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The Fine Homebuilding Podcast

Podcast 491: Above-Garage ADUs, Paper-Faced Polyiso, and Leveling Floor Joists

We hear from listeners about building your own house and the cost of electrical work before taking questions about above-garage living spaces, using paper-faced insulation behind siding, and leveling a sawn-lumber floor system.

By Andrew Zoellner, Patrick McCombe, Ian Schwandt
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      Follow the Fine Homebuilding Podcast on your favorite app. Subscribe now and don’t miss an episode:

       

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      Nat shares what he learned by building his own house. Patrick asks a follow-up question about his recalled electrical panel. Mario reminds us about leaky Canadian condos. Marks shows us his industrial-look exposed-framing basement ceiling. Kevin asks about details for an above-garage ADU. Dave wonders if he can use paper-faced polyiso for wall insulation behind board-and-batten siding. Mark needs a way to level his wavy floor joists.

       


       

      Editor Updates:

       

      • Andrew’s second-floor floor project
      • Ian’s father-in-law projects and the giant shed project
      • Jeff’s playing in the shop
      • Patrick’s chainsaw chain sharpening (Newtown Power Equipment) and heating system replacement Heat pump rebates

      Ian's giant shed Ian's giant shed

       


      Listener Feedback 1:

       

      Nat writes: Hey Patrick, Hope you had a nice week. I got to listen to the manual labor and dream houses aftershows and, as always, they were wonderful both from an information and entertainment standpoint. A lot of great information in there that is certainly tangential to the owner-builder conversation. I know you didn’t ask for it, and please feel free to ignore it, but here is what I would have liked to hear a couple years ago when we started down the road of building our home (the bullet points):
      1. Plan everything— from the broad-spectrum site planning to the minute details of air sealing and flashing, to insurance and financing, go in with a plan. It is easy to think that as the owner builder you will be immune to change orders, but they will still cost time and money.
      2. Figure out your “value add” early- do you like manual labor? Are you a people person with management skills? What is your hard skill set? What are your soft skills? What do you enjoy? How can you avoid burnout?
      3. It is going to take longer than expected, even if you plan for it taking longer than expected, especially if it is your first time.
      4. It will probably cost more money than expected.
      5. Consider the cost on your lifestyle and your relationships: this could be the best experience of your life…or the worst…or more likely a roller coaster ride in between.
      I will leave it at that and also apologize for the unsolicited suggestions. Did you come up with any ideas for best practice floor reclamation?

      Related Links:

      • The Self-Designer/Builder: The System is Not Built to Serve You
      • Building a New House
      • Ok, So How Much Does Building Your Own Home Cost?

       


      Listener Feedback 2:

       

      Patrick writes:  Thanks again for the airtime last week and if possible, email me back with your new response after seeing this estimate.

      Question…would the fact that we have wires in the crawl space and attic going to this sub panel make the price more expensive? I guess it would…

      Comment…it’s been like pulling teeth to get an electrician out to our house, so I feel like I just want to go with these guys and not worry with another estimate. Also, our usual electrical company recently quit doing residential work and now does new apartments and new commercial only. What a bummer! I honestly have no clue if this seems high (the portion dealing with the sub panel removal).

      Thanks again for your time and knowledge,
      Patrick!
      P.S. Please don’t mention the electrical company on the air. I don’t think y’all would but you know…y’all are professionals!!

       


       

      Listener Feedback 3:

       

      Mario writes: Hi guys. I grew up in British Columbia (90’s) and recall a huge “Leaky Condo” issue in the Vancouver area which led the government to implement a lot of red tape to the industry (mainly an expensive insurance program for contractors doing new builds ostensibly to cover problems down the road but actually it only paid for the bureaucracy). As a new apprentice I framed one house where the client agreed to be “contractor “ to get around the multi thousand dollar expense my boss would have had to pay for the privilege of being a contractor. My suspicion is this self-builder testing came about as many people were using the same workaround.

      Now in Newfoundland, Mario

       


      Listener Feedback 4:

       

      Mark writes: Hi Patrick, In show 483 you discussed basement ceiling options in the context of maintaining access to junction boxes and utilities. I have a solution that maintains utility access that has worked well for me. I mounted gypsum panels in between floor joist using cleats. I placed acoustical high density insulation above the gypsum panels to help control sound transmission through the ceiling/ floor. I used exposed spiral ductwork which compliments the industrial look of the space. The utilities, joist and panels are all painted the same color. I’ve been here two years now and no issues with dust or spider webs in the joist. I have access above the panels to run wires for speakers, power and lighting as needed. I’ve enclosed a few photos of the finished basement. I’m not a fan of acoustical tile ceilings and a gyp ceiling would have made future access difficult and made the space tighter with soffits and lots of access panels.
      The industrial light over the pool table is my latest project. I built it from scratch based on a light fixture I saw online.
      Love the podcast, Mark
      (HVAC myth debunker) DIY’er

      MARK'S BASEMENT
      MARK'S BASEMENT
      MARK'S BASEMENT
      MARK'S BASEMENT
      MARK'S BASEMENT

       

      Related Links:

      • Soundproofing a Floor With A Wood Ceiling Below

       


      Question 1: What are my insulation and roof options for an ADU above a garage?

