Drywall thickness on walls and ceiling?

Happy Holidays,

A friend of mine bragged about you all, so I had to check it out for myself.
I have a brick (veneer) ranch house with an addition by the previous owner. The previous owner added an attached garage with 2 bedrooms above it. The original brick veneer wall is still intact between the addition and the ranch.

The walls and the ceiling used to be covered with 1/2 inch drywall. I had to remove most of it as they were damaged. I am in the process of converting the garage to a living space. I have replaced the garage door with a picture window already. I have also added new duct work on the ceiling to supply the new living space as well as the bedrooms upstairs. I am planning on using dropped ceiling to cover all the new duct work, plumbing and the wires.

Could any of you please help me with the following questions?

1. Since this place no longer will be used as a garage, what thickness of drywall do I need to use on the walls? The walls are made out of: outside brick veneer, Tyvek, 1/2 inch OSB sheeting, 2X4 wood studs 16" OC, fiberglass insulation.

2. You can see the floor joists (2x8 wood 16" OC) and the fiberglass insulation in the ceiling. What thickness of drywall do I need to use on the ceiling?

3. The new ductwork as well as some of the plumbing was laid in between the floor joists and hangs lower than the floor joists. Does the drywall have to cover all the ductwork, plumbing and the wires?

4. Does the dropped ceiling change anything?

I have tried to find the answers in the International Building Code, but was confused even more. I don't believe the previous drywall selections were correct, but now that it is no longer a garage, I can't find if I need to use 1/2" or 5/8" drywall.

I am sorry for the long post and numerous questions. I would like to thank you all in advance for your guidance...

Happy New Year!

P.S. I have pulled permits for each job from the city.

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1. Since this place no longer will be used as a garage, what thickness of drywall do I need to use on the walls? The walls are made out of: outside brick veneer, Tyvek, 1/2 inch OSB sheeting, 2X4 wood studs 16" OC, fiberglass insulation.

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SB: 1/2" drywall.

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2. You can see the floor joists (2x8 wood 16" OC) and the fiberglass insulation in the ceiling. What thickness of drywall do I need to use on the ceiling?

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SB: 1/2" drywall.

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3. The new ductwork as well as some of the plumbing was laid in between the floor joists and hangs lower than the floor joists. Does the drywall have to cover all the ductwork, plumbing and the wires?

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SB: Yes.

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4. Does the dropped ceiling change anything?

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SB: Yes, it does.

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I have tried to find the answers in the International Building Code, but was confused even more.

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SB: Not to worry, that happens to the best of us.

Thanks for all the answers. Could you please explain what does the dropped ceiling change?

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4. Does the dropped ceiling change anything?
SB: Yes, it does.

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Originally Posted by Sako Beg

4. Does the dropped ceiling change anything?

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Explain the dropped ceiling better.

Are you referring to dropping the entire ceiling down or just soffit areas?

The required fireblocking in the walls is to be at the ceiling level.

Am unclear as to what systems you may have in this former garage space. It seems you intend to incorporate it into the conditioned envelope of the living space. I assume your intent is to convert the now conditioned space to all or mostly habital space as well, is this correct?

You would likely need to remove (possibly replace) the insulation in the ceiling cavity of the former garage and remove the above floor side kraft paper or other moisture inhibitor, which would be on the former warm side (bedroom floor) of the separation.

Generally floor ceiling assemblies have 5/8" gyp on the underside to protect the joists for a time certain so as to allow the occupants of the bedrooms above a certain evac time should there be a fire in the former garage. Utility areas in the former garage space may also require 5/8 on the walls to separate them from the newly created habital space, depending on what appliances are installed and their proximity to the walls.

1/2" on the other walls is usually sufficient.

Personally I would remove any former exterior exposure/separation wall sheathing and finishing (i.e. tyvek, tar paper, brick veneer, replacing SHEER required OSB or plywood where needed for stability) so as to prevent a moisture/conditioning problem down the road.

