Deck Joists question?

[Steve]

I'm building a deck (1st time building a deck) using cement deck blocks for support (21 blocks). Deck is 10' x 12' on the side of a AG pool. Each joist is supported by 3 - 4"x4"s set in the deck blocks. Eack 4"x4" has to be cut to fit due to uneven ground.

I have 4 joists in place now and I notice they arent perfectly even with each other. I was using a 2' level to set the hight as I was putting them in. When I stretch a string across all the joists I can see a variation of up to .125" from joist to joist. I could go back and shim under some of the joist but I was wondering how much differance it will make?

Will this variation be noticable when the 5/4 PT decking is screwed down??

Also, Do you have to screw the decking down at every joist? Can you screw down the decking at every other joist then alternate with the next board??

Thanks for any advice!

Steve

[YesMaam27577]

I'll take the last question first. Yes, you should fasten the decking to every joist. (No exceptions.)

The uneven joists may be an issue. The average person can see a deflection of an eighth of an inch, and your feet will fell it too. But it depends on how small of a span the .125 difference occurrs within. If there is a gradual slope of a total of .125 over a distance of six or eight feet, then no one will notice.

If the .125 difference is between two adjacent joists, then I'd fix it before I decked it.

[Pop]

The.125 is between adjacent joists. 16" on center. I was thinking the same thing but having never built a deck I was wondering how accurately aligned the joists are on the average deck.

Seems like it would be easier if it was a conventional deck and I could use joist hangers.

I'll fix the 4 joists before I move on to the next 5. Thanks for the opinions!!!

Steve

[gg]

[amder]

[Pop]

Good points about the moisture content changing the wood. Now that I think of it, My brother in law used this same support system last year and in the winter all the blocks shifted up and down slightly. He figured he would shim the posts in the spring. When spring came around the blocks had returned to there original position (frost heaving?) So I guess 1/8" probably wont matter.

Thanks

Steve

[Carpenter Ant]

How is it possible to get the joists in line if there is a joist with a bad crown?

[McQualude]

gg spaketh...

.125 = 1/8" easily measurable with a tape, even a yard stick