Attic Space Options

[VirginiaCodeQuestion]

Hi everyone,

I have an attic space with the dimensions shown in the image. I've been doing research on how I can make this an insulated and usable space. I'm coming across a lot of terminology (Occupiable, Habitable, Living, Accessory Storage Space). I'm not concerned about what it needs to be called, as long as it is safe. I have space downstairs to add code-compliant stairs, windows and other safety measures, but the space is slightly too small to meet the rule of 7's (50% of the ceiling would not be at 7'). Can I legally do anything with this space?

Any guidance or suggestions would be great!


Note: There is a load bearing wall in the middle of the span (about 11').

 

[classicT]

• Ceiling joists look ok for span depending on species; HF#2 can span 13'2" @30psf-LL/10psf-DL (Table R502.3.1(1)).
• Depending on your required insulation R-value, the rafters may not be deep enough; can fur down, but this cuts into ceiling height which is already an issue.
• Need to carefully think about where the stair opening will be framed; will need to likely add some beams or at least double/sister some joists.
• Think about any purlins, venting (DWV or mechanical), etc. that currently is run through the attic.

Overall, looks like you just need to sit down and draft up the plans. I would say that insulation on the ceiling and ceiling height are likely to be the biggest challenges ahead of you.

Regarding ceiling height, you will need to comply with Section R305 if the space is to be anything other than accessory attic storage. Any habitable use will require that you provide the required floor area of the room with a ceiling height of not less than 5 feet and not less than 50 percent of the required floor area shall have a ceiling height of not less than 7 feet (R305.1 Exception #1). I'm just not sure that you will be able to do that, particularly if you have to fur the ceiling down for insulation.

[RB] HABITABLE SPACE. A space in a building for living, sleeping, eating or cooking. Bathrooms, toilet rooms, closets, halls, storage or utility spaces and similar areas are not considered habitable spaces.

 

[north star]

@ ~ @

** classicT **, ...I wonder if the existing 2 x 8 ceiling joists could be raised
and re-attached somehow.

@ ~ @

 

[classicT]

@ ~ @

** classicT **, ...I wonder if the existing 2 x 8 ceiling joists could be raised
and re-attached somehow.

@ ~ @

Raising the ceiling joists would decrease the head room. Do you mean raise the rafters?

If so, then the issue becomes one of using the ceiling joists as the rafter tie to resist the outward spread of the roof framing. See IRC Fig R802..4.5.

 

[Paul Sweet]

You would probably have to build a dormer to get the required 7 ft. ceiling over 35 sq. ft. The dormer ridge would have to be above the main roof ridge to have space for the ridiculous insulation requirements.

Years ago we raised a 5 to 12 sloped roof to 10 to 12 to create an attic bedroom. We had to scab longer rafters to the existing ones. I think we had to use metal straps to tie the raised rafters to the floor joists.

 

[north star]

@ ! @

** classicT **, ...thanks for your quick reply !

I cannot visualize how raising the ceiling joists will decrease
the headroom height ( 7 ft. )..........I would think that raising them
and then re-attaching them to the rafters would meet the 7 ft.
height requirement.

@ ! @

 

[classicT]

You would probably have to build a dormer to get the required 7 ft. ceiling over 35 sq. ft. The dormer ridge would have to be above the main roof ridge to have space for the ridiculous insulation requirements.

Years ago we raised a 5 to 12 sloped roof to 10 to 12 to create an attic bedroom. We had to scab longer rafters to the existing ones. I think we had to use metal straps to tie the raised rafters to the floor joists.

That is an option. I have had several projects wherein we popped-the-top off of a home and put in all new roof framing. This is generally cost prohibitive, but alternative roof configurations such as a gambrel roof do allow for more head room.

 

[classicT]

@ ~ @

** classicT **, ...I wonder if the existing 2 x 8 ceiling joists could be raised
and re-attached somehow.

@ ~ @

The OP is looking at creating space in the existing attic. See the image from the OP where the 5'4" and 7'9" measurements are provided. Raising the ceiling joists would reduce these heights.

Are you perhaps misdirected and thinking about raising the ceiling height in the existing main story?

 

[VirginiaCodeQuestion]

I appreciate the responses; the headroom with proper insulation is the major issue I'm running into, even with a dormer. I believe I would need R35 in the ceiling (Zone 7), but I need to double check this. If I make this insulated "Accessory Attic Space" I'm guessing a permanent staircase would be off the table due to the possibility of future owners using it as living space. Is this correct?

 

[classicT]

I appreciate the responses; the headroom with proper insulation is the major issue I'm running into, even with a dormer. I believe I would need R35 in the ceiling (Zone 7), but I need to double check this. If I make this insulated "Accessory Attic Space" I'm guessing a permanent staircase would be off the table due to the possibility of future owners using it as living space. Is this correct?

Per the Virgina Energy Code (2018 IECC), Climate Zone 7 requires a Ceiling R-value of R-49. (Table R402.1.2) You do have the option to install R-38 in the attic rafters, but it has to be full depth, including over the plates. IMHO, the AHJ BO should give you a break given that this is an existing building and accept R-38 through the attic, ignoring the full depth at the existing plate line, but that is his/her call.

VA - R402.2.1 Ceilings With Attic Spaces​

Where Section R402.1.2 requires R-38 insulation in the ceiling, installing R-30 over 100 percent of the ceiling area requiring insulation shall satisfy the requirement for R-38 wherever the full height of uncompressed R-30 insulation extends over the wall top plate at the eaves. Where Section R402.1.2 requires R-49 insulation in the ceiling, installing R-38 over 100 percent of the ceiling area requiring insulation shall satisfy the requirement for R-49 insulation wherever the full height of uncompressed R-38 insulation extends over the wall top plate at the eaves. This reduction shall not apply to the U-factor alternative approach in Section R402.1.4 and the Total UA alternative in Section R402.1.5.

 

[Paul Sweet]

Virginia is presently in climate zone 4, which requires R-49 ceiling insulation (about 15" of fiberglass or 9" of foam).

The 2021 code is scheduled to take effect in the next couple months. Several counties & cities along the NC border from the coast to Pittsylvania Co. will go into zone 3, and Highland, Bath, & Allegheny counties and the cities in them will go into zone 5.

 

[VirginiaCodeQuestion]

Thanks for the feedback. I think the only way to make this work is with a small shed dormer and closed cell insulation. I attached a new design of what I think might work and my local building department seems to think the insulation will be ok (of course I need to develop final plans and get approval). Any feedback on doing the insulation like this?

 

[bill1952]

This makes sense. I'd keep thermal barrier at roof and not down kneewalls and across ceiling. Much easier to air seal and less square footage.