Do I need to replace my deck joists?

Submitted by RobotKevinSpacey t3_11czsxt in DIY

I'm about to start a project replacing my rotting deck boards, and I was hoping not to have to also replace the joists, so I pulled up a small section of the deck to assess them. Assuming all of the joists are in a similar condition to the few in the photo, do I need to replace them? I believe the deck was built in 2012. Photo

Edit: Thanks for the replies everyone. Sounds like all I need to do is give them a cleaning and install some joist tape and I'm good to go.

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wowsuchtroll t1_ja5xzhr wrote

If there is no rot, no need to replace. From what is shown they look clean.

If you are replacing decking with a composite it may be worth while to wrap the tops in vycor or similar while you have it stripped. This will depend on location, cost, long term plans.

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Mo_Jack t1_ja6rk3j wrote

My parents deck went 25-30 years before they had to replace their pressure-treated joists.

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cheezemeister_x t1_ja87l31 wrote

Same, but this really depends a lot on how close to the ground the deck is. My parents had a multi-level deck and the ground-level portion rotted after about 20 years. The upper level portion will probably last 100; the joints still look new @ 25 years.

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ImplicitEmpiricism t1_ja8zpcu wrote

Yeah, I have a ground level deck and after ten years two joists have minor rot. Okay for now but will probably need to replace in the 2030s.

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rjcarr t1_ja6y7pj wrote

Yup, I recently did this. Joists were about 20 years old and looked fine, but replaced with new pressure treated, added sealer, and put joist tape on top. Should last as long as the pvc deck boards, and sadly, me as well, ha.

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spiderborland t1_ja7q4gf wrote

Well today I learned about joist tape. After a quick googling, is it effectively the same as sheathing tape like Zip System? A rubber/rubberized tape that just lays on the top joist?

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inpantspro t1_ja7x15j wrote

Pretty much

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spiderborland t1_ja803rn wrote

Well cool. I came up with idea on my own at one point, but I assumed that it would trap moisture

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1HappyIsland t1_ja85i4d wrote

Reminds me of a friend shopping for a roof: 30 years! Do you have 10 year shingles? I'm so cheap I don't want to pay for stuff when I'm dead.

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dxrey65 t1_ja94df6 wrote

I still remember working at a car dealership when an older lady was at the counter paying for an oil change, and the salesman told her how she could buy a package that would cover her oil changes for the next five years. She just laughed and said "do I look like I've got five years left? Not likely!"

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Revolutionary_Eye887 t1_ja8stx5 wrote

I just did this too. Since I was installing Timbertech PVC I went ahead and replaced all my joists. 32 in all. Some looked like yours, some were much worse, but why install a long life deck board on lower life structure? I added sealer and joist tape to all the new joists.

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Spute2008 t1_ja7x681 wrote

Use that tape specifically made for this purpose

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velociraptorfarmer t1_ja88uo4 wrote

Did this at my grandpa's place before. We replaced everything except for the support posts and joists, and just flipped the face boards around the edge of the deck. 1/2 the work, and it all looked brand new when we were done.

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wmodes t1_ja93yvn wrote

Check extra carefully anywhere where soil might be in contact with the deck joists. If you replace them, replace them with treated two by sixes instead.

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Highlander2748 t1_ja5zx0j wrote

You can consider putting bituminous rubber strips on top before the decking goes on.

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drytoastbongos t1_ja6cfwm wrote

OP, look up "joist tape" for this. Super easy to apply and will definitely prolong the joists.

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Wellcraft19 t1_ja6hy5z wrote

Yup, joist tape should be mandatory to use on any deck project. Especially when using Trek, TimberTech, etc, as very few will ever inspect the joists after deck installation (as the boards last forever - which is not the case for joists that might be poorly protected, or worse, sitting directly in moist soil).

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DelayVectors t1_ja7v9gj wrote

Yep, bought a house with a raised deck, trex boards on top but they didn't even use pressure treated wood for the joists. It's about 10 years old and the top looks great, but I'm going to have to rip the whole thing out. Every other piece of wood besides the decking is mushy and disintegrating. It's infuriating.

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drytoastbongos t1_ja8gogl wrote

Realized my contractor installed my new TimberTech deck without joist tape, drives me bonkers. I'm currently debating whether I take the decking up to install or just roll with it.

