Questions Answered: Deck Ledger Connections for Wood and Masonry

In this post, we follow up on our July webinar, Safer, Stronger Decks: Ledger Connections for Wood and Masonry, by answering some of the interesting questions raised by attendees.

During the webinar we discussed code-compliant ledger connection
options for both wood and masonry construction. In case you weren’t able to join our discussion, you can watch the on-demand webinar and earn PDH and CEU credits here.

As with our previous webinars, we ended with a Q&A session for the attendees. Our R&D engineers Scott Fischer and Rachel Holland answered as many as they could in the time allowed. Now we are back to recap some of the commonly asked questions and their answers, but if you’d like to see the full list, click here.

GENERAL DECK BUILDING AND CODE REQUIREMENTS

What are the drawbacks to not using a ledger and fastening hangers through siding into rim?

Testing and research has shown that if joists are not properly fastened to a ledger board that is allowed to continuously transfer gravity and lateral loads, then the connection to the supporting structure can be compromised. Per the 2018 IRC, R507.9.1, vertical loads shall be transferred to band joists with ledger in accordance with Section R507.9.1 and lateral loads shall be connected per Section R507.9.2. In addition to the structural concerns that may occur, weather proofing and flashing can cause a long-term concern and the integrity of your deck may be at risk.

The live load on page 25 shall be modified to minimum 60 psf (1.5 X 40) per code in our area on 2016 CRC and CBC?

The 2018 IRC, Table R301.5 (40 psf live for decks) and Table R507.9.1.3(1) call out the live load as 40 psf along with a deck dead load of 10 psf and a snow load of <= 40 psf.  DCA6, Table 5 has similar requirements and the same 40 psf live load and 10 psf dead load. The 2018 IBC, Table 1607.1, Item 5 does call out a 1.5 multiplier to the IRC 40 psf (1.5 x 40 = 60 psf), so if the IBC is used for decks by the building department, if it is an engineered design where the engineer follows the IBC, or if the building department imposes their own amendments and it becomes code in this part of the country, it would be a local requirement until adopted by the IRC and/or DCA6. 

Question on decks attached on a cantilevered floor — is there a special connection coming up towards the floor rim towards the ledger for decks?

The 2018 IRC Section R507.8 states that the deck must be positively anchored to the primary structure to take both vertical and lateral loads and Figure R507.9.1.3(2) references “Existing 2x Band Joist or Engineered Rim Board.” Section R507.9.1.2 also allows for 1″ x 9.5″ dimensional laminated veneer lumber. 

Additionally, the band joist of the home must bear fully on the primary structure capable of supporting all required loads. If the band or rim of the home does not meet these minimums, the building official may consider this to be unverifiable and may require a self-supported deck.

Any recommendations for home inspectors when spacing of any aspect of the ledger attachment does not meet code? DCA6?

If it is found that the ledger is adequately placed against the supporting structure and has sound contact with the home’s structural sheathing and band joist (i.e., confirm that the deck is being placed against a structure that can support the vertical and lateral loads of the deck), then adding SDWS screws to the ledger into the supporting structure may be a viable option to help make up for mis-spaced or improperly located existing lags or bolts. Load capacities and spacing minimums for this fastener are shown in our Fastening Systems catalog, C-F-2019 and in several letters and fliers, including L-F-LDGRFSTNR19 and S-F-SDWLGRTP18.

LEDGER ATTACHMENT WITH FASTENERS (LAG SCREWS, THRU-BOLTS, STRUCTURAL SCREWS)

What if the anchor bolts/screws are not staggered or are installed in pairs?

In order to install the most amount of fasteners without having an exceeding number of them be within any one continuous grain line within your wood member, staggering is necessary. Also note, a great amount of testing has been performed on these different bolt and lag screw installs — whether in conjunction with The American Wood Council, NADRA, or through several universities throughout the US. The testing has shown that the staggered spacing is the most effective installation method. 

CORROSION, FLASHING AND WEATHERPROOFING

Is this a manufacturer’s listing requirement for stainless steel? If it is within 10 miles, does that void the warranty?

The 2018 IRC, Table R507.2.3 references the distance as, “..located within 300 feet of a salt water shoreline shall be stainless steel.” However, the NADRA guide references several studies, including one done by the International Molybdenum Association titled “Stainless Steel for Coastal and Salt Corrosion” and recommends that locations within five to 10 miles of saltwater are considered at risk for chloride-related corrosion. Also, the Cedar Bureau (cedarbureau.org) recommends 316 SS within 15 miles of salt water. We recommend simply discussing the minimum requirements as set forth by your local building official to be assured that you are meeting the minimum coverage for your area.

How do we mitigate condensation moisture around the screws and the wood? We see long-term wood deterioration because of moisture (from inside the conditione space, evidently) at the screws through a membrane.

Weatherproofing as required by code is still necessary with the BVLZ install. The compression strut and ledger plate are both ZMAX®. The SDWH screw has ASTM 153, Class C HDG coating, which gives a high level of corrosion protection. Reference Simpson Strong-Tie® corrosion information at strongtie.com/corrosion.

LATERAL LOAD CONNECTION

Isn’t the tie within 24″ over ends for DTT1 ties?

The deck lateral load connection being within 24″ of the ends of the deck is required for both the DTT2Z and the DTT1Z. See 2018 IRC, R507.9.2 as well as current Simpson Strong-Tie tech bulletin T-C-DECKLAT19.

BVLZ BRICK VENEER LEDGER CONNECTOR INSTALLATION AND USE

What is the maximum gap?

The BVLZ accommodates a “gap” distance between the structural framing and the ledger from 4 3/4″ to 6 1/4″. When WSP is present, the gap between the WSP and the ledger must be between 4 1/4″ and 5 3/4″.

What keeps the compression member of the BVLZ from puncturing the rim board?

The allowable load of the BVLZ is not large enough for the compression strut to puncture a 2x rim. We have done calculations on the surface area of the compression strut’s folded end cap and tests to prove this.

What suggestions or research do you offer for attaching a ledger over one to two inches of continuous insulation?

The BVLZ can be installed when foam board insulation is present. Drill through the foam board where the compression strut will be so as to allow the compression strut to bear on structural framing.

How do you drill in at 40 degrees?

You can use a speed square to help you find the 40-degree angle. We have seen customers cut out small blocks to use as guides when drilling the holes at 40 degrees in both the masonry and the ledger. Also, the holes are oversized compared to the shaft of the SDWH screw, so if your drilling angle is off by +/- 1 degree, you can still use the self-jigging feature on the ledger plate to install the screw at the correct angle.

The post Questions Answered: Deck Ledger Connections for Wood and Masonry appeared first on Simpson Strong-Tie Structural Engineering Blog –.

from Simpson Strong-Tie Structural Engineering Blog – http://seblog.strongtie.com/2019/09/questions-answered-deck-ledger-connections-for-wood-and-masonry/