       

      Kevin writes: Here is my question regarding ADU design:
      We moved to Vermont a few years back. Our family is not in New England. Our parents are retired and want to stay for longer visits and spend time with the grand kids. They also want a little privacy and comfort when they are here. My wife and I are planning a mother-in-law suite over a garage. This would provide us with more vehicle/tool/machine space and an above area for our guests.
      1) The building is planned to be a simple cape style with a shed dormer. From what I see, pretty standard. My wife hates shed dormers. Any ideas for simple designs that don’t include shed dormers? Also, with aging parents, any ideas on making the accessibility better than an interior or exterior stairway?
      2) I understand the garage space and ADU need to have a solid air and fire barrier between them for safety reasons. With 2 leaky garage doors- is there a reason to go crazy on the garage portion insulation? Can I do 2×4 construction on the garage portion and then switch to 2×6 on the gable ends of the living space portion? Can I put rigid insulation between the bottom of the joists and the drywall- this would add to the insulation and be an additional air barrier. The remainder of the floor joist space would be cellulose or fiberglass.
      3) I was hoping to avoid some sheathing (Issue 309 by Fernando Ruiz: How to Get Sturdy Walls Without OSB), but he still applied sheathing on critical walls and gables. If I did that I would still end up applying sheathing around the garage doors and the two gable ends. This would more or less make the non-sheathed areas minimal and I might as well sheath the whole thing for simplicity. Thoughts?
      4) I am planning a cathedral ceiling with I-joist rafters. Vented using baffles. Insulated using cellulose.
      5) There’s room to play with the exterior grade. Is a FPSF doable? I can ramp the grade for the garage entry but also keep the grade down around the rest of the building. Or is it better to do a traditional footer that keeps the garage slab 8″ below the walls?

      Related Links:

      • Designing Garages With Living Spaces Above
      • An Over-Garage In-Law Suite With a Wealth of Storage

       

      Question 2: Will the rigid paper-faced polyiso insulation I plan to use for the exterior of my barn get moldy?

       

      Dave writes: Hi Patrick! Love the podcast and the topics you cover. I was able to salvage about 100 pieces of 2” thick rigid paper-faced poly iso. I would like to fasten this to the exterior of my barn for insulation, but I’m concerned that the paper face will mold. What do you think? The planned assembly would be 2×4 stud, 5/8 plywood, 2” rigid paper faced poly iso, wrb, furring to create an air gap, vertical rough sawn board and batten siding. My thought is that the wrb would stop moisture from getting to the paper faced poly iso and prevent it from getting moldy, but would love to hear what you think. Bad idea?
      Thanks for any insight!

      Related Links:

      • Patrick’s Barn: Oh Boy! Mountains of Polyiso Insulation
      • Get the Right Rigid Foam

       

      Question 3: How do I even out my floor and how should I approach sealing soffit vents?

       

      marc's-main-floor-beam
      Marc writes: Hello! I love the show, thanks for everything you guys do. I have two questions.
      1. My house is a 1952 built ranch, very simple. I have a basement. My main floor has some “unevenness” to it in some areas right next to where the main floor beam runs down the center of the house under the floor. The floor joists that attach to it are done so with an older method: a ledger strip and each joist has a 2×2 notch cut out of the bottom. Some of the joists have some separation and I suspect that if I tighten the connection back up and fortify it, I can straighten my floors out (to an extent, the wood obviously has shrunken/shifted over the years).
      What do you think the best course of action would be? I could either remove the ledger strip and install joist hangers OR get some nice big truss screws (ledgerlok? Trusslok?) and run them up and through the joist into the girder it hangs from. Otherwise, the joists seem to have just a few toenails. If I remove the ledger strip, I’d have an issue still with the joist hangar and the notch under the joist where the ledger strip was.
      2. I just picked up a really neat tool that Klein Tools came out with – the iOS Thermal Imager. It attaches to my phone (comes in android version too) and I did a quick “energy audit” on my house. One of the problem areas is the backside of my house that was an addition. It has a 3/12 pitch roof with no attic space and open soffits were installed. Air just flows up through the soffit vent, between the rafters over the top plate and bleeds into the house. I’d like to seal that opening above the top plate. How would you approach this?
      I attached a picture of one of the floor joists from the basement for reference. This one doesn’t have a very big gap but others are worse.

      Related Links:

      • Bostitch Strapshot
      • Should I Close My Attic Gable Vents?
      • Air-Seal an Attic Series: Sealing Soffits and Chases

       


       

      END NOTES:

       

      Members-only Aftershow Podcast 491: Patrick, Ian, and Andrew discuss Ian’s new storage outbuilding. He describes the construction details and finishes he’s planning, and the group talks about why he made the choices he did. They also discuss ways of building out living space once the shell is complete.

      Podcast 491: Members-only Aftershow

       


       

       

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      This episode of the Fine Homebuilding podcast is brought to you by Andersen Windows.

       

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