Liquid Nails vs Loctite PL Construction Adhesive - Which is better? Pull off testing!
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- เผยแพร่เมื่อ 28 ส.ค. 2024
- Big Thanks to Lowes For Sponsoring This Video! We are testing Construction Adhesives found on the shelf at Lowes. $3 glues all the way to $8 glue. Locktite vs PL in a pull off test. The results are along the lines of what you would expect yet there were still some surprises. A more expensive glue does yield a higher PSI pull off test.
Go follow Jordan’s TH-cam channel here: / @jordansmithbuilds
Jordan’s follow up test video with Loctite PL Max - • Video
Matt’s Instagram www.instagram....
Jordan’s Instagram www.instagram....
I make a mistake guys: I read the scale in Pounds but it was set in KiloGrams! Yikes. Sorry! The test still holds but the numbers I’m stating are wrong. The multiple is 1Kg = 2.205 Lbs. I was off by a factor of 2.
Dude, that is a HUGE factor to be off. Don't be so quick to sellout for that $$, maintain editorial control.
Just put in those little caption squares on the edit. Honest mistake, people.
christschool pounds to kilograms is a big difference but makes zero difference when comparing adhesives to each other using the same scale. The results are relative to each other. The first test was the baseline. Could be reported simply as 1 since this really isn’t a real world application per se. and the subsequent results as say 1.5x, 3x, and 5.3x the strength. What we do need is at least 3 samples of each test to start to see the variation and account for that in the results. Now, if he were to take this setup and design a load supported member using this information... he was have a 2.205 factor of safety built in lol.
@@TherealEggiejr I agree, its an honest mistake. However, he's trading his trust for Lowe's money. Long term, not good for him. 287k subscribers is really tiny, compared to similar channels that didn't succumb to corporate America. Doubtful Lowe's will like this mistake and will ask him to remove it.
@@SigmaDG "christschool pounds to kilograms is a big difference but makes zero difference when comparing adhesives to each other using the same scale". Yeah, right. The bigger issue is this video really hurts his brand.
LT Ext HD - 44.2 kg - 97.44 lb
LT Fuze It - 121.6 kg - 268.08 lb
LT PL Pro - 275.0 kg - 606.27 lb
LT PL FG- 367.0 kg - 809.09 lb
We have used the PL premium 3x for years now and I have never had a failure. We glue down our green plate in high traffic areas when we finish basements and one time we accidentally glued the door cut out down. When I went to remove it I also removed a inch deep channel of concrete where the glued was gunned out. It was then I knew we were using a great product.
Happy New year!
C&J Remodeling
Oops... I’ve done that.
Yikes!
I would never use any other product other than PL
I recommend screwing down plates with tapcons. No need to mess with glue, and you can pull em out easy if you need to move the wall. F those loud concrete nailers that never once set a nail all the way ever in the history of building
Kevin R actually our ramset works great and tap cons are very slow. Hearing and eye protection always on so no extra hassle for loud noise Also tap cons break. Power nailer works great and glue is cheap insurance.
I really like this series of head to head real world testing of products. It is exactly what every builder or consumer wants. I hope you keep it a regular addition to the channel. Dedicate a day to uploading experiments... Head to head saturdays, test rig tuesdays, mainly experimental mondays, etc
Matt, I won’t insult your other excellent content by saying this is the “best video you have ever done” but I want to encourage you to continue to make these kinds of product test/comparison videos, I find them interesting and informative, and just really *fun* to watch. You have such great energy and enthusiasm and I enjoy it.
Having said that, kudos for taking the time to think about possible issues like being careful to follow manufacturers directions to mist with water, etc, but there are several shortcomings you might consider:
1) run several (at least 3, 5 would be better) tests of each product. Either the results will be consistent, in which case you can feel confident, or they will vary a lot in which case you know to look for variables you missed.
2) pay attention to details like is your scale displaying KG or LBS, or if you are *really* testing shear or a combination of shear and tensile strength or something else. None of these issues necessarily invalidate your results but certainly do cloud them. The exact same video edited to say “KG” instead of “LB” and “we will be testing loads similar to what would be found in the real world when you glue a board to a wall” instead of “shear strength” and presto, 90% of the negative comments go away and your conclusions are much stronger.
