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Decking fastened from below...???

Posted by tlcfargo (My Page) on
Mon, Jul 13, 09 at 22:45

I'm rebuilding an old, second-story deck, new everything. I've seen the hidden fastener systems which mate to grooves in the sides of the deck boards and clamp them down to the joists. Another approach I read about in Fine Homebuilding for elevated decks like mine is to simply go below the deck and toe-screw up through the joists, up into the decking (blind). You could probably even get away with coated (not stainless) fasteners.

I can see how this method might be slower for a time-conscious pro, but what might other negatives be?


Follow-Up Postings:

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RE: Decking fastened from below...???

I wouldn't go the toe screw route. Even if you pre-drill through the joist to keep from splitting it out, it is still a weak connect, imo.


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RE: Decking fastened from below...???

Thing is.... If you go the traditional route of topside hidden-fastener-clamped-edges, how do you service/replace deck planks located in the middle of the deck?

If you fasten from below, that task would appear to be much simpler.


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RE: Decking fastened from below...???

Good point! Guess it would be similar to hardwood, laminate, engineered flooring, or any tongue & groove project. You would have to carefully cut it out and face screw the replacement(s). If close enough to the edge of the deck, pull them all up to the point of the replacment pieces.

We're using eb-ty fasteners. Guess i would rip down the damaged plank, bisquit the new, slip it in there and face screw the opposing side.


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Another reason....

...why fastening from below isn't often done: If a deck is high enough to walk underneath and attach fasteners, the lower level is probably used as patio living space. Which might make the visible overhead fasteners objectionable (though #7 squaredrive screws would be hard to spot).

In my case, I want to at least keep the carport below mostly dry, so I'm attaching corrugated plastic to the bottom of the deck joists and draining the whole shebang off to the side, near the neighbor's property line. The drain collector will feed a tube that runs out through the ivy to the street.

I can probably save a couple hundred bucks or so on the fasteners, as I can't see the need for stainless steel over coated screws on the underside of the joists. Even if they eventually rust stain, you'd never see it.

Since times are tight, I'm also considering using regular #2 Douglas fir 2x6s for decking. I guess splintering could be an issue. But in a California desert climate with good exposure and ventilation, I don't see how mold or mildew could be the problem it is back East. But that's for another post....


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RE: Decking fastened from below...???

It is really hard to get the deck board to pull tight to the joist when fastening from below. Gravity is not in your favor.

You will need another person standing directly above you to compensate for the upward force. Or a couple of good clamps.

Your arm is going to be really sore as screwing up is not ergonomic at all.

It is really difficult to set screws at a consistent depth when towing in to the side of a joist. You run a chance of not getting proper embedment, or going all the way through and poking out.

This is so much unnecessary labor, I can't even begin. And the kicker- the deck won't last! Yup, that's right I said it won't last! The decking will twist, cup, and pull right up from the joists. I doubt you want to remove the corrugated sheets to service the deck after a year or two. Fastening down is the only right way to build a deck.

Every project I build with Doug Fir (usually PT .40 pcf/ACQ) I fasten the boards with stainless steel ring shank nails. The fastener lasts, it holds tight, and it doesn't corrode. Cost is very economical, installation is with a nail gun.


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Thanks, aiden...

...for the comments. If you don't mind, I have a few more questions.

Your Doug Fir ACQ projects -- are you talking about PT fir for the framing, or for the decking boards too? Don't know if I'd want to walk barefoot on an ACQ deck.

I've used the 0.113 SS nails/gun for Hardi siding. Cheaper than screws but almost as much work, since you have to predrill or you'll split the siding.

As for twisting, cupping and pulling, have you experienced any of that with the hidden fastener nail-clamps? Or do you just avoid that approach altogether?

I know what you mean about ergonomically challenging. But can it be any worse than hanging drywall on a ceiling? At least with decking I can use clamps, as you pointed out.


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RE: Decking fastened from below...???

I use the ACQ Fir for entire decks sometimes, everything but the railings. These are not a residential type deck, more of a light duty commercial application. The walking surface is painted with a non-skid paint and the handrails paint grade redwood.

I did one project fastening from below. The job was a Victorian in San Fran, and the stairs and landings were all paint grade. The owner wanted the screws hidden, so like an Idiot I agreed to use whatever idea they suggested. The product they wanted was a metal bracket system that did essentially toe screwing from below. The brackets were manufactured of insufficient gauge metal to remain in a rigid state as the screws were tightened (they were flimsy) and several of the screws ended up poking through while the boards were still sort of loose when walked on from above. Not to despair, I tried toe screwing through the joists with more screws (to heck with those stupid brackets). The problem is the clamp will only reach so far. The side where I can't get the jaws of the clamp, that screw pushes up away from the joist. I couldn't get it right and all this extra labor was a waste. I do not recommend fastening from below at all.


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Thanks again....

...aiden. Interesting.

Haven't seen a hidden fastening system that works from below. All the ones I've seen (including the new Simpson deck clips) work from above.

We've gone full circle on deck redesign here. Ipe, etc. are too expensive. The composites would match the Hardi siding, but are a little pricey too. Most (all?) of the horror stories I've read about mold buildup on composites seem to come from builders back East/South where you can just about wring the humidity out of the air. At the other end, one builder in (desert) Montana said he doesn't even bother with PT as it's so dry there. Here in SoCal we get less than half of Frisco's rain, and little fog.

A remodeler we know prefers apartment balcony-style cement decking (Life Deck): plywood, stapled lathe, acrylic-fortified cement, acrylic cement topping. Materials work out to around $3/sqft, but probably a little too industrial-looking for most homeowners. And on a larger deck, cracking from small quakes might become an issue. I think I'd like the deck to breathe a little more than that, too.

After reading your comments, I'm wondering how durable a painted decking surface could be -- with killer paint, you could use #2 fir and Bondo the rough spots. (I would think an oilbase paint would be necessary.) Or, just seal it every other year and call it "rustic."


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RE: Decking fastened from below...???

Shadoe track is a system that fastens from below. I used them on a project at the owners requaest, but wasn't real impressed.

Here is a link that might be useful: shadoe track


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