Ask NADRA: Tilting Support Posts

February 3, 2012 |

My deck is supported by wood posts that rest on concrete piles set into the ground. The concrete piles seem to be moving causing a tilt to the wooden post (inward, toward the house). Do you have a guideline on how much post tilt is acceptable?

Glenn Mathewson, NADRA’s Technical Advisor, responds:

I can understand your concern and I’m glad you contacted NADRA for assistance. From what you have described, it does not reflect an appropriate foundation system. All foundations, including those for decks, must be placed a minimum of 12 inches below undisturbed soil. That refers to soil that has not been backfilled, rototilled, installed with sod, or any other disturbance. In a common yard the pier would be at least 18” below the top of the final grade. This depth provides lateral resistance to overturning… what your piers are likely doing. I presume insufficient depth of the piers is the source of this problem.

As for the posts, I can’t really recommend any acceptable tilt other than the tolerances in the bubble on a 4-foot level. I would presume that if the posts moved from vertical to tilted, then they’re likely to keep moving. That is a more significant issue than just a little angle on the post.

For the sake of discussion, a deck “could” be designed with a tremendous angle in the posts. For the sake of your deck, I would look at shoring it up and replacing the piers. If your posts are in good shape, you could even pour your piers a few inches higher than before; level the deck out nicely and then cut the posts back in at just the right height.

If your feeling up to it, grab a buddy or two, a weekend or two, and the right tools for the job, otherwise, take a look at our member directory and find a NADRA builder nearby. Either way… we wish you the best for you and your deck.

Thank you for contacting NADRA.

Glenn Mathewson
NADRA Technical Advisor

Ask NADRA: Deck Ventilation Requirements

April 30, 2011 | Ken from Orangeburg, SC asks:

“I am wondering is there a minimum height requirement for a
deck to allow for adequate ventilation under the deck. Is this
measured to the top or bottom of the decking timber?”

Glenn Mathewson, NADRA’s Technical Advisor, responds:

Hello Mr. Panitt.

Thank you for turning to NADRA with your questions about the Decking and Railing Industry. We are certainly happy to provide you guidance. The International Residential Code (IRC) and International Building Code (IBC) do not specifically regulate the ventilation of areas underneath exterior decks. IRC Section R408.1 describes the ventilation requirements for under floor spaces, including the minimum net free area, but it is in reference to areas under buildings that are enclosed by foundation walls. While it would certainly be good practice to maintain moisture control under decks that are very low to the ground, its not part of the minimum standard set forth by the IRC. However, in the case of manufactured decking or other products, the installation requirements of the manufacturer are essentially part of the code. This may be from a direct reference to, such as section R317.4.1 in the 09 IRC for wood/plastic composites or through approval as an “alternative”.
I know at least two prominent tongue-and-groove composite decking products that require a minimum height above grade to make up for the lack of air flow between the boards. In both cases the distance was 12 inches of vertical space beneath the bottom of the framing, though the percentage of perimeter where it was required varied. You must always adhere to manufacturer’s installation instructions, not only for good practice, but also for code compliance.
For spaced deck boards, the gaps would likely suffice for ventilation. They may be narrow, but they’re evenly dispersed. One thing to consider, however, is the size of the gaps and the material used. If swelling of wood, expansion of thermoplastics, proximity to heavy autumn leaf fall, long snow coverage or poor maintenance/cleaning is likely, the gaps may close. In that case, additional ventilation openings or greater clearance to grade would be a good plan.

I hope this information is of assistance to you and the visitors of the NADRA blog.

Sincerely,

Glenn Mathewson, MCP

NADRA Launches First-Ever Industry Event!

Quakertown, PA – March 30, 2011 | Understanding the Existing Structure was launched on March 24th, 2011 at The Biltmore in Providence, Rhode Island. This course is one of a four-part series designed to help contractors prepare for their NADRA MDB* Certification exams. (Master Deck Builder)

Over 75 Industry professionals gathered the evening before the big day of education for a networking dinner on the 17th floor of the historic Biltmore hotel. About 40 of those attendees were from NADRA’s very own New England Chapter. Fred Aldrich, NE Chapter President states “It is truly an exciting time in our industry and the NADRA events in Providence are a great example of that excitement.”

With sponsors like Fiberon & TimberTech who are willing to support the Association on these ground level programs, NADRA has been able to bring first-ever events to the industry, such as the annual meeting and cocktail reception, industry deck awards, and now the first-ever industry Certification for Deck Builders along with the new Factory Trained programs that others are sure to follow! Tony Groh, Northeast Regional Sales Manager, TimberTech states, “I was very impressed with the NADRA event in Providence. The quality of the NADRA member contractors is very evident. It is refreshing to participate in presentations where the audience is so engaged and the questions so insightful. It was obvious that those present are on a continuous quest to improve their craft. We look forward to the next NADRA event.”
Continue reading “NADRA Launches First-Ever Industry Event!”

Ask NADRA: Deck Stair Lighting Codes

March 21, 2011 | Lainie Sleppin of Mid-State Lumber asks:

“I am getting a number of calls regarding the code on deck stair
lighting, no pun but can you shed any light on this code so I can
advise correctly. We are talking about guys in the NJ market.

Thanks for your help and have a great weekend.”

Glenn Mathewson, NADRA’s Technical Advisor, responds:

Hello Lainie,

Thanks for your confidence in NADRA, the voice of the decking industry, to be your “go to” when you need quality information on the decking and railing industry. I understand your contractor customers in the New York and New Jersey area have been asking questions lately about lighting at deck stairways. I am happy to provide you assistance in better understanding the requirements of the 2009 IRC in this regard. Many people I discuss this with are surprised that when you read Section R303.6 there are two requirements…one for the location of a lighting fixture, and one for the illumination of the stairway. They are not one in the same.

I have copied below the discussion from ICC’s deck code book, Deck Construction based on the 2009 IRC. Continue reading “Ask NADRA: Deck Stair Lighting Codes”