About 3 years ago, we started having problems with exterior door panels opening up at the joints when we glued for width. We were using TiteBond III, thinking it the best for our application.

After repairing/replacing about 12-14 door panels, and $14,000 worth of effort, we probed a little deeper after we cleaned the shop of any TBIII.

We learned from the techs at Titebond that TBIII looses strength as temperatures increase. At 180F degrees, the glue looses about 60% of its strength. Go to 190F degrees, and it is about 80% of its strength. The glue does not regain its strength as the temperatures return to a more normal range.

The panel photos below typify what we found when we removed them from a door. These are flat panels, 1-1/2" thick, two plies for thickness, with epoxy sealed end grain. I admit it was hard to believe.

The first photo shows a white line in the black field that is the indicator of a failed joint. Just open a slight bit.

The second photo shows a cut out part of the panel. It is two ply in thickness, with the joint to the exterior the top. It is failed, with glue residue in an orange color. The wood broke in the second plies' thickness, showing the split, lighter color wood. This indicates the glue failed halfway thru the panel - 7/8" at this point.

The last photo shows the joint where the glue failed and where it held. The inside of the door was much cooler, and the heat from the exterior hot face penetrated about three quarters of the way thru the panel - all except for that last bit on the lower edge.

The problem panels were all dark. All faced East, with just one or two facing West. They were all Honduras Mahogany. They were made over the period of 2 years.

View higher quality, full size image (636 X 526)

View higher quality, full size image (900 X 540)

View higher quality, full size image (900 X 529)

David,

I've never been a big fan of TB3. I've found it too expensive and with no benefit over TB2 other than it is water "proof" instead of water "resistant"......i.e. submersible. I've never felt a need for anything I've made to be that waterproof.

I feel for you in this situation. I had some curved base fail once because of a delaminated bending ply backer. It was a poor choice on my part but I was trying to save the customer some money using the ply backer instead of solid wood.

Neither the plywood distributor nor manufacturer would discuss the matter with me. In the end I turned to my liability insurance company for coverage on the repair. They were very good about it and covered the loss. It was the only time in 30+ years that I turned to insurance for any sort of business problem.

Good luck,
BH Davis

Sorry to hear the extent of your TB3 whoas. You've alluded to the failure over the last year. This is the first time I've read the specifics.

I bought one of the small bottles of TB3 when it first came out. I didn't like it from the start. We didn't even finish the bottle. Gorilla Glue left the shop after one year of little use.

TB1 & epoxy(MAS, West System) only in our shop. TB1 is one of the few glues I've ever used that doesn't telegraph thru a really good paint job. Epoxy is the ideal waterproof wood glue. More expensive. More wasteful. Mixing takes seconds. At the end of the day the epoxy won't fail. However, we may fail in our construction method.

I had the exact problem with a door using the same glue.
The good news foe me the door is mine .What I found as soon as the door gets hot with the sun the glue melts gets soft
The glue I used for my exterior doors is Elmer's Probond Max Wood Glue
Very thick glue gets in the pours no problems

I've had the same problem with the veneer seams on the bottom rail of two doors. I glued the veneer seams with TB III and then glued those panels to the stave core with Plastic Resin Glue. These were wide rails at around 12" so each veneer was around 6" wide. Within a year both split right at the veneer seam. They didn't bat wing open proving the PRG was still holding each piece to the stave core; they just opened up at the seam like shown in your first photo. On one door I replaced the bottom rail. On the other I forced some finish into the split to hopefully preserve the integrity of the finish, and we're just watching to see what happens.

John

While back here i posted about a set of cabinet doors that a customer picked up and left inside his truck with the windows up in the sun for over half a day even after i specifically told them to not let them sit in the heat. All the panel joints opened at the ends. This was with Titebond Original so i know Original loses its strength when exposed to excess heat too.