3) I would love to see some tests done in extreme cold or hot conditions. I’ve seen brittle failure of construction adhesive in sub-freezing temps and would be very interested to know if that varies between different products. (I have a summer cottage in the mountains, years ago I had put some art up on the walls with a removable adhesive strip designed for that kind of temporary light-duty work, and when I came to open up the following spring all the art had fallen off the walls, apparently the adhesive stopped working in the cold winter months.)
Have a very Happy and Successful New Year, and keep the good content coming!
I totally agree, I hope that he gets better with the depth of his tests, this is exactly the content I want to see. Different moisture levels would also be cool to see, in addition to different temperatures. I enjoy project farms testing videos, too.
I use PL Premium 3X exclusively for wood to wood joinery and it has never disappointed. Some if not most of the Liquid Nails adhesives I'm finding are "GreenGuard" which means they're water-based and not near as good as chemical based. PL Premium is polyurethane based adhesive and is, in my opinion, a superior product.
AWESOME video. Loved it. I’m floored at the strength comparison between the different adhesives, I would have never imagined such a wide breadth.
Impressive results for all. I was surprised how much of a difference there was from the cheap to the most expensive.
Your winch scale was in KG not lbs
Yeah kg not lbs hey
Math sucks too
Love that you’re with Lowe’s!!!!
This is so cool! Thank you for a great and helpful video. This increases my already high respect for Lowes.
Been using PL Premium for many years. Love the stuff.
Correction, Jordan: yours is not a SHEAR test. It is a test of TENSIL strength - resistance to being pulled apart. Shear testing involves SLIDING the two surfaces apart. Example: slap some adhesive on a brick; stick it on a vertical surface and if it sticks, after it cures measure the vertical force to the point of failure. Doesn't have to be vertical, it can also be horizontal or anything in between.
It would be nice to see a test of longevity of the joint and their ability to perform over moisture/temp ranges which is often as important as overall strength. That would require access to HALT and/or HASS chambers.
They could rig up their own, they'd have to have a hole in the top for the chain. Maybe some tubular steel to make a sliding seal
Thank you Matt & Jordan, these are real world tests that give us some insight when choosing products off of the shelf. Keep it up.
PL 3x is easy to work with, it performs great, and is very forgiving. PL 8x is super difficult to work with and very frustrating to get the conditions right so you can take advantage of its strength. There's a lot more to an adhesive than just strength... So for people rushing out to get 8x, don't. Use 3x instead. I've always had the wood and concrete fail before 3x anyways. I've never had the need to glue metal to anything, but if you do, I hope it's not something structural where you're relying solely on the bonding strength of a construction adhesive...
PL 3x is very durable stuff to be sure. 😊🌎✨
Another great video Matt & Jordan 😎 As some replies state the scale appeeeears to be set in Kg which means the adhesives performed much better than it seems as u will MULTIPLY Kg x 2.2 to find the value in Lbs. ...sooo the 362 is: 796 lbs !! 😯 Shoooo DOGGIE!! 🙃
I learned about PL from some guys while working construction. I've tested it before by gluing 2x4s together and then banging them apart with a hammer. One of the pierces of lumber would just rip in half before the glue joints ever failed. PL is the shit.
That’s not shear testing. If you insist in using this type of methodology, then drill a hole in the top of the block and pull from there. That would be shear testing.
Your present testing, appears to show the snap hook pulling off to the side causing failure in one side of the blocks.
I’ve performed thousands of double lap shear tests.
Would putting wood on the sides of the blocks to hold them in place work with his current setup?
@@sugarbooty+
The problem with the testing methodology is that as the load is applied, the snap hook pulls off to one side, causing an asymmetric/off axis loading of the wood that's bonded to each side.
It would have been easier to have one piece of steel shaped like T for the bottom fixture, then a straight piece of steel with a hole on one end, with the wood blocks spanning the 2 pieces of steel.
The set up I described would test the glue line bond between the wood and steel, which is what he's attempting to do.
@@gungadinn There are two adhered surfaces which means it now matters where the center is. This creates a slight torque if the hook isn't centered. Further the wood can stretch and the wood isn't the test material. On the other hand it may be that neither of those factors are significant. The adhesive is elastic, wood might resist stretching well and the torque may be so small that it barely has an impact. BUT they are all uncontrolled unknowns.
Yep, a bolted type connection on the top block would be ideal. This would keep the tensile load centered and consistent on each test. I also do tons of pull testing on our threaded products and the last thing you want is the specimens to shift as you apply a load or apply a load off center. Introduces bending and possible torque unknowns as mentioned.
