# Insulating detached garage shop



## nickajeglin (Jul 14, 2019)

Hello everyone, I recently bought a house and I'm planning on moving my woodworking shop from my parent's basement to the detached garage. The only problem is that it's unbearably hot.

I'm wondering the best way to insulate and heat/cool it enough to work out there. It's a sloped roof with no soffits. 
I did a little research, so I feel pretty confident that the walls aren't too hard. I would just put 2×4 framing right up on the cinder block, roll out fiberglass between the studs, and nail on drywall, OSB, or plywood.

I'm more confused about how to handle the roof. I see two or 3 possible options:
1) Treat it exactly like the walls: roll out fiberglass, and cover it up. pros: I keep the wood storage in the rafters, high ceilings are nice cons: requires more sq. ft of insulation, I have no idea how to handle ventilation.
2) Build a ceiling, and insulate that from above pros: less insulation needed. cons: I lose the wood storage space and the ceiling is lowered.
3) Build a mini-ceiling about halfway up the roofline so I have a trapezoid shaped ceiling. pros: I keep some storage space, maybe ventilation is easier, it takes slightly less insulation material. cons: ?

With respect to heating and cooling, I don't need it to be 70F year round, just bearable. Like between 40 and 80. This makes me think that insulating the ceiling is probably enough, and then adding a window unit and space heater would probably do it.

From the small amount of research I've done and just general knowledge, I understand that ventilation is super important when it comes to the roof, but I don't really know the best way to approach this since there aren't any soffits to place vents in.

Can someone with more experience point me in the right direction? Especially when it comes to how to correctly provide air flow for the roof. I'm leaning towards option 3 right now, as keeping the wood storage is pretty important to me, and it seems like it might make ventilation easier.

I uploaded some pictures here

(This is crossposted from the homerefurbers forum as it doesn't seem quite as active as this one.)


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## PaulDoug (Sep 26, 2013)

The walls look like they are block, so shouldn't need a lot of insulation, if any to keep it "bearable" so I would concentrate on the ceiling. Might check on what it would cost to have sprayed on insulation sprayed on it. Or get rolls of insulation and staple it in place, then cover with drywall. Looks like 2×6 or 8 boards up there. I'd make sure it can support the drywall/insulation. I am do expert, so maybe ask some local experts. The roof doesn't look like it was built to handle a lot of weight, maybe have to beef it up some. Don't know were you live, do you have to worry about snow weight?


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## rwe2156 (May 7, 2014)

90% of your heat gain is from the roof. In the winter, the walls will work against you.

For now, I wouldn't insulate the walls. I would install a ceiling (2×6 joints) and R19. Plywood or sheet rock for the ceiling. There are other options such as rigid foil coated sheets. Not sure about applying right next to wood.

That said, my first choice would be spray foam applied directly to the bottom of the roof. Its such a small job you may have trouble getting it done. There are place that will rent a foam machine. Factor the coast against all the carpentry, insulation, soffits and time.


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## Hammerthumb (Dec 28, 2012)

You could re-roof with an insulated roof. Foam on top of existing sheeting, another layer of sheeting on top of foam, then a new roof.


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## Knockonit (Nov 5, 2017)

for the walls, look into foam with furring strips in it for attachment and for ext wall finish, foam is a better insulator than batts on block, and takes less room out of work space. pending where you are might consider a moisture barrier, since i live in the desert, we dont' worry much about it, but at one time did live in south bend in for a few years and the moisture there was troublesome
Rj in az


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## Delete (May 19, 2017)

I couldn't see your pictures so I probably shouldn't comment, but here is one idea you may want to adapt to your situation. Foam is nice but some prefer to avoid chemical formulas even if they are solidly approved. For smaller jobs fiber insulation (fiberglass, roxsol, etc.) can be easier and cheaper.

Your option #3 is probably the best of both worlds (high ceiling, low ceiling). Heres a quick sketch of how I do a ceiling like that. Condensation will reduce the efficiency of your insulation, air movement is important. Don't forget to include a vapor barrier between your insulation and interior wall finish.










Edit: There is an additional benefit to this method. You probably don't have problems with roof loads such as snow, but if you did or experience volatile weather, the triangulation of the roof rafters will greatly strengthen your roof assembly.