TB 1 is a heat responsive adhesive. You can use it as a veneer contact cement by applying it to both surfaces, letting the glue dry, putting the pieces face to face and then heating the glue with an iron. The glue will soften under the heat and the two surfaces will bond. This is partially why it is a poor choice for the Workrite wood welder which in effect heats the glue to cure the joint. TB2 on the other hand hardens with heat which is why it works so well with the Workrite.

BH Davis

We had a similar issue as the doors left in the car with TBIII. We cnc'd some plaques for a wholesale customer that were painted black on blanks laid up using hard maple with TBIII. They have a retail shop and we have repeatedly made it clear that putting them in their store front glass display case in direct sun was a guaranteed failure. One of the owners picked up the plaques and left them in the front seat, windows up, on a 90+ day in the full sun. Every glue joint failed and opened for inches on the ends. We spring joint hard maple almost daily and have never had a failure.

We credited the job and replaced with the customer after they somewhat insinuated it must have been a manufacturing issue.

When we replaced them we laid up three more identically and put them on the front seat of my car in the sun on a similar day and within 4 hours they failed identically.

We very rarely need water proof glue. As it happens I'm about to start on a porch rail & balusters for my own house. I used to always use resorcinol phenol formaldehyde for exterior work. Totally water proof, expensive. About $130 a gallon! So I was considering TB3. Thanks guys, you talked me out of TB3. Porch project will be Cypress.

We recently had similar issues with a couple of our entry doors in the field. In all cases, the doors faced the afternoon sun. Panels either showed the glue lines or the panels were cupping.

We built our panels out of solid lumber and edge glued it with TBII.

Due to the recent issues, I have been feverishly trying to trouble shoot and correct the issue. I also have spoken to technical service at Franklin Adhesives and they also told me that TBII or TBIII lose its strength at around 150 degrees. They mentioned that we needed to use a more industrial type glue to hold up against the heat as well moisture. Tech. support suggested using Advantage 405. This is a two part glue with a catalyst.

I also spoke to Spectrum Adhesives, and they have sent me a sample of their equivalent of Advantage 405 that is a one part glue. We have not had a chance to try the glue from Spectrum as of yet.

Both Franklin and Spectrum said that the issues that I was having was due to too much moisture in the wood we were using. We usually make our exterior doors from Sapele Mahogany. I checked our current inventory and it was around 10% MC according to my pin tester. It was a little higher than the 6 - 8% that is suggested. We are keeping our eye on this.

We also looked into the construction of our doors. With Dave Sochar's input, he suggested that we build our doors using what we call a "clamp glazed" door. We are currently stopping in the panels from the interior of the door. This new "clamp glazing" construction would prevent the panels from cupping due to the tight fit. My guys in the shop are not convinced this is the direction they want to go. They believe that if we make a good panel, it should not have issues.

We are currently fabricating our panels differently. We are now sandwiching a piece baltic birch plywood with a skin of edge glued sapele on each side and gluing the sandwiched pieces by using a vacuum bag. We are thinking the plywood will give us a more stable panel. We are using the Advantage 405 right now but planning on trying the Spectrum glue in the near future.

We also set our panels in a bed of caulk and press it into the caulk. I am now looking for a new line of caulk that can also withstand the heat and moisture. We have recently moved to Tremco Dymonic FC after the quality issues but we are considering moving to NP1 or a caulk from Applied Adhesives. Looking for other suggestions.

We Have not had any issues with TB3 but watching this thread closely. Early on we tried some catalyze type 3 glues but they were too fussy in our small shop with temperature and shelf life issues.

TB3 is very inconsistent. We buy in 5 gallon pails and used pressurized gluing. It is thick and thin and sometimes lumpy. We usually stir it before dumping in the pot. It will come apart when soaked in a bucket of water but doors and windows are usually not subject to this.

I am looking into trying some of the PVA glues Jowat offer for exterior work. We use a little epoxy on high risk work but would not like the hassle of that for everyday jobs. It’s my understanding that epoxy will come apart with high heat if not heated during curing.
Our exterior panels are always double sided and glue joints reinforced with splines, t&g or glue joint cuts. Wide solid panels are always at risk. Panels are set like IGU on our Euro doors but still do some captured panels on traditional work.