I've used liquid nails and never been too impressed, but it does the job. I've used PL 3x and 8x, and i prefer 3x. May not be as strong as the 8x but it's easier to work with, and believe me, the 3x is very very strong. You'll have to destroy your work piece to pull apart after 24 hours. its insane how strong it is.
So great that I was just needing to purchase glue for a project, keep up the great work matt
I used PL 375 construction adhesive (the solvent-based stuff!) and twist-shank nails to assemble my tool shed with. That thing is SOLID! A large branch fell on it last year in an ice storm; didn't even faze it.
I've used PL8x for many years in my jobs, and sometimes it's TOO good. If there's any chance you need to take certain materials apart to access something, well, in my experience you mostly can't. I recall gluing some decorative landscaping wall blocks together for a client and she decided she didn't like it where it was and asked me to re-assemble it somewhere else in her yard, and I couldn't separate the blocks with a hammer and pry bar!. The blocks instead cracked. That said, I wouldn't use anything else for applications where the bond is vital. P.S. I've noticed in the last year Lowes stopped stocking it and replaced it with Loctite's clear 'PL Ultimate', at $3 more, tried it and TBH, I liked the way the 8X performed MUCH better...I thought maybe Loctite discontinued 8X but I hope that's not true..
Great video Matt, loved it. Been using PL for awhile. Needed to pull two 2x6s apart after gluing, didn't happen. Please don't get this on your fingers as I learned, it has to wear off.
What about wood to wood, best subfloor adhesive?
We use Leech F-26 for installing slate and marble fireplace surrounds , stone hearthstones, and sometimes glueing barn beam mantels on a shelf. I also hate when a customer changes their minds or something gets damaged and I have to remove something. Not easy to remove. It's much better than the standard liquid nails for sure.
The "ultimate takeaway" is they're all well beyond good enough for almost every construction task.
William Guenthner The only issue is none have elastomers in them. So while houses move back and fourth during weather conditions this stuff cracks and separates.
Unlike rare construction adhesives that are elastic like and allow for movement without the adhesive separating...
just what I need. i am doing a custom camper and unfortunately can not nail into the siding, so I will need to use construction adhesive to glue the frame and stuff to add sinks and stuff and drawers.
Another really good test for these type of products that I think people would like to see would be to glue a 2 x 4 to a piece of plywood and then set up a jig with the plywood waited down with say 2000lbs on it or something and then use your chain hoist and a bolt through the 2 x 4 to try to tear the 2 x 4 off of the plywood...
Also try pressing the 2 x 4 from the side to see when it shears off.
I would say one of the most common applications for this type of glue is the gluing down sub floor so I believe that would be of interest to people.
i used the PL 3X on the Advantech tongue and groove joints. it suggested a polyurethane adhesive and that’s what i used. 👍🏻
I'm still a fan of liquid nails for some applications. PL is a PAIN to dispense if you don't have an electrical caulk gun or if the tubs aren't warm. Most uses for liquid nails are also attached with nails and if your doing a few thousand square feet of subfloor it is nice to be able to get the material out of the tub and and attached before your glue has "skinned". getting up to 40 plus feet of adhesive in about 5 minutes can be really tough on the forearms Them repeat annother 50 times for the rest of the day.
For glue tests, I would suggest viewers go to Matthias Wandel's channel. He's not schilling for anyone. Its one reason he has so many subscribers.
CHECKED OUT HIS CHANNEL BUT DID NOT FIND GLUE TESTS. BUT WAS INTERESTING AND NOT COMMON. HE TESTED A MOUSE! HOW SMALL OF A HOLE CAN A MOUSE SQUEEZE THRU! SURPRISINGLY THE MOUSE DID NOT GO THRU A 5/8" ROUND HOLE. A MOLE WAS USED, LARGER THAN THE MOUSE USED, AND MOLE FIT THRU A 1/2 HOLE. MAYBE THE MOUSE WASN'T THAT HUNGRY/DETERMINED. MAN, THEY LEAVE PLENTY OF DROPPINGS. THANKS FOR SHARING!
@@dinagiolo3091 I saw 5 glue tests. Are you sure you searched correctly?
I agree @Matthias Wandel
is one of the best and least bias testers out there.
Also he has two channels, so you might have searched the wrong one. The one is a million plus subscribers has the glue test.
@@dinagiolo3091 i love the music when the mole appears, matthias is such a class act.