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## controlfreak (Jun 29, 2019)

Foam the roofline, it is by far the best way and would leave a higher ceiling for storage. I would not attempt to do foam yourself. The guys that do it usually have pressurised suits to keep the chemicals out of their eyes. They say everything takes on a rainbow tint after it hits your eyes. The walls you may be able to do slats with foam boards but you may want to watch the moisture level to prevent mold.


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## clin (Sep 3, 2015)

Moisture issues can be very specific to where you are located. I'd make sure to find out what best practices are in your area. Generally you want to do everything you can to seal the outside. But that is already done, well or not.

The general issue is water vapor passing through the insulation and condensing on cold walls or roof. This for example is why attics are often vented. Any moisture that gets up there has a place to go. There are ways to keep insulation off, but close to a roof and vent it. Usually through soffits (which you don't have). This is why spray foam can work so well. It seals and ensures no water vapor can reach it.

That said, I've also heard that moisture getting in from the outside tends to be the real issue, and the better sealed it is on the inside, just makes it hard for the moisture to dry. This brings me full circle to finding out what is best and common in your area. Often it is a compromise for what is best most of the time. And you'll need to factor in the details of how the existing structure has been built. What's best for a stud wall is probably not what is best for a block wall.

Bottom line, get some local expert advice. You don't want to create a rot or mold problem.

I also think there will be a way to insulate the roof without forming an attic and therefore make use of the overhead space for storage. I think you're making too much out of the added insulation. Unless the roof is abnormally steep, I doubt the roof area is that much more than the ceiling area.

On that note: Storing lots of wood can be heavy, make sure the roof structure can support that. If not, reinforce as necessary.


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## CaptainKlutz (Apr 23, 2014)

Hmm, lot of ways to do this?

Open soffit roof on block walls is old school way to build forging or metal fabrication work shop in 'mild' climates? 
Current building codes would require some changes to that roof structure. Looking at the roof boards, appears there are replacements, and some with old water damage?

So first: 
Suggest you call 3-4 roofing companies and get quotes/designs from them about best way to insulate and deal with that roof. Be sure to ask about any deficiencies in roof that would be upgraded as part of insulation work. This will give a solid direction on methods and costs involved.
Last thing you want to do is insulate the inside, and have leaks to learn you need a new roof. If need a new roof, then option to add reflective foam insulation boards under the sheeting/shingles will be great start to reducing the heat load and might leave you a more open attic area for storage.

+1 Use foam board on walls with furring strips.

+1 Must plan for moisture control.
Be sure to seal the inside of block with water proofing cement paint, and put a moisture barrier under the wall sheeting. Water goes right through block, and then acts sort of like a sponge. Water is always there, till it completely dries out. With painted outside surface slowing moisture transfer, completely dry block walls will never happen.

Best Luck.


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## therealSteveN (Oct 29, 2016)

> That said, my first choice would be spray foam applied directly to the bottom of the roof. Its such a small job you may have trouble getting it done. There are place that will rent a foam machine. Factor the coast against all the carpentry, insulation, soffits and time.
> 
> - Robert


I agree spray foam is going to be the most economical answer. A person can buy 2 tank mix systems that blow through a $50.00 handset. Not something you are going to go into business with, but for that 40 minute job, more than sufficient. Enough foam to do that is 600 bux, possibly less with the wonders of the innerweb. Add a few bux and you can do the walls. The wonderous thing they are finding about foam it just plain seals out everything, moisture as well as temp. So it's fine to spray it shut, no worries about moisture causing mold from no air movement, there is none of either. For that reason I would replace the door, spray it closed, and just put in electrical lighting. I agree, not much for mood, but for the lowest cost to get there, it will work.

Also can't tell from the pic, and didn't see anything written. What is the floor? Dirt = BAD. Concrete will help cool in the heat, but totally the opposite in the cold, but hard on your legs, and back. But if it's concrete you can always put foam mats in front of your standing spots. Enough concrete and you can keep the place closed in the Summer, and stay cool enough with a few well placed fans, ceiling are best. In the Winter, you need a heat source, and probably a vented one if you foam it closed.

My concern is all that glass. I'm betting it's all single pane, leaks like a sieve construction. With that glass in the peak it will be like keeping the main door open all the time, heat, and or cooling are gonna roll right out. Worst of that is it's a great source of natural light. What a dogfight.