Good development, gentlemen. Now.....we wait.

The ply center and two solid faces is the panel design Simpson Door used for its 'split-proof' panels years ago. They may still use them - it would be interested to see if their process has evolved any beyond that. Widest panels were about 26".

I think the 3 ply, stable center, solid faces is a good way to go until you get up to wider panels. We often see 32" wide panels, up to 40" or more. That kind of width will present a problem for the 3 ply panels, my opinion.

This is why we have developed the 7 ply panel, an effective piece of plywood that will not move, and can even be glued into the door assembly.

We are adding insurance by getting a glue line jointer for the Shaper (as Joe C mentions) that can effectively double the glue surface of a panel butt joint. (Rangate and Amana both offer their version of the cutters)

Currently, we are using a RTV Silicone for our glass and/or panel caulking. "RTV" means "room temperature vulcanizing". I prefer all my vulcanizing at room temp. This has been 100% trouble-free.

Chad, if I understand you right you are making your panels with a plywood core and solid wood glued to it on both side; is that correct? If so, that will be a recipe for failure if the door gets any direct sun. I made some floating panels only 6" wide with 3/4" Baltic birch and 1/4" veneer on both sides. They all split on the outside in the first Winter from direct sunshine on the door. I replaced them with panels made from two separate solid wood pieces separated by aluminum foil. So far, so good. I did another door with back to back solid wood panels over 12" wide. That door gets massive amounts of direct sun as it faces due West. Two years in all is well.

John

Hi John - that is how we fabricated the original set of panels for the door. They cupped and allowed water in through the sticking.

We are getting away from fabricating two separate panels because we feel the glue line is too thin to hold up in an exterior application.

Are you saying that since the wood was glued to the plywood core it has no where to go (expand or contract) ?

Did the wood to the exterior just crack or did the entire panel crack?

Did you check the moisture content of the wood before fabricating?

Making a panel out of one piece of wood is nice because you don't have any glue lines, but we rarely have doors with that narrow of panel.

Chad, only the exterior 1/4" veneer cracked on those panels, not the plywood core nor the inside veneer. They cracked right in the middle of the width, as you might expect. Those panels were glued up in a vacuum bag using plastic resin glue. The moisture content of both the plywood and veneer was 7 - 8% during fabrication in my climate controlled shop.

I haven't had any back to back solid wood panels crack, but all are one piece and not more than 13" wide. I try to design doors with one piece panels to elliminate glue joints, but if I ever do have to make glued up panels I will use plastic resin glue, or some other catalyzed thermoset resin, so that it is stable up to at least 200F.

I don't think cupping will be a problem if you use back to back floating solid wood panels separated by a moisture barrier, even for wide panels. If the MC is constant across the panel it shouldn't cup. The problem comes when you use one piece panels where the RH is different on the inside and outside, as it will be with an exterior door. Those will almost certainly cup, no matter how you try to hold them in the frame, and if you figure out a way to hold them so they can't cup they will crack. One way or the other, they have to relieve that stress.

John

So what I am learning from this post is that the glue you use is pivotal on exterior doors and even more pivotal is the size of the panel. We have a hard time saying no to customers but we are going to have to evaluate our policy on how big of panels we allow. This will limit our door designs.

I am still confused by how to make a trouble free panels. We will not go fabricate back to back floating solid panels because of our past issues. I like Dave Sochar's idea of 7 layers, but that will take a ton of time - that is why we decided to use baltic birch plywood for the core.

John, what type of PVA glue are you using and do you lay your panels into a bead of caulk?

"We have a hard time saying no to customers..." I know the story. I added a line to the warranty to exclude wide panels and iff had no effect on customer's preferences. Warranty or no, they wanted it.