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Wellcraft19 t1_ja8jfp3 wrote

Install now, and you might never have to deal with it. Leave be, and at some time you will have to replace the structure, while the ‘deck’ still looks great. Yet, that’s likely 20+ years out assuming all other boxes were checked.

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Tibbaryllis2 t1_ja873rd wrote

This is the first I’m learning of joist tape and I wanted to ask a question without hijacking OPs post:

Are there any situations where the joist tape isn’t indicated? I’m getting ready to replace the decking on a floating dock.

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Highlander2748 t1_ja88iru wrote

If you have a deck that may be covered by a roof, it may not be needed. It’s really only the last 15(?) years or so that’s it’s been more commonly used. The joist tape is used to protect the top face of the joist and employs a self sealing bituminous strip to seal around the fasteners and help keep the top of the joists from degrading too soon. It’s fairly cheap insurance, but it’s also worth noting that decks were built with pressure treated lumber for decades before this technology. I have never had a deck fail because I didn’t use it.

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Tibbaryllis2 t1_ja8l68e wrote

Thanks for the reply. The dock decking is mostly covered by a tin roof, but the dock perimeter and ~40 feet of catwalk from the shore is not.

The house was built in the 50s and this will be only the third time we replace the decking, but I’m not shy about incorporating new best practices.

The way the decking is built, the joists (?) underneath are laid horizontally (2x6s, 6 side up) for attaching the deck to, so there is quite a bit of lateral surface to collect water. So we do have some issues with it rotting out where we screw in the decking. While the exposed decking suffers the most from 24/7 full sun (house on the north side of the lake so the decking is south facing).

Edit: I think we’re also victims of the pressure treatment regulations change as we replaced the decking only ~15 years ago and it’s already pretty soft in some places compared to the original decking in a pile on the property still having some pretty sound pieces still.

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Highlander2748 t1_ja9bp9q wrote

Your description of the framing off the dock is concerning because I can’t think of a reason where joists would work as intended when installed as you describe. Their strength comes from being installed with the narrow edge used to support the decking/floor. You’re correct about updated pressure treated wood regulations. The ACQ lumber does not seem to be as hardy as the older CCA lumber. You may want to see if any dock builders supply a different grade of PT lumber? You could also use Mahogany/Ipe/Teak or any number of more exotic lumbers that stand the test of time better. I also suspect the decking failure may be connected to the joist positioning as that is a lot of surface area to have moisture trapped and it’s just as capable of damaging the underside of the decking as it is the top face of the joists. In your instance, the application of the joist tape may actually trap more moisture and hold it on the underside of the boards.

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Tibbaryllis2 t1_ja9q0sx wrote

Oh sorry for being misleading. It’s a welded steel frame with 2x6s laid over them to give area to screw to when laying the decking. All the decking ends overlap steel crossbars and tie into the underlying 2x6. (Edit- I assume it’s a standard way of building them because all of the neighbor docks are the same).

So it’s structurally sound, but the boards underneath are the first to rot (due to the lateral surface area available to hold moisture). Followed by the decking board ends where they’re in contact with the underlying wood.

Re: your last statement, that’s what I was curious about too.

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itman404 t1_ja7p5cp wrote

> Yup, joist tape should be mandatory to use on any deck project. Especially when using Trek, TimberTe h, etc, as very few will ever inspect the joists after deck installation (as the boards last forever - not the case for joists that might be poorly protected, or worse, sitting directly in moist soil).

yeah, joist looks good, if he put tape, should last another 10-20 years.

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Bobmanbob1 t1_ja5yse5 wrote

Pressure treated Pine. They will be fine. If you have them totally bare, you can slap a sealant on them if you want.

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loptopandbingo t1_ja7bneg wrote

Not necessarily. Depending on when the deck was installed and where the wood came from and what it was treated with, there's a possibility the pressure treatment was ineffective. There's a class-action lawsuit going on about it. OP is probably fine, but at work I'm currently dealing with the bad wood that's totally rotten on the inside from the years of terrible batches of PTL.

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Wildcatb t1_ja7qbjn wrote

I was building my house when the new and 'improved' treatment standards were imposed. Half the treated lumber I used was old, good, long lasting treated pine. Half ended up being the new crap. I've replaced most of the new stuff at least once since then. To say I'm displeased would be an understatement.