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## therealSteveN (Oct 29, 2016)

> Open soffit roof on block walls is old school way to build
> 
> - CaptainKlutz


Except for the windows our first place was almost the same building. I put the shop in the basement. For the first bit every penny was going to something other than a shop. I was at ShopSmith then, so the tools I had went downstairs. Soon enough money wasn't as tight, and I ended up going out and renting a shop space. kept that place 29 years. Except for paying the rent that is the way to go.


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## bigJohninvegas (May 25, 2014)

I agree with captainklutz.
Generally estimates are free. I would call a couple roofing contractors and see what they recommend. 
Maybe it's work you can then handle yourself, or maybe you find out you need a pro. 
But if you get it wrong, you will cause all sorts of problems.


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## Finn (May 26, 2010)

The roll up garage door should be insulated using styrofoam sheets. I have done this on two different roll up doors with success.


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## Snipes (Apr 3, 2012)

Those rafters are not equipped to handle much storage as they are. I would spray foam directly to roof myself. There's tons of misleading info on hot roofs, roofers will tell you one thing insulators another. It would be the same as sip, and i have had no issues. Also spraying yourself is not worth it imo, cheaper to hire it done.
Regarding walls, put rigid foam against block, and then use either 2×4 or 1×4 flat to save space.


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## dhazelton (Feb 11, 2012)

Everyone is saying spray foam. I agree but just want you to be sure to use CLOSED CELL spray foam. It's impermeable to moisture and a couple inches of that is an effective air barrier - more than a couple of inches is just a waste of money. You don't need venting because now your roof deck won't have warm moist air coming into contact with it in the winter so rot is not an issue. If you go that route you may want to install a couple of ceiling fans to keep the warm or cool air down low where you want it.


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## nickajeglin (Jul 14, 2019)

Thanks for the good advice everyone. I'm in Nebraska. Spray foam seems to be the consensus, but I am worried that it could hide any leaks from above and hold water there. I totally agree that the rafters need reinforcement. There aren't even any cross beams in the front half, and I can see cracks above the garage door where the roof has been trying to spread the walls.

Considering everything, I like the idea of stripping the roof down to the sheathing and adding a adhered water barrier, and then an insulated roof and new shingles. That would also probably allow me to extend the roofline out past the walls to keep water away from them, and possibly add soffits, internal insulation, and correct ventilation.

That does sound like a project that is too big and expensive for me right now though, so I'm leaning towards something like Carlos drew. That would add some extra support to the rafters, and then I'd also double up the current cross beams for wood storage. When the shingles inetivably need to be replaced, I can add the exterior insulation etc if needed. I will definitely find someone local to come check it out before I start.


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## farmfromkansas (Jun 16, 2019)

Luckily you have a gable roof, so you can put gable vents in there, and some roof vents on roof to achieve the ventilation for the attic, and you need to add ceiling joists like the existing ones, but enough so you have them at least on 24" centers. Nail to the rafters like the existing ones. Then use some R30 batts and staple them to the ceiling joists, and put up some 5/8" sheetrock, because that is what most inspections require. Less than R 30 in Nebraska will be lacking. Block are poor insulators, fir the walls out like you were saying and use R13 or better batts. If you have a local Menards store, they have insulation on sale regularly.


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## nickajeglin (Jul 14, 2019)

Hi everyone.

Looking a little closer, I realized that I actually do have soffits, they are just very narrow. About 3 inches. I think I can get a skinny strip of soffit vent and run a continuous vent all the way along the eaves, then drill a vent hole for each set of rafters in the board that sits on top of the block walls.

Now I am confused about how to handle the area where the sloped drywall will intersect the joists:










Do I notch the drywall around the joists? Do I stop the drywall where the joists and rafters intersect, then patch in small level pieces over to the top of the block walls? Any better ideas than that?


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## farmfromkansas (Jun 16, 2019)

You would be better off with a flat ceiling at the existing ceiling line. But you would not be able to store lumber up there. I fixed up a similar building, having to add ceiling joists, and bracing to the attic, as well as a ceiling ,insulation and wiring.


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## Delete (May 19, 2017)

There are a couple of options. You could go with 2 X 4 blocking between the rafters every 24" starting tight to your block wall header, install the 2 X 4 blocking face down even with the bottom edge of your rafters, so it doesn't interfere to much with your insulation.

