Help w/ open ceiling & insulation - new build considerations

[dh128905]

Hi all. I’m in the process of planning my 24x32, 10’ wall detached garage build in NE Ohio. I want to keep the roof open (kayak, paddle board, bike storage + car lift). I also want to heat/cool the space.

What is the most effective way to plan the build for this? For both cost and energy efficiency. I know this will be less efficient than a drywall ceiling, but it is staying open for sure!

Currently having the builders install soffit and ridge vents. Would I be able to do an open foam spray to the ceiling since it will be adequately vented? Also do not want to have any covering over the insulation.

Thank you!!

 

[66Caprice]

I would use attic trusses. that way you have an open attic space you can put down a sub floor in and still be able to insulate the lower floor of the garage for heating. also you could put in a barn style door on the gable end for access.

This is an attic truss.

 

[billconner]

I assume table roof? Will you have rafter ties or a ridge beam?

It sounds like you want a cathedral ceiling "hot roof" design, but that makes no sense with ridge and soffit vents.

I guess I should ask if this will be permitted and thus meet code in regards to the "covering" the insulation. Code would no permit "uncovered" XPS, EPS, or faced batt's.

Any drawings to share?

 

[theoldwizard1]

I want to keep the roof open (kayak, paddle board, bike storage + car lift). I also want to heat/cool the space.

Even with no ceiling, typical truss/rafter/joist spacing will NOT allow a lift ! If you really want a lift, you need scissor trusses or wooden I-beam for rafters or beefed up rafters with collar ties.

If you want to store long awkward things, you had better have those typical truss/rafter/joists spaced 24" apart.

Currently having the builders install soffit and ridge vents. Would I be able to do an open foam spray to the ceiling since it will be adequately vented?

Spray foam on the underside of the roof, YES ! Minimum, 2". 4" would be better.

Open cell, NO ! Open cell foam is a sponge. It will hold moisture and rot wood.

 

[Rusty Wrench]

This is my 20 x 30 in Lake Co OH. To get tall ceilings as wide as possible the architect drew a gambrel roof that needed to be stick framed. He said the truss company wasn't set up for those extreme low and high pitches. 2x6 framing allowed for R19 everywhere. There is a low loft area across the back 10 feet. I've been very happy with the building. 15 years now.

 

[theoldwizard1]

Will you have rafter ties or a ridge beam?

A true ridge beam would be good, but more expensive and requires a column at each end. Acceptable for a reverse gable roof.

 

[theoldwizard1]

To get tall ceilings as wide as possible the architect drew a gambrel roof that needed to be stick framed.

Gambrel roofs are great for storage, but they still have a ceiling that will not allow a lift, if that really is a priority.

 

[Firebrick43]

Gambrel roofs are great for storage, but they still have a ceiling that will not allow a lift, if that really is a priority.

What are you talking about?

Gambrel roofs don’t require ceilings. Or ties, which is why they were used in hay mows in millions of barns across the country.


And while I think heating rafter space is an absolutely ridiculous proposition to me, there is no issue having a car lift go up into the rafters. You can use a 2x10 or 2x12 as a top plate on the wall to stiffen them and put cables with turn buckle rafter ties in front of and behind the lift.

 

[wssix99]

If you have vents in the roof, what's the point in insulating it??? (The heat is going to go right out of the top.)

Are you going to heat or condition the space? (If so, you don't vent the space you are conditioning.)

 

[Rusty Wrench]

Gambrel roofs are great for storage, but they still have a ceiling that will not allow a lift, if that really is a priority.

I have a 4 post lift in there. The high ceiling w low pitch allows for maximum lift.

 

[theoldwizard1]

I have a 4 post lift in there. The high ceiling w low pitch allows for maximum lift.

Interesting !

Your plans show 11' clearance to a 10" ceiling joist ! Unless the lift is short, many vehicles would hit that.

It also show a 10" collar tie at the gambrel joint, so maybe that 11' clearance is only under the loft.

 

[billconner]

It seems if

Currently having the builders install soffit and ridge vents.

it may be beyond gambrel versus gable. But for that matter, a hip roof is not suppose to require rafter ties, so you could look at that.

Code does not allow uncovered foam, though intumescent coatings ($$$) can solve that. (Do you really want to see uncovered foam?)

If its designed and under construction with table roof, soffit and ridge vents, and you want a vented roof, and can live with some rafter ties (and maybe a wide top plate to bridge between rafter ties on 4 or 6 foot centers), a continuous vent baffle can work. Probably simplest to just sheath bottom of rafters with foil faced poly iso - as thick as you can afford - 2 staggered layers ideally - seams foil taped. Insulation, code compliant, vented roof, storage on collar ties (probably 2x10s or 12s).