Seems to me, that if you use this type of product in high-volume… That if these are the only four products you had to choose from, that the PL premium 3X would be the best value product… Because the pricing versus results is a really good balance.
This was my takeaway also.
Except that PSI per dollar is probably the least important factor in choosing an adhesive. Start out by choosing which chemical formulation is best for the job, and viscosity, and temperature tolerance for curing, and whether it needs be paintable, or low VOC for indoor use, or blah blah blah.
It seems your scale was in KG so the loctite 8x would be about 360 kg that's around 800 lbs
That's a careless mistake
Nice video! Always a fan of your vids. I also occasionally need to use these so its great to know how much bang per buck I get. I also have a small handyman business in ATX and love the leval you build your homes to. Few people care about the quality of their product here!
The more important tests are the accelerated testing in high humidity and temperature. Those tests can be used to predict lifetime of adhesion in an application. Can it still adhere in 10 years in Florida or how about 20 years?
Cleanup between all those is very different though. One can cleanup with water, the other good luck!
glues often have the following weaknesses: high temperature (summer in direct sunlight), humidity, and long term creep. A proper test would apply these factors: ~160°F; 85% rel. humidity (conditioned for a few months), then apply a load for several hundred of hours while still heated to 160°F (~70°C). Of course this is out of the scope of your show, but unfortunately this is also often out of the scope of detectable flaws for buyers of houses or clients.
Also: the glues are called "liquid nails" for a reason: They are strong against in plane shear(like nails) but very weak against peeling off.
What's good for peeling? I have tiles falling from a ceiling
Excellent tension test fellas, Funny note I've been using the 3X for years now for replacing soles on footwear with flawless results. I have a project 20" 2x6 4 ply beam that I'm building in place using (FastenMaster TrussLOK Attaching Multi-ply Engineered Wood Beams) and you just gave me the product that was on my list of adhesives, of course it will be 8x.
Thank you fellas - Van
Hi Van, I know this was an old post but I'm interested in your comment about using 3x to glue shoe soles. Is that man-made soles onto leather? Real rubber to leather? Man made to man made? Rubber to rubber? I'm trying to find a less toxic glue than Barge types. Carol
@@carolrochfort7929 I was using it to resole Crocs you know flipflops. If you're using it to bond leather I'm sure it would be very good, but test glue a sample of what you're gluing. Let this stuff dry for 24 hours.
I use the stuff also to make composite lumber beams.
Theater costumers and cosplay types need to know things like this for repairs! Really excellent question. @@JaymeVanAuken
@@JaymeVanAukenOn similar lines, do you know an adhesive that remains flexible yet keeps it's strength in the hold? Footwear does flex.
@@marymlodzinska4383 I use this same adhesive to put new souls on my wore out Crocs.
Show tests on what most people use construction adhesive for, dimensional lumber to sheeting osb/plywood and dimensional to dimensional end grain and cross grain.
Would love to see the PL 375 in comparison to Liquid Nail not only on strength but also hardening time.
PL 3X is 3X stronger than their basic construction adhesive, probably PL400 subfloor stuff IIRC. Many people say PL Premium is weak mistakenly believe so because they used the subfloor stuff, or the shower contour stuff.
Guess Jordan pulled his folowup video?
Make more samples, load 'em to 50% and 80% of breaking, hide 'em in a closet, and check on New Year Day 2020.
That's soon
Awesome I've been using the right stuff. Pl3 maybe not the top grade but its good enough.
Apparently Loctite's claim is vs standard Liquid Nails. In your testing: PL Fast Grab Premium: 362 kg ÷ Liquid Nails Extreme Heavy Duty 44 kg = 8.23 × adhesion
Some more recommendations Titebond makes a number of different adhesives and Gorilla makes one now. I wander how well Loctite PL200 would compare. It is dirt cheap at $1.50 a tube at Menards.
Really good; thank you
I once used liquid nails on my boat joining transom plank edges and a few other things, It holds but NOT for more than a few years. What will happen is it turns to DUST. Meaning it dries out and then can be pulverized, so it is a failure. Absolutely will never use it again. The PL Poly premium is better but can let go of treated wood sometimes. I have seen cracks open up as the PT wood moisture cycles over years. But overall is pretty good. If you want it to cure thick, mix it with sawdust or some fiber that retains moisture.