Generally garage floor slabs and footers aren't usually moisture/radon sealed nor have a thermal break. Usually they are lower than the threshold and floor level of the habital space, are often sloped and/or have floor or gutter drains. Often the exterior topography promotes flow towards and away the former driveway apron to the drive.

You might wish to consult the IRC rather than the IBC regarding your former ranch style residence, with 2-story bedroom over attached garage addition, now converting former garage space.

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Generally floor ceiling assemblies have 5/8" gyp on the underside to protect the joists for a time certain so as to allow the occupants of the bedrooms above a certain evac time should there be a fire in the former garage. Utility areas in the former garage space may also require 5/8 on the walls to separate them from the newly created habital space, depending on what appliances are installed and their proximity to the walls.

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HG: Please provide IRC citations to support your claim that 5/8" drywall is required either on the walls or the ceiling of anything other than a garage.

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Originally Posted by A.D. Miller

HG: Please provide IRC citations to support your claim that 5/8" drywall is required either on the walls or the ceiling of anything other than a garage.

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I made no such claim.

I did not use the word required nor did I state or imply any citation to the unammended IRC of any particular edition.

Generally, Listed floor ceiling assemblies using 2x8" sawn wood joists (current requirements often minimum 2x10s or equivallent). Regarding the separation requirements for utility rooms - depends on the appliances and their proximity to walls regarding their listing installation instructions/requirements. 2-story +attic usually now better than 2x4 bearing walls.

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I made no such claim.

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HG: True, but you may have implied it to be a common practice. Not so in my area.

(bold and underlining are mine)

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Originally Posted by H.G. Watson, Sr.

Utility areas in the former garage space may also require 5/8 on the walls to separate them from the newly created habital space, depending on what appliances are installed and their proximity to the walls.

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Originally Posted by Jerry Peck

(bold and underlining are mine)

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JP: He said "may", but this is December. Does that make a difference?:confused:

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Originally Posted by A.D. Miller

JP: He said "may", but this is December. Does that make a difference?:confused:

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Actually, he said "may also REQUIRE" ... followed by "depending on", which means there is a set of conditions which "REQUIRE" the 5/8" on the ceiling, and ... either there is a "requirement" or there is not, it cannot be both ways.

H.G. did say "require" and specified that it would be "depending on" what was further stated.

H.G. later posted:

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I made no such claim.

I did not use the word required nor did I state or imply any citation to the unammended IRC of any particular edition.

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Technically, H.G. did not use THE WORD "required", but he did state that it "may REQUIRE"..."depending on" the stated options.

As Sako lives in Indy, he/she and has permitted the addition and conversion work on this home. I would assume that the AHJ would be the one for him/her to contact to findout exactly what they will require.

To avoid confusion, IRC being the Indiana Residential Code.

There's a lot of changes, I'll just highlight a quick few right off the start:

Rule 4.3 Indiana Residential Code
675 IAC 14-4.3-1 Adoption by reference.
Sec. 1 (a) those certain documents being titled the 2003 International Residential Code for One and Two Family Dwellings fifth printing, and Chapter 43 of the 2006 International Code for One and Two Family Dwellings, first printing, published by the International Code Council, 5203 Leesburg Pipe, Suite 708, Falls Church, Virginia 22041-3401, are hereby adopte by reference as if fully set out in this rule save and except those revisions made in this rule.
(b) This rule shall be:
(1) known as the Indiana Residential Code, 2005 edition; and
(2) published, except incorporated documents, by the department of homeland security for general distribution and use under that title.

675 IAC 14-4.3-2 Chapter 1; administration
Sec. 2. Delete Chapter 1 and substitute the following:

.....