Knowing what's not changeable or modifiable at this point would lessen the guessing.

 

[billconner]

Interesting !

Your plans show 11' clearance to a 10" ceiling joist ! Unless the lift is short, many vehicles would hit that.

It also show a 10" collar tie at the gambrel joint, so maybe that 11' clearance is only under the loft.

I believe that joist at 11' is only in loft area, not open area in front of it. More like 14' clear in front of loft.

 

[dh128905]

Even with no ceiling, typical truss/rafter/joist spacing will NOT allow a lift ! If you really want a lift, you need scissor trusses or wooden I-beam for rafters or beefed up rafters with collar ties.

If you want to store long awkward things, you had better have those typical truss/rafter/joists spaced 24" apart.

Spray foam on the underside of the roof, YES ! Minimum, 2". 4" would be better.

Open cell, NO ! Open cell foam is a sponge. It will hold moisture and rot wood.

The 2 post lift I’m getting is the Benpak GranPrix GP-7LC. It is 118.5” with a lifting height of 68”. It is designed for 10’ ceilings. It’s just for my track cars that are all 50” tall or less. I can’t go higher ceilings due to building code.

I assume table roof? Will you have rafter ties or a ridge beam?

It sounds like you want a cathedral ceiling "hot roof" design, but that makes no sense with ridge and soffit vents.

I guess I should ask if this will be permitted and thus meet code in regards to the "covering" the insulation. Code would no permit "uncovered" XPS, EPS, or faced batt's.

Any drawings to share?

The drawings have not been done yet. Rafters are 2x6 16” oc. Horizontal Rafter ties are are 2x8 48” oc. Below are a couple of still frame from one of the builder’s videos. It’s a garage company that builds 300 garages a year, so they’re all the basically the same.

If you have vents in the roof, what's the point in insulating it??? (The heat is going to go right out of the top.)

Are you going to heat or condition the space? (If so, you don't vent the space you are conditioning.)

I will have rafter baffles that connect the the soffit and ridge vents so there is a continuous passage of air. Insulation over rafter baffles. Will still be a cold roof

It seems if

it may be beyond gambrel versus gable. But for that matter, a hip roof is not suppose to require rafter ties, so you could look at that.

Code does not allow uncovered foam, though intumescent coatings ($$$) can solve that. (Do you really want to see uncovered foam?)

If its designed and under construction with table roof, soffit and ridge vents, and you want a vented roof, and can live with some rafter ties (and maybe a wide top plate to bridge between rafter ties on 4 or 6 foot centers), a continuous vent baffle can work. Probably simplest to just sheath bottom of rafters with foil faced poly iso - as thick as you can afford - 2 staggered layers ideally - seams foil taped. Insulation, code compliant, vented roof, storage on collar ties (probably 2x10s or 12s).

Knowing what's not changeable or modifiable at this point would lessen the guessing.

Yes I don’t care what it looks like! All about function

 

[theoldwizard1]

The drawings have not been done yet. Rafters are 2x6 16” oc. Horizontal Rafter ties are are 2x8 48” oc.

It really depends on where the horizontal members are located. Rafters ties are typically located 2/3 of the distance below the ridge. Collar ties are 1/3 the distance below the ridge.

Glad to hear you hired an architect !

 

[dh128905]

It seems if

it may be beyond gambrel versus gable. But for that matter, a hip roof is not suppose to require rafter ties, so you could look at that.

Code does not allow uncovered foam, though intumescent coatings ($$$) can solve that. (Do you really want to see uncovered foam?)

If its designed and under construction with table roof, soffit and ridge vents, and you want a vented roof, and can live with some rafter ties (and maybe a wide top plate to bridge between rafter ties on 4 or 6 foot centers), a continuous vent baffle can work. Probably simplest to just sheath bottom of rafters with foil faced poly iso - as thick as you can afford - 2 staggered layers ideally - seams foil taped. Insulation, code compliant, vented roof, storage on collar ties (probably 2x10s or 12s).

Knowing what's not changeable or modifiable at this point would lessen the guessing.

This is what I need! I have not signed yet, wanting to figure all this out first. So I can change anything, but …. This is a garage company that builds very similar garages. 300 a year. That has its drawbacks, but they are 20% cheaper than anyone else. My brother in law has used them twice for basic garage builds and they are perfectly fine. All Amish crews out here in Ohio

But… do I say forget the venting and just pay the money for closed cell spray insulation and be done with it? This garage will have ac or heat on probably 40-50 days a year at most. But I want it done right from the beginning

 

[dh128905]

It really depends on where the horizontal members are located. Rafters ties are typically located 2/3 of the distance below the ridge. Collar ties are 1/3 the distance below the ridge.

