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Old 08-22-2010, 09:22 AM   #1
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#22 williedeck
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deck joist spacing and scraps
I hired a local company to construct my deck and I am extremely concerned about what he is doing and not doing. The flooring has a diagonal pattern with joist spacing of 16". My understanding is joists should be no more than 12" for diagonal patterns. Also, I noticed he is not placing 16' boards but is placing shorter and longer boards randomly without any design pattern. It appears as if he is installing "scraps" rather and it looks unatractively patched up.

This guy is fully licensed and has a crew of 5 people. All required permits have been obtained. I am not a builder. I am a home owner who contracted a professional to do the entire job so I would not have to worry about anything but pay and enjoy a safe and beautiful deck.

I signed up here becasue I do not where else to go for questions.
I have worries about the joist spacing and his usage of, what appears to me to be, scraps in some areas.

Inicidentally: the materials being used are the Evergreen composite.
Appreciate any inputs.
Thanks.


Last edited by willied; 08-22-2010 at 09:26 AM.
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Old 08-22-2010, 10:02 AM   #2
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Willie,
Pictures would help, but without that, here's some thoughts. The composite decking I have used had been the 5/4 thick and for diagonal patterns, joists were specced by the decking manufacturer to be 12" o.c. Depending on the size of the deck, if you could span the diagonal with one piece of decking, I would do that. That being said, it may create more waste, so expect to pay a bit more to compensate for more material being used. That should have been discussed up front. Also, the contractor should have provided drawings to show how the structure was going to be built. I don't know what recourse you have at this point. You may want to start with Evergreen and see what they recommend for joist spacing for your application. If it is indeed incorrect, then you need to sit down and talk to the contractor and see what can be done to fix it. If he is a professional, he should know enough to build the deck correctly. If your city inspector is sharp, he may intervene and not pass the deck until corrected, if that is necessary. Post some pics if you get a chance.
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Old 08-22-2010, 11:56 AM   #3
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First of all THANKS to firehawkmph for his reply to my orignal query. It confirms my unprofessional limited knowledge regarding joist spacing for diagonal deck boarding placement.

ADDITIONAL QUESTION:
Can joists spaced at 16" be reinforced to increase support as if they had been spaced at 12"? Can doing so reduce sagging of composite boards placed in a diagonal pattern? How should be reinforced, if so?

I am trying to find solutions to advise my contractor how to solve the problem without having to get into the hassle of asking him to tear down the 16" joists and replace them with the 12" ones. I am sure he will offer alternatives but I want to make sure his solutions will work.
Thanks.
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Old 08-22-2010, 12:45 PM   #4
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You can always add joists in between, which would make the joists 8" o/c. I'm not sure what the max spacing is, but on a 45 degree diagonal, your deck board span is 42% longer (point/point) than in the perpendicular configuration. I think you meant to cite Evergrain as the decking supplier. I looked on their webpage and they call for 16" to 24" c/c spacing for 1x6 and 2x6 boards (although they suggest reducing the span by 4" for a more rigid feel). What are you using?

The piece-part issue may be of concern. Yes, using scrap will reduce the costs, but if it comes at the cost of appearance, it may not be worth it. Is the deck 16" long and were you expecting continuous deck boards? Continuous deck boards are preferred, but not necessary. In cases where you can't get deck boards long enough, you need to stagger you splice points. Maybe this is what your contractor is doing.

I agree with hawk - post some pics.
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Old 08-22-2010, 12:52 PM   #5
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The problem is not the 16 inch spacing of the joists. The amount of load carried by each joist is determined by the area of deck supported by each joist, which is the length of the joist multiplied by the spacing of the joists multiplied by the load per square foot on the deck. The actual load on a joist has nothing to do with whether the boards are perpendicular or diagonal to the joist.

The problem with using diagonal decking is that the effective span of each piece of decking is approximately 1.4 times as much (square root of 2) times the spacing of the joist. So for joists which are 16 inch on center, the span of deck boards placed perpendicular to the joist is about 14 inches, whereas a diagonal board spans approximately 19.5 inches. The greater the span, the more stress is exerted when a person steps on the board in the middle of the deck board between the joists, which can lead to cracking of the deck board, or excessive bounce.

This problem can be solved two different ways. One way is to shorten the spacing of the joists. By cutting down to 12 inches, the effective length of a diagonal board is about 14 inches, which is about the same as if the boards were placed perpendicular. Option two is to go with a thicker deck board, i.e. 1.5 inches thick rather than 1 inch thick.

