Uneven Joist height


Old 08-01-12, 08:39 PM
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Uneven Joist height


I am well underway on my deck frame, it's almost complete. This is a big project for my first deck.

I have a few concerns as I'm not sure if this will make or break the deck.

I did my best to level out the joists and install them crown up, but obviously some joists are taller and crowned differently. Overall the deck is levelled, and slightly slopped appropriately for rain run off, but I want to be sure that the deck boards will be installed straight.

Even though this is my first deck, I'm contemplating using Ipe, and since Ipe is dense and hard, I"m not sure if it will bend to lay flat over the slightly uneven deck joists.

The amount I'm talking about is approximately 1/8" in some areas.

I've attached pictures of the uneven joists, as well as overall pics of my deck layout.

Any comments are appreciated.


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Old 08-01-12, 10:51 PM
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I would consider shimming the low joists with some impervious material not prone to rotting, something on the order of cedar or even treated cedar. And obviously, trim down any high joists with judicious use of a skilsaw and coarse sander (being sure to treat the trimmed surfaces with wood preservative). Maybe those with more experience than I have in building decks will chime in shortly with better advice.
Old 08-02-12, 03:49 AM
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I would install my joist hangers first to make sure the outer edge is firm, then do as bridge says, shim up over the beam, under the joist to make them level. I would also use a string to ensure I was leveling them to the same point. You may have some high as well. Man, that's a lot of skewed hangers
Old 08-02-12, 06:06 AM
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I worked on an Ipe deck a few months back, and we made sure everything was perfectly straight. All the rim-joist connections were planed with a power planer to take off high spots. With a long straightedge you can identify which joists are high, and plane those down. Planing 1/8 off the high joist will make a huge difference in how much you need to shim on the "low" ones. Often, you won't need to shim at all. I would MUCH rather plane than shim, but sometimes a shim is needed. Get it as good as you can, but don't be surprised if the deck shrinks even more in the future, making the boards a little wavy again in some areas.

We used the Kreg deck jig and stainless pocket deck screws with the 5/16" spacing. Worked pretty well, but it makes your arm tired on a large deck.

If you want a cheap plane for this purpose (going over knots and the occasional staple is kind hard on the blades) the ones at Harbor Freight aren't half bad. (kind of like a disposable razor... lol)

If you leave your deck boards long and cut them last, you will find that the Ipe wants to tear out when you cut it on a 45. I found that you can rip in a 45 going one direction, but not the other, which was kind of odd. The Ipe would rather be cut at a 45 leaving a sharp point as you cut each piece, not the other way around. We also sealed all end cuts on the IPE with a brushable wax sealer. I'd recommend that.

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