Elijah

October 2020

Converesation with Elijah Pearce, architect.

• Sears house - that was legit
• Microhouses - can't sell that for money afterwards
• Selling this after you are done - that is a serious proposition.
• So going legit is a big deal.
• Katrina Cottage - https://www.mariannecusato.com/. Full set of docs for construction. Set of plans is step 1.
• But - regulatory - and the general contractor part of the enterprise. She delivered something for a contractor, not a person.

September 2020

Catarina and Marcin,

Sorry for the lengthy email. This one little detail has a lot to it. I've put my thoughts below about the two options, as well as thrown out a possible third route.

Thoughts on Option 1 (offset sheathing): - I like getting a better connection between panels. Not only would you have the top plate of your double top plate tying the individual panels together, with this offset strategy you have the sheathing bridging two panels together. Aside from the structural benefits, I would imagine this would help with alignment of the individual panels and more uniform exterior plane. -Also, I like creating a more circuitous path for water, with the joint of the plywood now offset from the joint in the housewrap. -I see the major downside of this option being that it doesn't seem to allow you to tape that vertical lap in the housewrap. While the code only dictates a 6" lap, this is in regards to "No. 15 asphalt felt" (tar or building paper). Housewrap, which I agree is a superior material, is technically an "other approved water-resistive barrier". Housewrap, is of course, basically universally approved, but typically each manufacturer has an ICC report showing how their proprietary material meets/exceeds the performance of No 14. asphalt felt. The issue is that in their ICC reports, there is typically a statement that installation must meet manufacturer's written instructions. So in a slightly convoluted way, to meet code, you must meet the manufacturer's written installation instructions. Many will require a taped vertical seam, even with a 6" overlap. See Tyvek (https://www.dupont.com/content/dam/dupont/amer/us/en/performance-building-solutions/public/documents/en/K16282-Residential-WRB-Install.pdf) for example. I also took a look at Kimberly-Clark's Block-It, which is what I believe you are using now. They do not have a taping requirement :) ....but do require a 12" overlap at vertical joints :( .(https://www.kcprofessional.com/Umbraco/media/278855555/blockitinstructionsheetpdf.pdf). Would a code official really call you on that? Maybe/maybe not? Aside from the code issue, a taped joint really would be preferable.

Thoughts on Option 2 (double sided tape) - I like this as it seems to meet the letter, if not typical intent, of the code. This may make it an easier sell across different jurisdictions. - My main concern with this option is how to deal with the resulting flaps. Can you roll/fold the flaps neatly enough to lay the batten tightly against the exterior sheathing? Also, I would expect the batten's nails would have to penetrate the rolled/folded portion of the house wrap. One nail would make several holes through the stacked wrap. -One addition to this option would be to add a layer of self adhered waterproof (SAWP) membrane overtop the entire length of the joint. Most manufacturers have a "tape" version of SAWP membrane that comes in 4" or 6" rolls. If a layer of this was added over the roll/folds of the housewrap, it may help keep everything in place as well as provide extra protection for the batten nailing. Self adhered flashings have a self-sealing property that can close around nails/staples in a way that house wrap cannot do.

I also sent this conundrum out to a Tyvek rep that we've worked with before. He sent me their recommended installation for panelized walls (see attached). If you are willing to install the exterior sheathing after the walls are erected things get a bit simpler and mainstream details will apply. However, I understand that this may defeat the purpose of a fully pre-built solution.

Aside from your two options, I wanted to throw out a third route. Rather than treat the joints between the panels as typical wall and attempt to lay the WRB down in a typical code compliant fashion, what if you approached these as truly independent panels but sealed together? I was thinking about sliding glass doors. These have a gasket system at the door jambs and a weeped threshold at the sill. The attached options are all a play on that theme. While I think these options follow general principles of good flashing design -- have I ever used or seen a detail quite like this? -- no. These would be quite the experiment. In a typical architecture firm, you try pretty hard to avoid experiments. Generally you want to shoot for something that somebody else has tried and worked the kinks out over the years. That being said, what you are doing is much more exciting! I would just recommend testing out whatever route you choose as much and thoroughly as you possibly can. Codes and installation requirements are generally written by the pile of failures spanning decades. Buildings fail a lot. New ideas don't have the benefit of those years of trial and error. But if you can do mock ups, blower door tests, hose tests and anything else that makes sense - you might be able to preempt some of the worse potential problems.

Finally, a few thoughts on permitting/inspections. Anytime you stray from the standard code compliance path there is a risk of a zealous plan checker or inspector pushing back and causing some problems. I think any of these options run that risk, but a well researched argument can often win the day. I would just be prepared to have to do a bit of defending when presenting this building to any building department.

Ok well I hope this may help. Do let me know if there is anything else where I might be of assistance.

Thanks, Elijah

Q&A

What if we use double-sided tap stuck on to the underlying panel?

--- If you can physically do this, this is probably the most straightforward solution. I was just imagining you needing to drop the panels down over the anchor bolts -- making taping that side awfully hard. But if you can get double sided tape on that side (tilt the panels in, or slot holes perpendicular to the foundation?)...I think this is a winner. Less complicated and it would be hard to say that it doesn't meet code.

Hmmm, maybe we need to go to Tyvek. But how do we find out exactly if we will pass? Does this mean talking to building officials in specific locations? Do they typically take that type of question, or do they brush you away and tell you to bring an architect/engineer stamp?

--- Unfortunately it really varies by jurisdiction. Some building officials are super helpful, some are less so. Some may want you to submit plans before they will get into details with you.