Decking expansion problem?

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Old 03-14-15, 07:17 AM
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Decking expansion problem?

Hi everyone! I'm new here and very glad to have found this forum. I live 75 miles east of Toronto and am just starting to thaw out .

I built a 16 ' by 32' deck four years ago using Elk decking, which is a man-made product consisting of oak and polypropylene (I'm unsure of the ratio). I laid the decking with the recommended non-toothed clips and encased both ends of the deck with a decorative rim joist.

The hand rail is face mounted on the rim joist. Problem: the railing is tipped outward about two inches on the top. Underneath, you can see where the end joist is pushed outward. To clarify, I supported the decking with 2x8 PT joists, and then mounted the 2x10 rim joists over (lag bolted from behind to hide the fasteners) the 2x8 joists. I did this to hide the end holes in the decking. I fear this method has caused the railing to tip outward due to the deck expanding in the freeze-thaw cycle.

I could remove the rim joist so the deck ends have room to expand, rip some sort of decorative cap for the deck board ends, and then use a deck mounted railing. The complication is, I use four 4x4 posts to support a non-waterproof wooden shade structure. The 4x4 posts are bolted to the rim joist and railing for support. So my questions are:

- Do you think it's the freeze-thaw cycle that's causing the railing to tip out?
- Is there a way I can fix this without modifying the existing design?

Perhaps I need to post a diagram of my problem before you can answer? At any rate, many thanks for the help!

- Lee
 
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Old 03-14-15, 07:26 AM
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Welcome to the forums!

Material contracts during the freeze cycle and expands during the heating cycle which would be opposite of what you have witnessed. I think it is the use of lag bolts as opposed to carriage bolts that is your issue along with the fact that you screwed from behind. The board you are attempting to support is only partially penetrated by lag bolt which won't give it any strength.

http://www.doityourself.com/forum/el...rt-images.html

I'm sure we can come up with a good solution that will hide the proper fasteners.
 
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Old 03-14-15, 07:59 AM
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Thanks for the quick reply, czizzi!

You make perfect sense. The deck is on the south side of my house where it gets tremendous deck surface heat even during moderate summer days (worse during a heat wave). As for the lag bolts, you're probably right--there's not much "bite" into a 1.5 inch thick board. I should mention, the 2x8 support joist and 2x10 rim joist are still well connected. It's the pair of them that are moving together. I even laddered or bridged the outer 2x8 to the next 2x8, 16 inches in. perhaps I should draw a picture and post it. Again, thanks for the information.

- Lee
 
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Old 03-14-15, 08:17 AM
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Here's a diagram of the deck. Sorry, I don't know how to delete the first picture .
 
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Old 03-14-15, 08:22 AM
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Here's a diagram of what's happening.
 
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Old 03-14-15, 08:35 AM
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Can you post a real picture instead of the diagrams?
 
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Old 03-14-15, 09:47 AM
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I can try. It's a bit damp here today, however, I'll give it a shot (no pun intended )
 
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Old 03-14-15, 10:14 AM
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That design would never pass inspection here.
Where required to notch the post so the rim joist are fully supported by the notch.
The rim joist need to be through bolted, (you can counter bore where the bolt heads are so they sit flush.
Rail post should have been mounted on the inside and blocked so there supported in all directions.
deck rail post framing detail - Bing Images
You did use joist hangers, right.
Is there a center beam to break up that 16' run of 2 X 8's I hope.
 
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Old 03-15-15, 07:02 AM
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Hi Joecaption1

I guess building codes are like socks--they come in all sizes and shapes. My railing 4x4 posts are double-bolted (carriage bolts) through the rim joist and 2x8 floor joist. I have built 5 such decks in my area, which were passed by the inspector. The posts were surface mounted to the rim joist. The vertical support posts for the shade roof are notched, double bolted, and rest on the rim joist. All the floor joists are bridged over the 16 foot span as per Elk decking requirements. There are two support beams, each triple 2x8 and spaced about 7' 6" on center. The deck cantilever is 2’—the maximum allowable under our code.

Back to my problem. For the other decks I built, I used either cedar or pressure treated flooring. For one, I used Trex decking, which has a more “solid” surface and is more resistant to water penetration. It has no issues. It’s my own that is having the issue of deck board expansion. The Elk decking has a dull finish and tends to soak up a lot of water. A friend used it for a deck on the north side of his house and eventually replaced the Elk decking due to continuous mold and moss problems. To me, that's a moisture issue. Water that freezes tends to expand. My design may lack in a few areas, however, I think the decking has a lot to do with the failure.
 
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Old 03-15-15, 08:11 AM
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If it was expansion, then in theory, all your 2x8's would be rolled over in the same manner stretching toward the perimeter. Can you get under the deck to put a speed level on each joists to verify?

Also, it appears that issues with Elk Decking are fairly common. Here in the U.S. there there is a class action lawsuit against GAF who formerly made the now discontinued product. However, I do not know if a similar lawsuit has been filed in Canada. Might be worth and investigation and is also reason for your issues over and above deck design and construction. https://www.google.com/search?q=elk+...utf-8&oe=utf-8
 
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Old 03-16-15, 08:31 AM
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I can check the level of the joists. They appear all right. The deck is about 4 feet above grade. I was thinking the deck board expansion wouldn't push the internal joists off level because they are all attached by bridging, and the actual pressure point is at the top. The outer two joists are being pushed at the top because they aren't attached to anything, that is, they have nothing supporting them. The clips used to hold the decking down are toothless. I know Trex decking uses a toothed clip, which likely prevents a lot of the lateral movement.

I was unaware that Elk had a lawsuit against them--no big surprise. I've heard nothing here in Canada about that.

Iím starting to think my best option is to get rid of this crappy product and replace it with Trex. I seem to be going through a lot of this lately. A few years ago, I finally got action from ICO shingles to replace my Renaissance II shingles. I know there was a huge class action law suit against ICO in both the U.S. and Canada.

Thanks for all your help!
 
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