Best way to lay deck boards on exposed trusses?

I’d definitely add some blocking or at least sleepers on top of those trusses - attaching deck boards straight to open web steel is asking for flex and squeaks, not to mention weird gaps. I learned the hard way that skipping this step makes everything feel bouncy. For airflow, just keep normal spacing between deck boards and you’ll be fine outdoors. Don’t try to bridge big gaps with decking alone... it won’t end well.

I get where you’re coming from, but I’ve actually seen some folks try to use composite decking right on steel trusses, thinking the material would be stiff enough. It really wasn’t - lots of bounce and weird noises, just like you said. Curious if anyone’s tried using rubber or foam strips between the sleepers and steel to cut down on vibration? I’ve wondered if that’d help with the squeaks or just make things worse over time...

- Seen a few jobs where folks tried foam strips between steel and wood - mixed results.
- Helps a bit with vibration, but over time, the foam can compress or even break down, especially if there’s moisture.
- Sometimes it actually made the squeaks worse as the foam aged and shifted.
- I usually go with treated wood sleepers, fastened tight to the steel, then deck boards on top.
- Anyone ever tried those rubber isolation pads they use under machinery? Wonder if that’d hold up better than foam in outdoor conditions...

Rubber pads under sleepers sound good in theory, but I’ve seen them trap water and speed up rot if you’re not careful with drainage. Steel trusses flex more than wood, so direct attachment usually leads to noise or loose boards over time. Blocking between truss chords helps a lot - just takes extra time. I’d skip foam, personally… never seen it last outdoors. If you go with sleepers, make sure they’re pressure-treated and spaced tight enough to support the decking - don’t trust the truss spacing alone. Learned that one the hard way on a rooftop deck job last year.

- Good call on the rubber pads - seen the same issue with water pooling, especially if the slope isn’t perfect.
- Steel trusses definitely flex more than folks expect. Blocking between chords is a pain but really does help with stability and noise.
- Pressure-treated sleepers are a must. I’ve had to replace untreated ones after just a couple seasons... not worth the risk.
- Agree on foam - never seen it hold up outside, especially with freeze/thaw cycles.
- Decking over steel always takes more planning than people think, but sounds like you’re covering all the right bases.

Yeah, pressure-treated sleepers are non-negotiable for me too - anything else just rots out, especially if you’re dealing with any kind of moisture. I’d add: if you’re looking for longevity and want to keep things green, consider composite boards or even recycled plastic lumber. They’re pricier up front but way less maintenance and don’t feed mold or insects. One thing I’ve learned the hard way: don’t skimp on the membrane between steel and wood. Galvanic corrosion sneaks up faster than you’d think...

One thing I’ve learned the hard way: don’t skimp on the membrane between steel and wood. Galvanic corrosion sneaks up faster than you’d think...

That’s a good point about the membrane. I skipped it once to save a few bucks and ended up with rust stains and soft spots after just a couple years. Anyone tried using regular landscape fabric for that, or is it not tough enough? I’m always looking for ways to cut costs without cutting corners, but sometimes it bites me.

I’ve actually tried landscape fabric as a barrier, thinking it’d be a cheap fix, but honestly, it didn’t hold up well. After a couple of freeze-thaw cycles, it started to break down and let moisture through. The steel ended up with some rust, and the wood got a bit spongy in spots. If you’re set on saving money, maybe look at ice & water shield or even heavy-duty roofing felt - those seem to last a lot longer. Sometimes cutting corners just means redoing the job sooner than you’d like... learned that the hard way.

Yeah, I’ve seen landscape fabric fail more times than I can count. It just doesn’t cut it for moisture protection long-term, especially with freeze-thaw. Ice & water shield is pricier up front, but I’ve never had to go back and fix a job where we used it. Roofing felt’s decent too, but it can tear if you’re not careful during install. Honestly, sometimes cheaping out ends up costing more in the long run... learned that lesson myself after a couple callbacks.

Honestly, sometimes cheaping out ends up costing more in the long run... learned that lesson myself after a couple callbacks.

That really resonates. I tried using landscape fabric under a small shed deck once, thinking it’d save some cash, but it just didn’t hold up after a couple winters. The freeze-thaw cycle up here seems to chew through anything that isn’t heavy-duty. Have you noticed if ice & water shield ever gets brittle over time? I’ve read mixed things about longevity when it’s exposed to temperature swings.

Also, when you’re laying deck boards on exposed trusses, do you find that the extra thickness of ice & water shield throws off your board height at all? I’ve been worried about creating an uneven surface or trapping moisture between layers. I’m leaning toward using felt for my next project just because it’s thinner, but your point about tearing during install is spot on - especially if you’re working solo and the wind picks up.

