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Home Inspector: New building code rules for decks in Minnesota

As I mentioned in a blog post at the beginning of this year, Minnesota adopted a new building code on January 24th. I covered a few of the most significant changes, but one of the bigger changes that I never talked about is the addition of a whole section on deck construction. I decided to wait until May to cover the stuff on decks, because the North American Deck and Railing Association says May is Deck Safety Month®, and they've partnered up with ASHI to promote deck inspections by ASHI Certified Inspectors.

There has never been much in the Minnesota State Building Code specific to decks, but now there is. Just browse to section 507 of the 2015 Minnesota Residential Building Code to see it all. It's not much, but it's a lot more than what we used to have.

Chapter 5 of the Minnesota State Building Code can be viewed online here http://codes.iccsafe.org/app/book/content/2015_Minnesota/Residential/Chapter%205.html, but that's as good as of link as I can give.  You need to scroll down a ways to get to section 507, and none of the text at that page can be copied. To navigate directly to section 507 of the 2012 IRC, which is exactly what Minnesota uses, click this link instead: http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_5_sec007.html. The text there can also be copied and pasted, which I feel is nice.

If you want an excellent document that explains how to build a deck that conforms to the 2012 IRC, download the free Prescriptive Residential Wood Deck Construction Guide, based on the 2012 International Residential Code. Anyone who inspects or builds decks ought to have a copy of this document, and have it available on their smartphone or tablet at all times. It's great.

Here are the two biggest deck requirements that stuck out to me:

New lateral load connection requirement

As far as I'm concerned, this is the biggest change that deck builders will now be required to make in Minnesota. In section R507.1, the code says "Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads." Then in section R507.2.3, the code says "The lateral load connection required by Section R507.1 shall be permitted to be in accordance with Figure R507.2.3. Where the lateral load connection is provided in accordance with Figure R507.2.3, hold-down tension devices shall be installed in not less than two locations per deck, and each device shall have an allowable stress design capacity of not less than 1500 pounds (6672 N)"

The diagram below shows figure R507.2.3, but I colored the lateral load connection device that they're referring to orange: Lateral Load Connection Device This is just one type of lateral load connection device, and this specific device doesn't need to be used. They're just showing one example of a device that could be used. While effective, this particular device would be especially difficult to install, because it would require a lot of access to the framing inside the home, and would also require the building official to have to verify that the floor sheathing was nailed at 6" maximum on center. How in the world is the building official supposed to do that on an existing home? Rip up the flooring? I think not.

I've never actually seen one of these devices installed, and I don't expect to ever see one. There's a much simpler device out there that meets the requirements of the 2015 IRC, called a Deck Tension Tie, made by Simpson Strong-Tie. Check it out:

DTT1 Diagrams

These devices have an allowable stress design capacity of not less than 750 lbs each, so at least four of these devices would need to be installed on every deck. These aren't specifically approved by the Minnesota State Building Code*, but if it's good enough for the 2015 IRC, it ought to be good enough for us. More on that topic here: Installation Options for Deck Lateral Load Connections. I've heard a rumor that building officials throughout Minnesota are allowing these things, but it's always wise to ask first. The Journal of Light Construction just posted a little blurb about these on their web site, along with a great cut-away photo showing one being installed: http://www.jlconline.com/framing/simpson-strong-tie-dtt1z-deck-tension-tie_s.aspx

No more nonsense on deck ledger connections

Section R507.2.2 says "Girders supporting deck joists shall not be supported on deck ledgers or band joists." The photo below shows what this means.

No girders supported from ledgerboard

Also under R507.2.2, it says Deck ledgers shall not be supported on stone or masonry veneer. The deck construction guide that I referenced above has slightly different wording on that topic, but I think the intent is the same; check out their diagram below:

Deck Attached through brick veneer

Just in case their diagram doesn't make it clear, here are a couple of photos of my own, showing what not to do:

No deck attachment through brick veneer

No deck attachment through stone veneer

The fix for all of these situations shown above would be to have the deck be self-supporting. In other words, it wouldn't rely on the house for support.

Most products aren't specifically approved by the building code.  More on that topic in last week's blog post: Are Diamond Pier footings approved for decks in Minnesota? Answers from the 20 largest cities.

Author: Reuben SaltzmanStructure Tech Home Inspections

          

Home Inspector: Are Diamond Pier footings approved in your city?

Diamond Pier Footing Approved

Last week I posted an update on Diamond Pier footings, and since then I've had a number of people ask me whether or not Diamond Pier footings are approved for use in this city or that city. The best way to get the most accurate, up-to-date answer to that question is to contact the building inspections department for the specific city and ask.

Why can't this information be quickly looked up? Because the Minnesota State Building Code does not specifically allow the use of Diamond Pier footings. There are a bazillion products that the building code doesn't specifically allow. That doesn't mean they can't be used, but the building official needs to give permission to use them. That's why plans need to be submitted to the building official before work is started. Section 1300.0110, Subpart 13 of the Minnesota State Building Code says:

Subp. 13.  Alternative materials, design, and methods of construction and equipment.

The code is not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by the code, provided that any alternative has been approved. An alternative material, design, or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the code, and that the material, method, or work offered is, for the purpose intended, at least the equivalent of that prescribed in the code in quality, strength, effectiveness, fire resistance, durability, and safety. The details of any action granting approval of an alternate shall be recorded and entered in the files of the Department of Building Safety.

So, do Diamond Pier footings comply with the intent of the code? Are they at least the equivalent of that prescribed by the code in quality, strength, effectiveness, etc? For a manufacturer to prove that their product meets the intent of the building code, they get an ICC-ES report. It's a report designed for building code officials to use to help determine if a product meets code, and it tell the building code official exactly how a product is supposed to be installed. In fact, the instructions in the ICC-ES report actually supersede the manufacturer's installation instructions. If you're building a deck, a few components on the deck that may need an ICC-ES report are the composite deck boards, the aluminum guardrails, the structural wood screws used to fasten the ledgerboard to the house, the joist hangers, and the lateral load connectors. Diamond Pier footings have an ICC-ES report too, which can be viewed here: ESR-1895.

As long as the building official determines that Diamond Piers meet the intent of the code, they shall approve their use. So, getting back to the question at hand: are Diamond Pier footings allowed for decks in <insert city>? I called the building inspections departments at the twenty largest cities in Minnesota to find out. Here's what they said:

Apple Valley yes
Blaine yes
Bloomington yes
Brooklyn Park no
Burnsville yes
Coon Rapids yes
Duluth no, because "they have not been state approved".
Eagan yes
Eden Prairie yes, need to use DP75 footings
Edina yes
Golden Valley* yes… but they require a test hole to be dug first, as well as a site inspection.
Lakeville yes
Mankato yes
Maple Grove yes
Minneapolis yes
Minnetonka yes
New Hope* yes
Plymouth yes
Rochester yes, case by case basis
Saint Paul yes
St. Cloud yes
St. Louis Park no
Woodbury yes
* Not one of the 20 largest cities, but included in this list anyways.

So there you have it. Of course, by the time you read this, the answers might change. If you have any specific questions about the answers given, contact the building inspections department at that city.

For more information on code approval of Diamond Pier footings in Minnesota, check out Diamond Pier's discussion of this topic on their web site: Code Compliance Information for Diamond Pier® Foundations in the State of Minnesota.

Post update 5/21/15: I received an email from a reader last night asking for a link to an independent study or data showing how this product works and performs.  I've posted all of these links already, but perhaps it would be helpful to have them all in one place.  Here they are:

Author: Reuben SaltzmanStructure Tech Home Inspections

          

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