(c) SECTION R104 is added to read as follows: SECTION R104 EXISTING CONSTRUCTION For existing construction, see the General Administrative Rules (675 IAC 12-4) and local ordinance
(e) SECTION R105 is added to read as follows: SECTION R105 ADDITIONS AND ALTERATIONS Aditions and alterations to any structure shall conform to that required fgor a new structure without requiring the existing structure to comply with all the requirements of this code. Additions or alterations shall not cause an existing structure to become unsafe.
(f) SECTION R106 is added to read as follows: SECTION R106 ALTERNATE MATERIALS, METHODS AND EQUIPMENT
SECTION R106.1 ALTERNATE MATERIALS, METHODS, AND EQUIPMENT
The provisions of this code are not intended to limit the appropriate use of materials, appliances, equipment, or methods of design or construction not specifically prescribed by this code. The building official shall determine equivalence of the proposed alternate materials, appliances, equipment, or method of design or construction of that prescribed in this code in suitability, quality, strength, effectiveness, fire resistance, durability, dimensional stability, safety, and sanitation on the basis of evidence and/or tests as described in R106.2 and R106.3, as suitable to be approved. For Class I structures, alternate materials, methods, equpment, and design shall be as required by the General Administrative Rules (675 IAC 12-6-11). Compliance with specific provisions of the Indiana Bujilding Code (675 IAC 14) or the Indiana Plumbing Code (675 IAC 16) in lieu of the requirements of this code shall be permitted as an alternate.
...

675 IAC 14-4.3-3 Section R202; definitions
Sec. 3 Change Section R202 definitons as follows:
(10) change the definition of FIREBLOCKING to read as follows: Building materials, or materials labeled for use as fireblocking, installed to resist the free passage of flame to other areas of the building through concealed spaces.
(14) Add the following definitions after INSULATING SHEATHING:
INTERNATIONAL BULDING CODE means the Indiana Building Code (675 IAC 13)
ICC ELECTRICAL CODE means the Indiana Electrical Code (675 IAC 17)
INTERNATIONAL FIRE CODE means the Indiana Fire Code (675 IAC 22)
INTERNATIONAL FUEL GAS CODE means the Indiana Fuel Gas Code (675 IAC 25)
INTERNATIONAL MECHANICAL CODE means the Indiana Mechanical Code (675 IAC 18)
INTERNATIONAL PLUMBIING CODE means the Indiana Plumbing Code (675 IAC 16)

(15) Delete the definition of LABELED and substitute to read as follows: LABELED. Equipment or materials to which has been attached a label, symbol, or other identifying mark of an organization engaged in product evaluation that maintains perioic inspection or production of labeled euqipment or materials and by whose labeling the manufacturer indicates compliance with appropriate standards or performance in a specified manner.
(18) Add a definition of NATIONAL ELECTRICAL CODE after MULTIPLE STATION SMOKE ALARM to read as follows: NATIONAL ELECTRICAL CODE means the Indiana Electrical Code (675 IAC 17)
(28) Add a definition of SLAB-ON-GRADE FLOOR INSULATION aftrer SYLIGHT AND SLOPED GLAZING to read as follows: SLAB-ON-GRADE-FLOOR INSULATION means insulation around the perimeter of the floor slab or its supporting foundation.
(29) Add a definition of SOLE PLATE after the definition of SOLAR HEAT GAIN COEFFICIENT (SHGC) to read as follows: SOLE PLATE means in frame construction the horizontal member of a frame wall or partition that rests on any type floor.
(34) Add a definition of WORKMANSHIP after the definition of WOOD STRUCTURAL PANEL, to read as follows: WORKMANSHIP means the installation, application, or construction of materials, equipment, or fixtures as they are intended to be incorporated into a one-or-two-family dwelling as mandated by this code, the manufacturer, or industry standards. Items that are aesthetic in nature and that do not affect the livability, intended use, or the safety of a structure are excluded.

note: The former exterior brick veneer wall now interior wall would have an airspace between the brick and the sheathing.

note: We do not know if there is a utility room or appliances in the soon to be former garage space. We further do not know if there are fuel fired appliances in the space, the clearances and separations for the appliance space, etc.

the Indiana Residential Code and the other Indiana Codes speak to the subject.

