Replies

1. 
   DanH | Mar 29, 2015 09:16pm | #1

   What is constraining the deck?  Normally the ends would be pushed out (and the intermediate joists would similarly flex) before the decking buckled.

1. 
   ColbySea | Mar 30, 2015 05:35pm | #3

   Thanks Dan, I suspect that the end boards are constraining it.  With ebty, they have to be face screwed -- one side is against the house, so it's not moving, and the other side does look different, like it's being pushed out and down.  Surprised the screws haven't torn out there.  The ebty biscuits only have one screw between two boards. In the areas where the deck has buckled, I suspect either the screw has broken or torn out of the plastic biscuit.  The boards haven't completely separated, so I can't see the biscuit there, but it's definately a trip hazard.

2. 
   AndyEngel | Mar 30, 2015 10:26am | #2

   Is there an underlying problem?

   I've seen this issue before. That particular deck had some moisture issues below. Solving them and reinstalling the decking took care of things. You really shouldn't drain downspouts to below a deck... And a couple of inches of gravel on top of the ground interrupts the flow of ground moisture via capillary action, and can lower the RH. Of course, your deck boards may have reached their permanent moisture content, and you'll never have the issue again afer re-installation.

1. 
   ColbySea | Mar 30, 2015 05:44pm | #4

   Thanks Andy, I suspect you're right.  There are no downspouts, but the deck is at ground level and there likely isn't enough air movement.  Once I get the deck up, how much gravel should I plan to put down?  Will 1-2" suffice, or does it need to be much deeper than that.  Is there anything else that could help?  (like a permeable weed fabric, or...?)

   There is a large fir tree next to the deck so I don't want to put down plastic or otherwise 'waterproof' under the deck which might kill the tree (or cause it to topple from dead roots under the deck).

1. 
   calvin | Mar 30, 2015 07:19pm | #5

   Colby

   remember also that you are working with flooring.  In the width,  most expansion / contraction should not be constrained.  Fasteners are ok, but a solid immovable wall might not be.

   Still, I think your problem might have been decking much dryer than the ambient environment it was placed in as well as the lack of air movement.  With your material now acclimated you very well may be ok putting it back the way it was.  Personally I'd get more air circulation under it as well as spacing it from the house.

   did you flash the framing at the house or use standoffs or ?

2. 
   AndyEngel | Mar 31, 2015 10:58am | #6

   Water and wood - Imperfect together

   Calvin has good points, too. That said, with a low deck, it may not be possible to get enough air movement to make much difference. I like to use landscape fabric direction on the ground to keep the gravel and the soil from mixing over time. I don't like impermeable plastic because it kills fir trees. It also can create ponding, which I promise the local mosquitoes will love.

   Then I'd go with at least 2 in. of 3/4 in. clean stone. The trick is that water moves by capillary action only from larger pores to smaller ones. By using 3/4 stone, the spaces between the gravel will be smaller than than the spaces between the underlying soil particles, which will interrupt the capillary flow (That's one reason we use stone under concrete slabs, too). A 1 in. layer of stone might not be enough, since it could be only one stone thick in places. More is better.