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ekjustice t1_ja65bl5 wrote

Try to poke 1/4 inch flat screwdrive into the beams where the gap in the deckboards was. If it doesn't sink in more than 1/4 inch you are good. I second the "wrap the tops" suggestion.

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Craftsm4n t1_ja68t0v wrote

When they are dry and above freezing temps for 48 hours!!!

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razeronion t1_ja5y7la wrote

They look like pressure treated lumber so they should be fine. I'd give them a coat of sealer to help preserve them anyway.

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redonkulousness t1_ja649n1 wrote

I’m doing my entire deck right now. I’m applying deck tape to the joists just to give them a little more weather resistance. It’s cheap, effective, and easy to do.

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AKAMH t1_ja6fplv wrote

Something to consider, are you replacing the decking with the same material? If not, check the recommended spacing for the decking especially if you are going with composite/trex. Some wood decks were built with up to 24” span between joists, more commonly 16”, but some composite decking is more flexible and requires 12” spacing.

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Soklam t1_ja7m76m wrote

I think most composite decking is 12" on center spacing. Good point for sure. Trex will start to look like it's melting if it's on 16" centers.

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ultralightlife t1_ja7rlrs wrote

trex recommends 16" and decking companies around here never do 12" unless specifically requested.

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serotoninOD t1_ja803gq wrote

16" is fine if you're just laying it out straight. 12" spacing is recommended if you're doing diagonal decking at 45°.

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Klaatu162 t1_ja7lkn6 wrote

**Most deck failures are due to rotting of the rim joist attached to the house or improper nailing or rusting of the joist hangers and nails. While the deck's structure is open after removal of the decking, please inspect all structual elements for good condition. All decks should be inspected every 10 years at a mlnimun. If the deck is attached to the house, make sure the attached rim joist is not just nailed to the house, but thru bolted to the house's rim joist and flashed properly. If you have the deck rim joist attached to a brick wall, again, make sure the rim joist is thru bolted to the house rim joist.

The joists themselves look fine. And yes, I would clean them off and use deck tape or a butyl rubber sealant tape on top of them.

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Reggie5633 t1_ja9prvr wrote

100% this answer. I was hoping to do what OP is describing last summer, but ended up replacing nearly all the framing too. While the joists seemed OK, behind the ledger board attached to the house was NOT. Carpenter ants had eaten into part of the plywood sheathing and I’m so glad I caught it.

OP - do yourself a favor and check behind the ledger board before you start planking over the joists. You’ll at least have a chance to add flashing tape if there isn’t any already.

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insightsometime t1_jaaa7d8 wrote

The ledger board and its attachment to the house structure is where you will find the rot. You may be able to save the joists even if you have to replace and flash the ledger board.

Do not take the advice of strangers on Reddit who don’t have a sense of the attachment to the house. Get an opinion from a seasoned builder who can inspect the integrity of the ledger board.

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Klaatu162 t1_jabgy9u wrote

Yes, I agree. Get a seasoned deck builder, architect, structural engineer, or a local building inspector to evaluate your entire deck while everything is exposed.

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victorgrigas t1_ja6539s wrote

No, but look for spots with rot

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Senior_Cheesecake155 t1_ja6b2wy wrote

The ends of the boards will tell a lot as well. But from this picture they look ok.

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zugg414zugg t1_ja6by5a wrote

Look decent, but please do yourself a favor and get some joist tape as others have mentioned.

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Trail-Commander2 t1_ja62bwg wrote

It’s almost always the boards and not the joists that need replacing.

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SuspiciousChicken t1_ja69emu wrote

Those look just fine. No problem - plenty of life left in 'em. Plus, if they fail, it isn't like you are falling 2 stories.

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Strive-- t1_ja7afqg wrote

From what I see, no, you don't. The boards may be discolored but unless there are areas where the board it rotting, you'll be okay.

Be mindful of where the wood makes contact with the ground - water is the killer here.

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RedditVince t1_ja7jt3u wrote

Yeah based on this picture they look OK. Be extra careful of corners and edges.

My House on my deck, even if the boards are all perfect, I would pressure wash, let dry and then recoat with wood treatment. With a good fresh coat they will last even longer, make sure to replace anything that is even a little soft.

I have never used Joist tape(?) so I am not familiar with the product. I would guess it covered the top few inches of the board and that will probably help in the long term as long as the boards can dry out properly.