I agree with SP that the local office would be the best resource, especially since detailed plans should have been submitted with the permit application(s), as per Indiana Admistrative Rule.

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Originally Posted by Sako Beg

Happy Holidays,


The walls and the ceiling used to be covered with 1/2 inch drywall. I had to remove most of it as they were damaged. I am in the process of converting the garage to a living space. I have replaced the garage door with a picture window already. I have also added new duct work on the ceiling to supply the new living space as well as the bedrooms upstairs. I am planning on using dropped ceiling to cover all the new duct work, plumbing and the wires.

Could any of you please help me with the following questions?

1. Since this place no longer will be used as a garage, what thickness of drywall do I need to use on the walls? The walls are made out of: outside brick veneer, Tyvek, 1/2 inch OSB sheeting, 2X4 wood studs 16" OC, fiberglass insulation.

2. You can see the floor joists (2x8 wood 16" OC) and the fiberglass insulation in the ceiling. What thickness of drywall do I need to use on the ceiling?

3. The new ductwork as well as some of the plumbing was laid in between the floor joists and hangs lower than the floor joists. Does the drywall have to cover all the ductwork, plumbing and the wires?

4. Does the dropped ceiling change anything?

I have tried to find the answers in the International Building Code, but was confused even more. I don't believe the previous drywall selections were correct, but now that it is no longer a garage, I can't find if I need to use 1/2" or 5/8" drywall.

I am sorry for the long post and numerous questions. I would like to thank you all in advance for your guidance...

Happy New Year!

P.S. I have pulled permits for each job from the city.

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Separation wall and ceiling used to be covered with 1/2" drywall he stated. Removed due to damage (of unknown type).
Leaving exposed insulation and ceiling/floor joists.

Referring to International Building Code unammended. Needs to refer to Indiana Residential Code. Date of original addition unknown. 1/2" gyp doesn't "jive" with history of adoptions for IN in quite some time for separation of attached garage and habital space. Yet property was described as a ranch yet 2-story addition (bedrooms over garage)?
Indiana has completely re-written Chapter 11 (have to insulate the slab floor and/or footings perimeter, etc.) and also most every reference to fireblocking required and materials used for same. Significant changes to R301.2.2.2.1, completely re-written Table R301.5, and other sections.

Already likely overspanned under supported 2x8s which sleeping rooms require Indiana Res Code 30 live plus dead load now adding more dead load.

HG: Was that intended as a filibuster or simply a magnus opus? It may have failed in the case of the latter.:D

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Originally Posted by Jerry Peck

Explain the dropped ceiling better.

Are you referring to dropping the entire ceiling down or just soffit areas?

The required fireblocking in the walls is to be at the ceiling level.

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I am planning on using Armstrong suspended 2X2 ceiling tiles to cover the whole ceiling about 16" from the actual ceiling drywall.

Thanks to all who have taken the time to respond. Yes, I will try to find the IBC and will try to consult the building inspector. I used 5/8 drywall in the utility room that will have an electric water heater as well as an electric heat pump furnace. The floor joists are supported by iron beams/columns as well. The addition is about 25 years old and was done with a permit (and hopefully was inspected) at the time.
Meanwhile, I appreciated all the answers and guidance you all have provided.

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Originally Posted by Sako Beg

I will try to find the IBC and will try to consult the building inspector.

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Look for the IRC (in your case that would mean the Indiana Residential Code instead of the International Residential Code) as the IRC applies to one- and two-family dwellings and townhouses, and you have, by your description, a one-family dwelling (a ranch style house) and would be under the residential code (IRC).

Just curious, after you install drywall on the underside of the joists above, why are you then planning on dropping the ceiling down?

