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Old 04-03-2013, 12:52 AM   #1
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Blocking deck joists? Needed?


Hey fellas, I have a 16' x 54' deck at grade height. 2x10 joists 16" OC. My load beam is a few 2x10's sand which together on 6x6 posts that rest on cement sono tubes 8' deep. 5/4 deck boards. Beam is 14' from house, 2' cantalever.

Problem is deck has alot of bounce. Would adding blocking between joists help? Or maybe I need to add another beam?

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Old 04-03-2013, 01:26 AM   #2
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Blocking deck joists? Needed?


Ehh...14' span on 2x10's 16"oc is most likely going to bounce. You're at or past the limit depending on what span chart you check. Blocking most likely won't fix it - at least not completely. A center beam 7' from the house is certainly your best long-term bet. Not the easiest fix...then again the best ones usually aren't. :-)

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Old 04-03-2013, 08:21 AM   #3
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Blocking deck joists? Needed?


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Originally Posted by fetzer85 View Post
Ehh...14' span on 2x10's 16"oc is most likely going to bounce. You're at or past the limit depending on what span chart you check. Blocking most likely won't fix it - at least not completely. A center beam 7' from the house is certainly your best long-term bet. Not the easiest fix...then again the best ones usually aren't. :-)
+1 this. Another beam in the middle will do wonders.

On a side note... 8' deep footings? how/why? Not that it's a bad thing just curious why.
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Old 04-03-2013, 09:28 AM   #4
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Blocking deck joists? Needed?


sorry to hear you are having issues with your new deck.

bounce and vibration are subjective and are not considered in the building code. The building codes are concerned on if the joists will fail when loaded to live & dead loads minimums as required by the code. of course if you load the deck greater than the code requires or what the deck was designed for you will get more deflection and thus may have more bounce.

what are your deck boards made out of, composite? the 2' cantilever with a 14' back span may be at the limit for your joists depending on the grade, species and preservative treatment of the wood. What were your joists made from?

your simplest fix is a beam at mid-span as robert and fetzer said.

another issue sometimes faces with grade/ground level decks is the difficulty in ventilation under the deck. If high moisture is under the deck them the bottom of the joists will absorb moisture and expand or swell. The top of the joists tend to dry and shrink because of sunlight and ventilation. This can lead to cupping and twisting of the joists.
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Old 04-03-2013, 11:16 AM   #5
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Blocking deck joists? Needed?


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Originally Posted by robertcdf

+1 this. Another beam in the middle will do wonders.

On a side note... 8' deep footings? how/why? Not that it's a bad thing just curious why.
Yea they are deep lol. I had 8' sono tubes in back yard and when I got skid steer guy to drill he figured I was putting the 8' in there. I was just gonna cut tubes in half lol.

It is gonna be very difficult adding another beam. Ill pull a few deck boards wide by length of deck. Then I'm gonna have to build beam and use quad winch to pull it all way under deck. Ill have a few buddies help pull it up under joists, ratchet strap it up in place and use adjustable jacks on concrete blocks to lift and level it. I did this in the past on a different house and worked well. Issue with this house is my rim joists only few inches from grass.

I also have another deck off 2 storey that is built exact same. But it's 16'x16'. And about 11' off ground. 6x6 PT posts. Everything's PT. adding another beam for high up deck kinda a pain as entry door to my garage is below. Ill snap a pic.
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Old 04-03-2013, 04:13 PM   #6
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Blocking deck joists? Needed?


you may be able to sister new joists to the existing (reduces your spacing to about 8" o.c.) and would stiffen up the decks ..... just food for thought
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Old 04-03-2013, 06:14 PM   #7
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Blocking deck joists? Needed?


I do not know who designed this deck, but since it is at grade, and no clear span is necessary underneath, they wasted a hell of a lot of lumber in its construction, and did not even accomplish the desired end. They could have used 2 x 8's with another girder at 7 feet and had a lot stiffer deck, a lot smaller lumber bill, and more space under the deck. Very inefficient design.
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Old 04-03-2013, 06:22 PM   #8
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Blocking deck joists? Needed?


Well problem is my septic field runs parallel to my deck about 10' out. Field froze off last year. I had to raise grade to ledger board, about 16" - 18" in order to build a slope from deck to tree line. ( all flat here) there is alot of air movement from end to end of deck and through deck boards. I ran a sump with a French drain out from under deck to tree line.

I needed the 16" or so ontop of my septic field. I know none of this is correct way but I wouldn't get the height I needed starting at foundation of house.
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Old 04-03-2013, 06:27 PM   #9
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Blocking deck joists? Needed?


Blocking deck joists? Needed?-image-711061832.jpg

2x10 running across posts was temporary



Blocking deck joists? Needed?-image-3794606456.jpg



Blocking deck joists? Needed?-image-2282262513.jpg
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Old 04-03-2013, 09:20 PM   #10
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Blocking deck joists? Needed?


I would put two sets of blocking in there before I would try to weasel in a beam. I'm not saying it would be better, but I am saying it would be worth a try before the beam installation.

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