Glad to hear you hired an architect !

I don’t know why I said drawings. No drawings, this is a basic garage by a company that builds very close to the same garage everywhere… which I am fine with.

He did say there will be collar ties. I will ask him more details regarding that. What do you mean when you say horizontal members? Aren’t those just the 2x8 rafter ties that are 48” OC. This is my first time having anything built, so I am learning.

 

[Firebrick43]

This is what I need! I have not signed yet, wanting to figure all this out first. So I can change anything, but …. This is a garage company that builds very similar garages. 300 a year. That has its drawbacks, but they are 20% cheaper than anyone else. My brother in law has used them twice for basic garage builds and they are perfectly fine. All Amish crews out here in Ohio

But… do I say forget the venting and just pay the money for closed cell spray insulation and be done with it? This garage will have ac or heat on probably 40-50 days a year at most. But I want it done right from the beginning

Have you considered using a tradition ceiling but framing a well where the lift sets?

 

[dh128905]

Have you considered using a tradition ceiling but framing a well where the lift sets?

I have seen people modify the build to accommodate a lift. I have been meaning to ask the builder about that. As mentioned above, this is a garage company that builds largely the same garages, so I don’t think they’d do that without a huge increase in price. Start to finish it is a 2 day process. 20% less than any other quote I got. And yes my bro in law who is an engineer has had them build 2 garages for him, so I trust him

 

[Firebrick43]

I have seen people modify the build to accommodate a lift. I have been meaning to ask the builder about that. As mentioned above, this is a garage company that builds largely the same garages, so I don’t think they’d do that without a huge increase in price. Start to finish it is a 2 day process. 20% less than any other quote I got. And yes my bro in law who is an engineer has had them build 2 garages for him, so I trust him

I get the framing crew/pricing thing but they can lay regular ceiling joist skipping where the lift will be and you can frame that one section.

Or did I read it wrong and you are not DIY anything?

 

[dh128905]

I get the framing crew/pricing thing but they can lay regular ceiling joist skipping where the lift will be and you can frame that one section.

Or did I read it wrong and you are not DIY anything?

I’m not really sure.. can you post a pic of what you mean? And I will have rafter ties, not ceiling joists. They are 4x8s, 48” oc. I need to clarify how much bracing and home many perpendicular strong holds there will be. But anyway… I think I should have a ton of room to have a 2 post lift extend up into the ceiling. Or is there something I’m not seeing? Which is certainly possible..

I figured where I want to add ceiling storage, I could add some additional vertical braces between rafter and rafter ties.

 

[theoldwizard1]

He did say there will be collar ties. I will ask him more details regarding that. What do you mean when you say horizontal members? Aren’t those just the 2x8 rafter ties that are 48” OC. This is my first time having anything built, so I am learning.

"Horizontal members" is a generic term for either collar ties or rafters ties.

 

[Firebrick43]

I’m not really sure.. can you post a pic of what you mean? And I will have rafter ties, not ceiling joists. They are 4x8s, 48” oc. I need to clarify how much bracing and home many perpendicular strong holds there will be. But anyway… I think I should have a ton of room to have a 2 post lift extend up into the ceiling. Or is there something I’m not seeing? Which is certainly possible..

I figured where I want to add ceiling storage, I could add some additional vertical braces between rafter and rafter ties.

There is an old saying that

You can have it cheap

You can have it fast

You can have high quality

But you have to pick two, you can have all three

Your trying to pick all three.

A conventional ceiling is the most common as it give the best energy performance per dollar spent. Probably even cheaper than a sprayfoamed rafters without the negatives.

But your probably going to have to do that work yourself as you appear to be on a tight budget.

Storing things in the rafters/rafter ties is not a wise idea you can store things on top of joist depending on how you size them.

There are lots of choices, you have to pick which features are the most important

 

[dh128905]

There is an old saying that

You can have it cheap

You can have it fast

You can have high quality

But you have to pick two, you can have all three

Your trying to pick all three.

A conventional ceiling is the most common as it give the best energy performance per dollar spent.

I don’t think there is anything wrong with quality of the build. I just want open ceilings since I am restricted to 10’ walls. I am going to ask them about modifying the area where the lift is, but I don’t see a lot or value in that given that my track cars are less than 50” tall. If it’s only a couple grand then sure, why not

"Horizontal members" is a generic term for either collar ties or rafters ties.