The Code is the minimum, NOT the maximum.
- put at least one layer 5/8" everywhere; much better wall, cost difference is minimal; you won't have to speculate whether it's ok or not.
- If this job has a permit, why are you even here, why aren't you talking to the muni inspector, doesn't make sense.
- Why go with a cheesy dropped acoustical ceiling? Ductwork inside? Are you going to insulate the ceiling or assume the dropped ceiling, upper drywall and old insulation are enough? How about insulation at the perimeter walls and where the old overhead door was?
- What about your floor over the concrete? Vapor barrier, treated 2x, etc.
- Garages typically have rodent holes. Are you addressing those?
- Does the OVH door area and sides slope away from the walls? Did you get seepage under the OVH door before. If you did, you'll get seepage under the wall if you don't correct the slope.
A sheet of drywall is +/- $7 and whether to go 1/2 or 5/8 is your big concern? I've converted and inspected many such garage conversions. The conversions that don't seem to be a comfortable space to be in or have problems are usually because people didn't address the right issues.

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Originally Posted by Markus Keller

The Code is the minimum, NOT the maximum.
- put at least one layer 5/8" everywhere; much better wall, cost difference is minimal; you won't have to speculate whether it's ok or not.
- If this job has a permit, why are you even here, why aren't you talking to the muni inspector, doesn't make sense.
- Why go with a cheesy dropped acoustical ceiling? Ductwork inside? Are you going to insulate the ceiling or assume the dropped ceiling, upper drywall and old insulation are enough? How about insulation at the perimeter walls and where the old overhead door was?
- What about your floor over the concrete? Vapor barrier, treated 2x, etc.
- Garages typically have rodent holes. Are you addressing those?
- Does the OVH door area and sides slope away from the walls? Did you get seepage under the OVH door before. If you did, you'll get seepage under the wall if you don't correct the slope.
A sheet of drywall is +/- $7 and whether to go 1/2 or 5/8 is your big concern? I've converted and inspected many such garage conversions. The conversions that don't seem to be a comfortable space to be in or have problems are usually because people didn't address the right issues.

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MK: Good points.

Since the previous drywall was 1/2", I did not consider that I might need a different size. I placed some 1/2" on the walls already and I have already bought and picked up the 1/2" drywall. The cost was not a major concern. The ease of placement was a big advantage for me.
I wanted to use suspended ceiling to hide the plumbing and heating/cooling ducts. It seemed like a good solution at the time. Before I found out about the regulations, I was not even thinking about replacing the missing drywall from the ceiling since I was planning on using the suspended ceiling. There is insulation in between the floor joists.
I had addressed all the other concerns about converting a garage to a living space. Thanks to all who brought them to my attention.
I do have an appointment with the building inspector on wednesday. I just wanted to be prepared and since I was overwhelmed with the IBC (2009 edition), a friend of mine recommended that I post in this forum. He was right - you all have been very helpful.
My biggest mistake was to assume that the drywall that was there before was the right size. I should have asked those questions before :-)
Once again, I am grateful for all your help.

After all that he allready used 1/2 inch drywall. :rolleyes:

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Originally Posted by Damon McCarty

After all that he allready used 1/2 inch drywall. :rolleyes:

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Just to clarify, I had already used a few sheets of 1/2 drywall before I posted.

Oh, Ok, :o

Fellow inspectors - I did an inspection today to locate possible missing insulation in a home that was built in 2006. The infrared camera showed several areas. There was insufficient temperature difference to get a good picture, so I drilled 5 plugs and removed one can light and found insulation in ceiling and exterior walls except the shear wall.
Question - what is the typical placement of insulation at shear wall location?:confused:

You need to be a bit more specific with your question and maybe I need to understand a bit more of your terminology. A shear wall to my understanding could be any wall with sheathing or other devices designed to resist shearing or racking forces.
Than said, insulation could be inside the cavity, outside the wall as sheathing or interior to the wall plane, under certain circumstances. Around here, 99% of all walls in the exterior envelope have cavity insulation regardless of whether any additional insulation is applied outside of that cavity.

A picture would help.