I would use 3M Marine Adhesive Sealant 5200 for that application. I've seen tests on "Project Farm's" channel and it was the absolute top marine grade adhesive hands down.
PL Premium all the way!
You didn’t discuss the fact that the urethane adhesives expand. We use Liquid Nails for the fact that it does not expand and we are able to have joints that will not move or “lift”.
3M's 5200 and I think Lowes sells it. Best adhesive, sealant, and caulk......about $10 to $15 a tube, but much better performer.
Appreciate your video. I'm going to be doing some red oak retrofit stair treads (5/8") and risers on top of the current composite stairs. Would you recommend just doing an "S" bead of adhesive, or spreading the adhesive out with a notched spreader?
Good info...appreciate your test!
Great work, guys, but assuming that water based glues "dry" is not correct. The water engages in a chemical reaction.
do a revisit a year from today? to see how they hold up over time?
Thank you very much : I was in that dilemma!
Thank You for the great video and information. Does the Loctite PL work the same an wood to wood? Again Thank You
you guys really need to test better
It's like they don't care about real testing at all. Very disappointing for a *Building Science* show.
For idiots like me, why not Give an example of the right way?
Often times Matt is very careless about controlled & accurate testing in his videos. So lets say: giving the viewer a timelapse video of the controlled environment the product is being tested in ie: temperature, time allowed to cure, exact dimensions of testing area, etc.... This video is one of the better ones for Matt insofar as he posted real numbers, albeit wrong numbers because of the KG to Lb misstep.
One wonders if Matt is just paid by manufacturers to promote products, as opposed to providing real, accurate, data to his viewers. *peace out*
for instance, read the scale right. pounds aren't kilos2. do a wood to wood and metal to metal test cause very few people are using this on wood to metal. you need to give it 1 surface for the glue to be tested. Fro builders I am really worried that they don't know how to test things better for contractors. @@reviewcrewforyou
like now I don't think they had enough water content cause they don't know how to read a scale. Like how am I suppose to trust this guy to build my house?
Used pl 3x on snow guards on metal roof without screws. Wish there was a clear version. Not found yet.
What about cold climate like alaska? 2x4 to shipping container
I would like someone to try Titebond Construction Adhesive PROvantage Heavy Duty in one of these videos. That is all we use (Primarily for gluing down transitions so tons of constant foot traffic). I work at a university where we use hundreds of tubes a year and nothing we have tried has even come close. Titebonds longevity is unequaled in my 10 years working here. But I am open to alternitives. Liquid Nails is garbage. I haven't tried the Loctite PL. We did get some Loctite PL 375 and PL 400. I'm guessing the 400 will work better as it is a urethane and the 375 is water based, but we shall see.
Doesn't say to moisten surface on PL tube. Wish I knew. I left the work out in the rain high humidity and mist for three days now so I hope it finally cured. Prior to that, I actually kept the work out of the rain and it failed, sort of crumbly and moist inside after 24 hours cure on 2x10. I could peal the excess off but not now. Pleased to know the scale was misread.
Matt & Guys, I have smashed 3 expensive glass shelves trying to glue them on an indoor sheet rock shelf. Please, Please let me know what glue to use for the glass shelves to stay permenantly on the the sheet rock. Uzii
So I guess they need to multiply all those numbers by 2.2. Which adhesive you chose depends on what your using it for. Even the cheap one might be more than strong enough for many jobs.
And the strong ones could be too strong
I would like to see the old original Liquid Nails tested. I remember having to tear up a misplaced bottom plate that was glued down and being a huge job. I don't think you can buy the original stuff in all states anymore due to VOCs though.
15 years ago, I glued my boat transom planks using original liquid nails. I thought it was great, BUT BUT, it failed within 5 years later. it dries out to a completely hard substance that pulverizes into dust. NOT good especially for wood and on a boat. Both are moving with moisture cycles. As a glue it is a fail long term.
I use PL Premium 3X on staircase exclusively. It is a great product. Your test results were interesting, however to be truly helpful, as in any accurate test, one should really perform the test multiples times and then compare the average results. It's much more scientific that way.
The PL poly is great stuff but man does it like to run out of the tube on its own even with dripless guns. It's makes a real mess sometimes, especially when you doing more finish like work vs raw framing.