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big_bertnor t1_ja9rrfr wrote

I always use the copper wood treatment on joist tops too. Easy brush on, thank God the smell goes away relatively quickly because I can not stand that odor.

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groceryburger t1_ja6e3z1 wrote

You’re good. They’re just stained.

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Consistent-Net1653 t1_ja6gv7e wrote

It’s also a good idea to remove any debris or dirt that’s settled in creating ground contact with your joists.

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bmor62 t1_ja6v2wm wrote

They look good. No need.

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HairyTales t1_ja75qaw wrote

Looks just wet and dirty. No need to worry unless you see actual rot or signs of an infestation.

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babygrapes-oo t1_ja7h0fk wrote

Those joists look good and like Pt, so go add some top decking and go enjoy a lay with the wife

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DistantOrganism t1_ja7t47v wrote

The joists are ok. Everyone is talking about joist tape but you must evaluate the fasteners holding it all together too. It’s not uncommon to find the screws are severely rusted and about ready to snap.

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JasonDJ t1_ja8end3 wrote

Fasteners? Hah, whoever built my deck just toenailed all the joists to the ledger.

Damn deck fell out the first party we had. Fortunately it still stayed "up", just shifted a bit. Also it was only like 3ft above ground.

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Warlord68 t1_ja64pj0 wrote

You can protect the top of the joists with water proof material going forward.

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SURGICALNURSE01 t1_ja683vw wrote

This last year I took up all of the deck boards and planed them down to looking like new. The previous sealant I used was terrible. The boards all looked dirty and dark brown. The joists looked very good and the deck ended up looking like new

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OmiSC t1_ja6oy4h wrote

Looks fine to me. I wouldn't replace them.

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Bernadette__ t1_ja6pzab wrote

As others have said, no need to replace if they are all in good shape.

You don’t mention if you are replacing with composite or wood, but if the plan is to use composite and the existing joists are 16” OC, then you will want to consider adding additional joists to better support the composite boards.

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dial-up_ninja t1_ja6x8bo wrote

I'm also following the SteamDeck sub and this popped up on my feed and I thought its a pretty weird picture for changing the joysticks of the deck.

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itchyfrog t1_ja767cx wrote

If they're not rotten they'll be fine, you can always give them a slap of anti rot stuff to be sure, especially on the ends.

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the_one_username t1_ja79y0o wrote

Power washing and adding deck tape would be good. Tape at least. The wash would make it look clean

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Middle_Assignment956 t1_ja7dkfu wrote

The picture looks good. Test them by driving a nail into one of them. If the mail goes in as you would expect, they’ll be fine. If it feels soft or spongy, they will need replaced. I used some tar paper on mine to cover the top and folded it over about 50% of the sides to keep water off the joists. The joist tape works fine but it’s very expensive if you have a large deck and only protects the top.

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Oppyeahuknowmi t1_ja7etv9 wrote

They look good. if they're warped or a little wonky you can always sister on some 2x6

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Zandt88 t1_ja7fkqs wrote

There's a bit of surface staining but I see no rot.

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cuzisaidit t1_ja7n2dy wrote

When you take off those boards, just check for a break. More than likely there is 1 or 2 snapped, most likely at a bad knot.

If using composite, double check the installation instructions. We recently did one that called for the joists to be 12" on center, the composite boards have more flex requiring more support as to not sag.

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VagueGooseberry t1_ja7w7ms wrote

You’re good. I had some that had rotted when we redid our deck when after we moved in and those we replaced. Put some joist tape if you’re exposing all the joists when you’re removing the boards.

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johnnycyberpunk t1_ja7y3rj wrote

Had the same situation with my deck about 2 years ago.
Pulled all the decking off and pressure washed the joists - they were in great shape except for the ends that were in hangers connected to the ledger. Pressure washer blew through the rot and I could see I needed to replace them all.
Sucked that it was just the last 1-2" of board that ruined it.

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MrCuckyMcCuckFace t1_ja8326g wrote

Look good to me. I just redid my 20 year old deck and your joists look cleaner than what I had. I did block them to add stability and now you could land a helicopter on the thing. Definitely consider blocking it. It’s an amazing and cheap huge difference maker

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Topher_86 t1_ja86do9 wrote

Wood looks OK

One thing I can’t see from this photo is the ledger board. Take a good look post demo to make sure it was properly installed. While unlikely, it’s not necessarily uncommon for people to cut corners on deck installs.