Or you could use 16' long 1 X 4 strapping, starting tight to the wall header, screw or nail them to the bottom edge of your rafters again on 24" centers, this will give a little extra space for your insulation. One way or the other you need them to attach your sheathing too, solidly.

Where your sheathing meets the joists cut slots so the sheathing can go tight to the wall header. I would not use drywall sheathing for the roof of a workshop. Its heavy, not very strong, specially around openings, slots etc. unless it is well supported. 1/2" chipboard or OSB is a better selection. You will get a small amount of additional insulating value, its lighter and easier to work. If your looking for light reflection 2 or 3 coats of a good white semi gloss paint will do. If your worried about air movement at the joints, run a bead of caulk along the edges before the paint goes on. It will also add strength to your roof whereas gyprock (drywall) will mostly just add weight.

If your still going with triangulation half way up the rafter. Heres what I did where the joist meets the rafter. If your concerned about strength, we had 4' deep snow loads this past winter, this shops span is 16'.


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## Knockonit (Nov 5, 2017)

sure is a whole lotta over thinking here, insulation is not rocket science, nor is figuring out the wall stuff.

talk to an insulator , probably cost nothing to get some estimates and along with that some advise, whole lotta conjecture and mis direction going on. jmo.


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## Delete (May 19, 2017)

> sure is a whole lotta over thinking here, insulation is not rocket science, nor is figuring out the wall stuff.
> 
> talk to an insulator , probably cost nothing to get some estimates and along with that some advise, whole lotta conjecture and mis direction going on. jmo.
> 
> - Knockonit


Care to elaborate on that. A contractor is easy if you can afford it, the OP obviously wants to learn how to do it himself. He wants to do a safe installation, as inexpensively as possible with the kind of resources he can work with. If the op just wanted a contractor to come in and handle it, he would not have had to ask the question "How do I do it within my means".


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## Knockonit (Nov 5, 2017)

nothing wrong with getting an estimate and discuss install with a professional, usually no string attached, there is a whole lot of information here that is not in his best interests to try. Most companies will provide information and go thru the process and options, but hey, what do i know, only been building for lifetime. And yeah i get the wanna do it yourself, but sometimes it takes a professional to steer you right the first time. options, fella, lots more options than we can ever think of
hope op gets some professional advice before somethign goes amiss.
R j


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## Delete (May 19, 2017)

Having a contractor give you an estimate is not rocket science I think the OP has considered that but has decided it either is not in his budget or is interested in learning to do it himself. I agree some of the advice is questionable at best, but if you are really concerned for the OP why don't you call it out rather than making insinuations that encompass everyones advice, which is not all questionable. It makes it look like no one can do it right except a contractor and that is just self serving.

I can give you an example where I called out similar ludicrous advice by the same poster, you have probably read it. The reward is it makes you look like the bad guy, so why continue, hopefully the OP recognizes it for what it is.


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## nickajeglin (Jul 14, 2019)

Thanks for the good advice both Carlos and knockonit. Carlos is right that I'm committed to learning to do it myself, which is why I asked here. On the other hand, there is always some screwball advice out there. Hopefully I have enough common sense to separate the wheat from the chaff.

I think bringing in another set of eyes is a good idea. If I'm going to learn, I want to do it right. I generally learn best by ignoring good advice and making bad mistakes, but when the price tag is big enough, I'm a little more cautious.

Our realtor put me in touch with a general renovations guy who is a licensed contractor. I'm going to have him do some electrical work, and it sounds like he's happy to take a look at the roof and point me in the right direction.

In any case, the more I have thought about it, the more it seems like putting the ceiling below the existing joists is the way to go. When I add the missing joists back in, it will be difficult to store large items up there anyways, and this will make lots of things easier: ventilation, drywall/osb sheathing, later access to fix the inevitable mistakes, etc.


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## Delete (May 19, 2017)

Good attitude, good luck Nick.


