall I'm sure I probably only got R35 or 40 but it was always comfortable and our heating bills went way down because there was very little original insulation in the floor.

Wow Jim, that sounds like a lot of work. Far more then I would be willing to do for a garage.
My cousin has the same basic garage but he put in blown insulation. Which to me looked like hell!! I could never stand to look at that. But he said it allowed him to keep it a constant 60 deg during the winter months and his bill only went up like $20 a month. And when he went out there, he just turned the heat up a bit. That is all I'm looking for.
I wonder at what temp difference does condensation begin? I mean if you keep it at 50 or 45, and then turn it up to 70, will condensation form? Hmm...

My plan is to install all the venting and insulate it as best possible and put a 1/4 or 3/8 ceiling in and paint it all white.
I'm hoping I can seal the space everywhere well enough that should any mice show up, they can't get into the cavity.

DB, that unset trap isn't going to catch anything!