Ledger board should be secured using staggered lag bolts in two rows. Various code depictions can be found online. What can sometimes happen is installers won’t stagger the bolts either correctly, or at all.

Beside this take a look at the hangers and make sure everything is abutting correctly and not pulled away from the ledger. Another common oversight is installers won’t fully attach hangers. Again, code depictions are online.

All of these build issues should be inspected/corrected now before you spend time or money on new decking.

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wracompton432 t1_ja8w6c5 wrote

Hit it with a hammer in a few spots if you put a hole in it shes soft replace if you dent it send it

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atkinson62 t1_ja9euq7 wrote

lol those deck boards may have lasted bit longer with some care and some separation for water drain.

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desitelugu t1_ja9hl5c wrote

this deck looks exactly like mine I am struggling with a loose deck from past 3 months how did you remove the deck ?

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ITeachAll t1_ja9kw9u wrote

Slap some good joist tape on and you’re good to go

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coopertucker t1_ja9siod wrote

From my view, they look good. They are green treated and off the ground, they look good.

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SoraUsagi t1_jaa5pky wrote

Mine looked like this. And I didn't. I did, however, run black weather stripping/tape along the top to try and prevent water from collecting in the old screw holes. I went from lumber to composite. Was... Fun.

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DeeEmm t1_jaaqyrr wrote

If they don’t spark joist then they need to go.

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Chupoons t1_ja6iuxv wrote

Give it another 5 years.

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coupdevill t1_ja809yl wrote

First thing you need to do is get those joists off grade, six or more inches clearance would be ideal, so air can move through there and stop the rot. Then replace rotted out joist.

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roopjm81 t1_ja84hwc wrote

I was going to replace mine with composite, on demo day we pulled up some of the old boards and chunks of the joists came with. The deck was 5 years old. Guess the guy who built it didn't use treated wood.

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todd149084 t1_ja89uwk wrote

If you’re going to spend a lot of money on composite decking and want it to last I would replace all the joists with pressure treated lumber rated for ground contact. When I redid my deck this summer (after about 7 years) the very few houses I used that were not PT had rotted away.

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macetheface t1_ja8nou9 wrote

If they're not sitting on the ground, which it looks like they're not - good airflow and no insect damage then most likely fine.

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sfzombie13 t1_ja910ol wrote

they look good to me, but i'd beat on them to see if the wood is soft. if it is it needs replaced, but you may be able to just scab a 2x4 on the side near the top.

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ASDFzxcvTaken t1_ja94wiv wrote

Looks fine in the pic you took but the place you really want to check is at the end of the joist. Thats where they absorb water the most and rot and fail. That's also usually where it attaches to the wall or whatever is holding it in place. From my personal homeowner experience with several decks, if the ends are good the rest is probably good.

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whatinthenameofholyf t1_ja95aa7 wrote

The current boards look like they're butted right up against one another. I could be wrong but I think you want a gap ~5mm gap between each. Should help the water drain away and improve air circulation underneath

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wessex464 t1_ja9r0ze wrote

I just poke at it with a screw driver to find rot, you can easily tell because rot just crumbles/falls apart. I just did this last year with my deck and I had to sister some boards in places where I found a bit of rot at the surface that would affect the deck boards sitting flat but not impacting the strength of the joist itself.

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PaleFlyer t1_jaag0ab wrote

"joist tape".

That moment where you have to Google to see if you are being trolled by another "yard of flight line" or "blinker fluid", or "left handed smoke shifter"...

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beeezyboy t1_jaao9l7 wrote

Take a screwdriver or pocket knife and stab the joist. If the wood is soft and rotten change them out. From the image, they don't look bad. But I always do a stab check to be sure.

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KRed75 t1_ja623by wrote

We live in a sad time when a pressure treated deck doesn't even last 10 years. I built mine 15 years ago and after about 10 years, the deck boards were rotting badly. Pulled some off the the treated joists are also rotting in several places even though they are ground contact rated and are 2-3 feet above the ground level.

Now I need to decide if I pull the desk out completely and just build small platforms and a few steps for the 3 french doors and plant grass or if I do pavers or stone.

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beau_loop t1_ja6prqd wrote

Yeap, totally, those are loads bearing struts, you will want to whitewash them in a sealant and compress the air out of them for a firm texture.

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