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## Knockonit (Nov 5, 2017)

great to hear, and don't get in too big a hurry making the big decisions. hopefully some insight by renovations gent will help clear up some ideas.
best of luck


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## bigJohninvegas (May 25, 2014)

> I think bringing in another set of eyes is a good idea. If I m going to learn, I want to do it right. I generally learn best by ignoring good advice and making bad mistakes, but when the price tag is big enough, I m a little more cautious.
> 
> In any case, the more I have thought about it, the more it seems like putting the ceiling below the existing joists is the way to go. When I add the missing joists back in, it will be difficult to store large items up there anyways, and this will make lots of things easier: ventilation, drywall/osb sheathing, later access to fix the inevitable mistakes, etc.
> 
> - nickajeglin


Sound like you are on the right track.
I too try to do all I can myself. Both for money saving and the satisfaction that I did it.
But plenty of jobs have been above my knowledge or skill level. Before I have given in and hired a pro, I have consulted with the pros to help me figure it out, make sure I do it right. 
With this sort of advise I have managed to add two 110v, and a 220v circuit to my shop. (I did hire that pro to install the breaker in the panel), and the rest was on me.

I added a mini split A/C to the shop last year. Tried to go pro all the way with it. I really did not feel I wanted to deal with trying to install my own A/C. 
But a couple bids later, both wanted 6K+ to do it. Way outside of my budget. 
That got me looking at DIY mini splits, and I did it myself. For 2K. I did have that same electrician come back for the 220v circuit breaker. I Just don't like getting into the panel myself. 
But I tell this story, because the free estimates from the pro HVAC guys, gave me the information I needed to go out on my own. (location in the shop for the unit, proper size of A/C unit, and electrical needs.) 
I also have plenty of projects that I have done twice because I screwed it up the first time around. lol. 
We all learn the hard way I think.

So a friend did a similar job that you are about to do some years ago. He wanted to save the 12' ceiling height, but in the end to properly insulate he only had 9'. He has that sloped roof, so he picked a spot in the high side of the shop where he built a pocket into the ceiling. He had to work with the width of the roof trusses. I think they were 18" or 20" on center. And he made it about 5' long. Gave himself a pocket to store a few longer boards, and sheet goods. Seems to work for him. 
Good luck


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## nickajeglin (Jul 14, 2019)

Thanks for all the advice everyone! After talking to the refurb guy, I decided to build the ceiling out under the joists and just insulate that. I got the missing joists reinstalled today. We're back at 24" centers, with due consideration of local snow load (I even bumped it up one level) and heel joints fastened as God and the IBC intended. Next up, I'm sealing leaks and laying in R30 faced batts between the joists. We'll see how it feels after that to decide if I also insulate the walls.

P.S. Framing nailers turn out to be awesome.


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## swandog (Jan 1, 2013)

Don't forget to run electric up there for lights BEFORE you insulate/sheetrock.


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## nickajeglin (Jul 14, 2019)

> Don t forget to run electric up there for lights BEFORE you insulate/sheetrock.
> 
> - swandog


Good advice, but too late! 

R30 batts and Sheetrock is laid in and taped. Electrician is coming on Monday, and running conduit over the sheetrock. It's already way more comfortable in there, but I'm also having him put in an outside box for a mini-split ac/heat pump. Right now I'm tearing out shelving in preparation to seal the inside of the block. As I walk around, I can see light through several areas where the mortar pulled away from the blocks due to the roof missing joists.


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## tvrgeek (Nov 19, 2013)

Read your code. Talk to inspectors. 
For a shop, you want to rock over the insulation. Don't forget the full uninterrupted vapor barrier. There is a lot of information on the WEB for how to insulate. Don't expect woodworkers to know your local code or be professional insulation installers. Spray foam is great , if you can afford it. SOP is 1 to 2 inches of foam, then something cheap over it. Attics typically blown FG. Walls typically bats.

Do run overkill power while it is open.


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## Woodmaster1 (Apr 26, 2011)

In my detached garage I put r19 fiberglass insulation in the walls and r30 in the ceiling. I installed a 50,000 btu bigmaxx furnace and use a 10,000 btu window air conditioner. Furnace was $400 and $0 and a case of beer to run the gas line. Window air unit free neighbor moved and didn't need it anymore. I am warm in the winter (70degrees) and cool in the summer. As far as code goes as long as I do it myself and do it right I am not worried about a subpar job that some contractors will give you. I only got an inspection when the garage was built . Just the basic wiring and plumbing was inspected. I installed my own 200amp panel and the inspector gave it flying Colors. Everything I have done after the final inspection was on my own. I figure if there's an issue when the house is sold my ashes aren't going to worry.


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