It’s always a balancing act between cost, durability, and how much hassle you want to deal with down the road. Good to hear real-world feedback on what actually works long-term.

Ice & water shield definitely gets a bit cranky after a few years, especially if it’s seeing sun or wild temp swings. I’ve peeled up some that felt like old duct tape - cracked and sticky in all the wrong ways. As for the thickness, yeah, it can mess with your board height if you’re not careful. I ended up using felt once just to avoid that “wavy deck” look, but then a rogue gust turned install into a slapstick comedy routine. There’s really no perfect answer... just whichever headache you want to deal with less.

I get the frustration with ice & water shield, but honestly, I’ve had better luck with it than felt in my climate (humid summers, freezing winters). The trick for me was using the thinner stuff - less “wavy deck” and it didn’t mess with my board height as much. Felt just never held up for me, especially after a couple seasons of rain and sun. Maybe it’s just the brands I tried, but I’d rather deal with sticky than soggy any day.

Sticky beats soggy, for sure. I’ve had similar issues with felt - especially on decks that get hammered by sun and then freeze solid in winter. The stuff just curls up or gets brittle, and then you’re chasing leaks every spring. I tried the “economy” felt once and regretted it after the first storm.

The thinner ice & water shield is a good call. I used the heavy stuff once and it was like wrestling a giant fruit roll-up... plus, it made my deck boards sit weirdly high over the trusses. Thinner membrane seemed to lay flatter and didn’t mess with the board spacing as much.

One thing I learned (the hard way) is to keep a stash of mineral spirits handy for cleanup - otherwise, you’ll be peeling sticky bits off your tools for weeks. Not ideal, but still better than dealing with mushy felt after a wet season. If you’ve got exposed trusses, that extra bit of waterproofing really does help keep things solid over time.

That’s been my experience too - felt just doesn’t hold up when you get those wild swings between hot summers and freezing winters. I tried to save a few bucks with the cheaper stuff once, thinking “how bad could it be?”... Well, after one season, I was patching leaks and cursing myself every time it rained. Lesson learned.

I’m with you on the thinner ice & water shield. The thick stuff is a nightmare to handle, especially solo. I remember trying to lay it out and it kept sticking to itself, then I’d have to peel it apart and it’d stretch all weird. Plus, it made my deck boards sit uneven, which drove me nuts every time I walked across it.

One thing I’d add - if you’re on a tight budget, sometimes you can get away with just taping the seams of the thinner membrane instead of covering the whole surface. Not perfect, but it’s helped me avoid the worst of the leaks without breaking the bank. And yeah, mineral spirits are a must... I’ve ruined more than one pair of gloves forgetting that step.

- Totally agree on the felt - just doesn’t cut it with big temp swings. Seen too many decks rot out faster than folks expect.
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“the thick stuff is a nightmare to handle, especially solo”

Man, you nailed it about the thick membrane - tried to wrestle that stuff onto a shed roof last fall and nearly ended up wrapped like a burrito. And yeah, felt just doesn’t stand a chance out here with these wild temp swings. I’ve seen more than a few decks get soft spots way sooner than expected. Good call on checking for dips before laying boards... nothing like discovering a puddle right where your grill’s supposed to go. Appreciate the real-world tips, especially the one about mineral spirits - those gloves are basically single-use at that point.

Good call on checking for dips before laying boards... nothing like discovering a puddle right where your grill’s supposed to go.

That’s the step I always end up regretting if I rush it. I’ll usually run a long straightedge across the trusses, then shim any low spots before putting down the first board. Makes a huge difference in drainage and how solid everything feels underfoot. Curious - has anyone tried using self-leveling compound on outdoor decks? I’ve only used it indoors, but sometimes those dips are just too much for shims alone. Wondering if that’d hold up in freeze/thaw cycles or just crack apart.

Tried self-leveling compound once on a deck in Minnesota - big mistake. Looked great for a season, then winter hit and it started cracking like crazy. Those freeze/thaw cycles are brutal. Shims or sistering a new joist seem to hold up better long-term, at least in my experience.

Self-leveling compounds just don’t stand a chance up here - totally agree. I’ve seen them fail on decks and even some interior spots near exterior walls. For exposed trusses, I usually recommend shimming or sistering like you mentioned. It takes more time upfront, but you get way fewer headaches down the road. If the joists are really out of whack, sometimes it’s worth pulling a few boards and doing a full sister rather than trying to patch things up. The freeze/thaw cycles just find every weak spot...