You should discuss with your contractor whether he used thicker deck boards, possibly he did. In any case, strengthening the joists does nothing unless you shorten the span of the deck boards, which is not going to happen easily. Even sistering each joist, at considerable cost and difficulty, would only reduce the deck board span about 1.5 inches, not likely to correct the problem if the deck boards are overspanned. The first step is to determine the thickness of the deck boards used, and verify with the supplier what the maximum allowable span is for that specific type of board.
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Old 08-22-2010, 03:08 PM   #6
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THANKS: WirelessG and Daniel Holtzman!!!
I hope images show the cut board/gaps. Aesthetics and function are clearly indicated in my contract, I hope I am covered. I am a retired lady and all I want is a well built deck.

My concern about stress on the boards, may have been addressed by one of the reponders (thanks)as thicker boards are being used. The label from one of the boards reads: Ever Grain by Tamko 2"x6'x16'. I guess board stress is not the problem, although the design still is.

The unatractive cuts that still concern me are in the 16' x20' part of the deck, which stand out since a diagonal pattern was used. my contract reads: "Install all decking on Diamoniad point to point until walkway" the staircase maybe?

Thus, my last question to all who read "This" is:
Will making a diamond pattern eliminate the use of these unsightly random cuts? I noticed there are still 30 2"x6'x16 boards plus other scraps laying around.
Thanks to everyone, you have been very helpful
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Old 08-22-2010, 05:11 PM   #7
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Looking at the pics, it appears that your deck is longer than 16'. If this is true, you can't get away without butting your deck boards end to end and this is not unusual on a large deck. If done correctly, the joints should not look unattractive. In your pics it looks like the framer could have taken a little more care in his cuts. What are the dimensions of your deck? Do you have a plan that you can post?

As far as the question about the diamond pattern goes, are you talking about turning some of the deck boards 45 degrees to form patterns inside the deck?
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Old 08-22-2010, 06:15 PM   #8
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Willie,
If you saw the tag that reads the boards are 2 x 6 in size, the 16" o.c. spacing should be fine. I don't know if I would start trying to create a diamond shaped pattern with the decking just to try and eliminate some splice joints. The joints could have been staggered a little better, and a couple of the joints cut a little bit tighter, but all in all, when the railings are done, it looks like you will have a nice deck. Sometimes we see the little faults and focus on them before everything is done. But you could still talk to your contractor and voice your concerns so that maybe he could make sure to be a little neater when completing the job.
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Old 08-22-2010, 11:46 PM   #9
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Thanks WirelessG and firehawkmph,
if all goes well deck will be competed iin the next 3 days. I will ask contractor to show fine craftsmanship in his cuts and joining and correct the unacceptable ones. Deck is a litle over ofver 16' but cannot determine if deck boards are being "butted" Is there an illustration I could refer to? I cannot visualize how or what it is.
I think turning some of the boards at 45 angle- see image- my previous deck.
I guess once joining is neatly done, deck will turn out fine.

As far as posting the plan it will not help. Contract description and drawing submitted to county do not match. In fact the contract ve describes in detail a lot of what is not being done. But at his point if the changes we have been discussing are implemented I will have a nice deck. I just relocated to a very rural area. For my previous deck, contractor had to submit a formal to scale drawing and a very detailed list.
If there are any comments on my last image and the layout of the boards, let me know. Mostly, I am interested in ascertaing if that style would eliminate random cuttings and create a more intersting pattern.
Thanks.
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Old 08-22-2010, 11:56 PM   #10
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Forgot to attach image for previous posting. here it is.
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Old 08-23-2010, 12:17 PM   #11
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Butted means that the deck board ends were butted up against each other and nailed to the joists - just like in your picture. The diamond pattern may or may not lead to shorter piece being added in. It all depends on how the contractor goes about it. Having butt joints as shown in your picture is not necessarily grounds for rejection. However, if he is running a 10' board, then butting it to a 2' board, and then butting to a 10' board, I would have an issue with this. At the end of the day, the important thing is that the deck boards run long and that butt joints are staggered.
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Old 08-24-2010, 06:19 AM   #12
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i agree the pattern of slices would be better if they were random like in a hrdwd floor installation but at least your using 1-1/2" material

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