So, I want to put up some guitar hangers in my basement on the concrete wall. I don't have an impact driver and would prefer not to drill holes in the wall I just spent a fortune repairing. Would the Loctite hold well? The hanger is about 1 inch by 2 inches and the max weight of any of the guitars is 12 lbs. The wall is currently painted with a semi-gloss paint. Should I remove the paint where I glue the hanger? Thanks everyone for the help. Much appreciated.
Is it clear,white,black, brown that would have been good to know.
Outstanding
What if or what should I use if I want to stick something to my already title kitchen/bathroom
Did you and Matt test wood on wood?
do some elasticity tests.
got to test "sashco big stretch" for elasticity....
preventing cracks in caulk is a challenge.
I use pl 3x and pl 8x and I know they are very good and I also use sika glue a lot and I want to see a test on sika guys!!!
Good morning, a question, I have a 36-inch diameter round mirror, I don't know exactly how much it weighs but it is somewhat heavy ... I want to stick it to a wooden base, then screw it to the bathroom wall, buy the loctite pl 530, my question is will the adhesive pl 530 bear the weight, or should I get a stronger one? thanks for your reply
nice review
Matt, I’m really excited to see your take on this test! I did a similar video on my channel. Interesting to see you guys test the shear strength of the adhesives! Always pushing awesome content! Keep it up!
Great information. Thank you.
Pl max vs pl 3x? Is it worth the money for the max
Well, 44 x 8 = 352 so the 8x LocTite is roughly 8x "better" than the base Liquid Nails. Maybe that was their base?
Afterdrybing, does the adhesive remains flexible or stone hard? I need the one that is stone hard
Thank you for the great video. Happy new year.
Can liquid naiks be good on trailer house roof
I’d be curious to know how they perform at, or when cured, at different temperatures. This would give us some data to apply for different regions. Here in the NW most of the year they are applied to saturated cold surfaces - not clean warm shop environments.
It should not alter the relative rankings, just require longer cure time.
what kind of adhesive do you recommend for a broken cast aluminum? Someone clipped my mailbox
Could we have a DIY plan for theses amazing wood workstation? Is it your office?
So what adhesive should I use to glue Filon to steel for a camper trailer?
One problem. It's sponsored by a big box store. For an accurate test, watch project farms. He does it right. Just sayin.
What about wood to brick that's what it's mostly used for you can't nail wood to brick or stone to concrete blocks
What is best for subway tile?
Why are you not testing liquid nails fuze it “max”
Confused on how the metal to metal glue up is part of the shear test.
I wonder about in the exterior Florida sun and water over time? Has anybody ever tried to glue 1/2 fence planks to an exterior cinder block wall? I have an old fence and supporting wood columns and cross beams have rotted out. It's also a foot off a cinderblock wall where cats, rats and possums live. I was told I could finish the block wall to my liking but i like the consistent look of my wood fence and i could gain a good foot of real-estate space which I really need on that side. I know I could tap-con some treated 2x4s and then screw the planks in, but I was wondering if I could just glue the 1/2 planks to the wall like panel boards then secure them while the glue clues with some flat concrete nails.
Great video guys! I would call this the "ultimate" strength. Equally important is how it will perform under a lower "fatigue" load with multiple cycles as this will more closely represent the real world situation. You would need some more fancy equipment for this..haha
Can we see a comparison of these adhesives to spray foam adhesives for subfloor adhesion strength?
Spray foam adhesives are relatively terrible for subfloor. yes they can work, but there's your comparison, not even in the same ball park.
Anyone know what the pl max did
The video is private
The link to Jordan's channel is missing... Great comparison video!
www.TH-cam.com/jordansmithbuilds
Will it bond pvc pipe to concrete that well?
To summarize this video- PL PREMIUM is by far the best value out of these 4 glues, as many people have confirmed from experience in the comments below..
Or you could state it the opposite way, that the weakest one is almost always strong enough for the application so paying more is just wasting money. Only a fool would depend on a square inch of an exotic adhesive to secure even 30 lbs. It's more like 1/10th that, most projects don't require more than about 3 lbs per sq inch, but if you feel better paying more for adhesive, hey, it's probably the cheapest extra expense on the job. Frankly there are far more other concerns such as how flexible the adhesive is when cured, whether it can set against non-porous in a large bead, whether it gets brittle over time or with UV exposure, whether it outgasses to expand and form bubbles (and self-extrude itself from the tube even out of the caulking gun to waste some and make a mess), or whether it outgasses water or solvent to contract and pull the work pieces together. The PSI strength, is a very very low importance.