20X36 Northern Michigan

[jrbaxter]

I purchased the 20X30 1-story cottage plans and the "Ultimate Guide to House Framing" book you recommended. The book states that 2X6 walls are structurally strong enough for studs framed 24" on center but the plans call for 16" on center for the walls. I am modifying the plans to 20X36 using a slab foundation, otherwise no changes. I would like to frame the entire structure 24" on center, will that be adequate? Thank you,

Joe

[rick91351]

Might just be the way I learned or  .  16" centers all the way.  You really do not save all that much on your framing package.

[MountainDon]

Pluses and minuses to 24" stud spacing; from my observations and use thereof... 

It does make the overall R-value slightly greater over a 16" OC wall. Not a big difference, but in theory makes for better energy efficiency. But then a foam skin on the exterior gives a bigger boost and seals air really well too.

With 24" centers you may find the normal 1/2" drywall (if drywall gets used) can be slightly wavy in appearance; 5/8" fixes that.

Fewer spaces along a wall to mount electrical boxes to studs. A minor detail. Or kitchen cabinets... maybe use let in horizontal 2x4 to provide solid cabinet mounting.

[John Raabe]

You could certainly go to 24" framing and it can align with the roof framing or trusses. As noted you may want thicker drywall. 24" framing will be plenty strong and will somewhat reduce heat loss through the framing.

Here is a review of "advanced framing" options: http://www.greenbuildingadvisor.com/blogs/dept/musings/pros-and-cons-advanced-framing

[jrbaxter]

It's been a while since my original post and a lot has happened. We took two weeks and got the house framed, sheathed, and dried in, then had to take a couple months off. We used advanced framing technique, 2x6 walls 24" on center, 2x12 rafters aligned with the studs, 2-stud corners, single king studs with hanger brackets for headers. Even though the code made no mention of these techniques, the building inspector loved it and had no concerns. Thanks for the advice on framing!

We're getting ready to start again and I've got a couple more questions.

Is uplift a concern for a covered porch in a 90 mph wind zone? My foundation is a 4" slab, 18" above finished grade, with footings 24" below finished grade. The soil is clean sand and gravel. I'm putting a covered porch around 3 sides. My concrete contractor talked me into using 18"x6" "cookies" or "porch pads" as footings for the 6X6 beams that support the covered porch. The building inspector cautiously approved the porch pads, saying that they will work as long as they are installed correctly. As I understand it, the 6x6 posts rest on top of the footings, 24" below grade, with clean sand/gravel back-filled around the post, with nothing fastening the post to the footing. I'm sure that this is fine for distributing weight downward, but I'm concerned that it doesn't provide any uplift protection. I'm looking for input on the use of "porch pads" or "cookies" for load bearing footings, also if uplift is a concern outside the coastal hurricane zone. Thoughts?

What is the best way to tie a deck into a slab-on-grade foundation? I'm leaning toward building a floating deck that isn't attached to the foundation. My main concern is that drilling ½" holes for concrete bolts every 18" can't be good for the foundation and seems more difficult than using more porch pads.

What is the best way to provide ventilation in an airtight home in a northern climate? We're using spray-foam insulation, energy efficient doors and windows, and should have a very airtight home with no central-air system. I've read that one downside of super efficient homes is inadequate ventilation. We're trying to keep our systems as simple as possible. Our heat source is in-slab radiant, fed by a propane tank-less water heater, and a woodstove. What is the best way to ensure adequate ventilation?

Thanks,

Joe

[John Raabe]

Porch issues:
• a 90 mph wind speed will put a lot of forces on all the roofs and the porch in particular.
• I would have the same concern you do with the posts resting on "cookies" - backfilled precast pads. The only thing keeping the porch roof where it should be is the weight of the roof, the uplift friction on the porch posts from the backfill, and the roof to house connection. You can stiffen the porch roof with a bolted ledger to the house framing, brackets and/or cross bracing of the porch roof framing and a strong connection between roof and the 6x6 posts. (Are these posts treated?)
• The porch slab should be a min. 1" lower than the house slab and there should be a moisture break so that water does not wick into the house and the doors can have a proper threshold.

Ventilation:
Your fuel costs probably justify a heat recovery ventilation device for capturing heat from stale air and putting it in the fresh air. Here's an overview: http://www.popularmechanics.com/home/interior-projects/how-to/a149/1275121/. Search on HRV. You can do something simpler than what they show.

PS - Be fussy about insulation under the floor slab and at slab edges. Keep those BTUs in the house.
Radiant slabs generally cost more to heat than the calcs project. I think it's because you are putting the highest temp surface in the house and forming it into a big plate that's in contact with the ground as a heat sink. It does sound like you have soil that is well-drained gravel and sand - that will help slow the heat transfer.

[jrbaxter]

I'd like to install a Heat Recovery Ventilation system myself, but don't know how to design the system and have never installed one before. I've been around HVAC tradesmen enough to know the basics and have confidence that I can install a basic system. I was able to e-mail my plans to a radiant heat specialist who designed my in-floor radiant heat system and gave me instructions start-to-finish. Does anyone know anyone who would be able to do the same for a very basic ventilation system?

Thanks!

[John Raabe]

I would search out a local builder or HVAC installer who has experience with HRV sizing and installations. They may be able to help you get it installed right and for the best price.

[Don_P]

I do connect post to footing but usually have a cast in place footing that is larger than the cookie. Another method of providing more uplift resistance is to nail 2x pieces across the sides of the posts down low underground, then the post has to extract a cone of soil along with the post. The weight of this soil factors into the uplift resistance. We have a raised slab, I built the decks freestanding, the inboard posts are sitting on the house footings and are connected to the house foundation for lateral support. A ceiling in the porch triangularizes the roof and can provide another uplift tie.

HRV's are a great way to go for ventilation, I'm poor, we open the windows.