Ok so 2x6 rafters are 16” OC, 2x8 rafter ties are 48” oc along with the collar ties above it. Then there are diagonal supports tied in as well. Your basic, no attic type build

 

[Youngandfree]

I don’t think there is anything wrong with quality of the build. I just want open ceilings since I am restricted to 10’ walls. I am going to ask them about modifying the area where the lift is, but I don’t see a lot or value in that given that my track cars are less than 50” tall. If it’s only a couple grand then sure, why not

Ok so 2x6 rafters are 16” OC, 2x8 rafter ties are 48” oc along with the collar ties above it. Then there are diagonal supports tied in as well. Your basic, no attic type build

Just have them build it the way they are going to using open rafters like you said and spray foam the roof just like you said in the original post. All of these suggestions are mostly irrelevant.

 

[theoldwizard1]

Ok so 2x6 rafters are 16” OC, 2x8 rafter ties are 48” oc along with the collar ties above it.

Rafter ties AND collar ties ? Usually one or the other. Seems odd. What is the size and spacing of the collar ties ?

Then there are diagonal supports tied in as well. Your basic, no attic type build

I don't understand what "diagonal supports" are in a roof.

 

[billconner]

Don't forget raising the rafter ties reduces the span of the rafter - so may have to up size rafter. Simple calculation spelled out in building code.

Rafter ties AND collar ties ? Usually one or the other.

They do address entirely different issues - rafter thrust from snow losd versus up-lift from wind. I don't see collar ties often but never lived in hurricane/tornado areas.

 

[dh128905]

Don't forget raising the rafter ties reduces the span of the rafter - so may have to up size rafter. Simple calculation spelled out in building code.


They do address entirely different issues - rafter thrust from snow losd versus up-lift from wind. I don't see collar ties often but never lived in hurricane/tornado areas.

Right. Talking about doing 2x12 rafters, which will allow space for r30 batt insulation, and hopefully add enough strength to raise the rafter ties. He also mentioned that they would “stick scissor frame at no extra cost.” I have questions out for clarification. Definitely don’t want to weaken the structure.

Rafter ties AND collar ties ? Usually one or the other. Seems odd. What is the size and spacing of the collar ties ?



I don't understand what "diagonal supports" are in a roof.

Yeah, both. My understanding is they do different functions too.

By diagonal supports, I meant vertical supports from framers down to rafter ties that run at a diagonal.

 

[theoldwizard1]

He also mentioned that they would “stick scissor frame at no extra cost.”

Scissor frame (truss) will NOT have a flat surface to store long items on


You should check the cost between wooden I-beams and 2x12.

Or add 2x6 purlins, standing up, before applying the decking.

By diagonal supports, I meant vertical supports from framers down to rafter ties that run at a diagonal.

Sorry, I still do not understand.

 

[njk4o5]

mine is 30x40. i did 2x10 rafters and rafter ties 1/3" the way up. 18" concrete and 8' studs all around gave me a 12' ceiling

 

[dh128905]

@billconner @theoldwizard1 @Youngandfree Thank you, I am much better educated on this now. I am going to do scissor truss’ for cathedral type ceiling, and closed cell foam insulation on underside of roof. Maybe for the walls too since those are 2x4s. With that being said, I can tell the builders not to install any type of roof vents. Is this correct? Don’t want to make a costly mistake!

Even though the spray foam is expensive, I think it’s the best option. If I wanted to use batt insulation, the builder said he would use 2x12 rafters for an additional $2k. I didn’t ask about an upgrade to 2x6 studs, but guessing that would also be another $2k. And then money and time for me to install all the insulation….

 

[Youngandfree]

@billconner @theoldwizard1 @Youngandfree Thank you, I am much better educated on this now. I am going to do scissor truss’ for cathedral type ceiling, and closed cell foam insulation on underside of roof. Maybe for the walls too since those are 2x4s. With that being said, I can tell the builders not to install any type of roof vents. Is this correct? Don’t want to make a costly mistake!

Even though the spray foam is expensive, I think it’s the best option. If I wanted to use batt insulation, the builder said he would use 2x12 rafters for an additional $2k. I didn’t ask about an upgrade to 2x6 studs, but guessing that would also be another $2k. And then money and time for me to install all the insulation….

2x6 walls can have 24" stud spacing. Makes the cost difference close enough to zero to make it worth the upgrade.

 

[dh128905]

2x6 walls can have 24" stud spacing. Makes the cost difference close enough to zero to make it worth the upgrade.

Thanks for the suggestion, but I’m not giving up 4” of space in my already tight 24’ wide garage! Id also rather have 16” oc for hanging things and getting the osb panels into 4 studs

I’m still debating just closed cell foam everything and be done with it. I’d probably be between 5 and 6k for ceilings and walls

 

[billconner]

Just noting if following building code, IRC requires 23/32" wood panel (or 1/2" drywall or another approved covering) over foam.

Not mentioned much and not often done, but code does allow 2x4 up tho 19' on 24" centers for one story buildings. With 23/32" panels, wouldn't bother me.