What I am being drawn to is a complete rewrite of the 'rules' about cross grain gluing. I break the rules all the time, with no unfavorable consequences. Thousands of others do also. Also how do describe what we can/cannot do, and what mechanisms are the ones making this so? Do I have to start all over and relearn this craft?

Chad, David and some others here have a lifetime more experience than I do with exterior doors, so their advise should carry a lot more weight to you than mine. That said, what I've seen is what I've seen, and 32 years as a practicing engineer gives me some basis for understanding the forces in play with most any application.

I don't use PVA glue to glue up panels. I have not yet used a glued up panel in an exterior door and, hopefully, I will never have to. If I do, I will use plastic resin glue to glue them up and I will use 2 floating panels separated by a vapor barrier.

From looking at many, many doors, some not very old to ones hundreds of years old, there is a high rate of failure in wide panels. I will avoid using them if at all possible, including turning down work if I can't sway the customer to let me use narrower panels. I'd rather walk away from the job than worry about it failing. Been there, done that, and don't want to do it again. Customers want what they want, but no one wants problems. You will be the one stuck with the problem when it happens. Even if you get the customer to sign a contract with no guarantee, your reputation will take a hit. And I'll bet if you have any passion for your work you will feel responsible to make it right no matter what the contract said. Better to stand your ground or walk away.

John

John - Good luck with limiting your builds. If you can do that and keep everyone happy, you will be ahead of the game.

We have 4 people to satisfy: Owner, Builder, finisher, carpenter. Then we are happy - so 5 in all. If anyone is unhappy, or less happy, it is Acorn. The joy of owning your own business.

I look at my upcoming, and I have 7 exterior doors coming up. All are one panel wide. Panels are to be 24" to 38" wide. These are all doors designed by others - architects, design professionals, or even the homeowner. To go in and try to get them to change to two narrow panels just will not work. Too many people, too little understanding. Some designs just can't change. I enjoy educating, but it has to be short and simple and then only if they ask for it.

I understand David. I don't have to eat from the work I do, so that gives me more liberty than those who do in what jobs I take. I would be happy building doors with wide panels if I had confidence they wouldn't fail. But after looking at literally hundreds of doors, here and abroad, I don't. The only ones I'd take right now would be if the door sits behind a covered porch, and never gets direct sun.

So what's your plan for those wide panels? Solid wood or some kind of composite? Whatever you choose, I hope the construction allows for the panels to easily be changed if necessary.

John

We tried to build some panels with a plywood core and we got some separation of the glue joints.

The plywood core is Baltic Birch and the skins of the panels are White Birch. Plywood is 3/8" thick and skins are 1/16" thick on each side.

The panels are for a 2 panel craftsman style door, 13-1/4" wide by 50-3/4" tall, 1/2" thick for a 1-3/4" thick door.

Trying to figure out what we should do next with building panels. Our first problem was with our panels cupping. Now it seems like they are cracking.

We would normally build two panels for each opening and set them back to back. We had issues with panels cupping so we moved to a new construction process of using plywood in the middle to keep the wood more stable. Now we are facing cracking the panels.

We are now thinking of going back to gluing up boards to get one solid panel.

We are using Franklin Advantage 405 glue. It is a two part glue.

I would be interested in your thoughts on how you would try to solve this issue we are having.

View higher quality, full size image (1008 X 756)

View higher quality, full size image (756 X 1008)

View higher quality, full size image (756 X 1008)

Chad, I don't think the glue is the problem; rather, it's the one piece panels with a BB core. I had much the same failures with some white oak veneered Baltic birch panels I made for an exterior door. The veneer seams began to split in less than a month after installation, pretty much as soon as we had a few sunny days and really cold nights. I replaced the panels with solid back to back panels, separated by a layer of aluminum foil and so-far-so-good.
My feeling at this point is to use solid panels with as few joints as possible, none being best. If you make glued up panels the glue needs to be capable of holding up against water but also high temperature. Yours may be, I just know the particulars about it. Also, I think it is very important that the back to back panels be separated by a vapor barrier, as this will keep the moisture content more constant in each panel and help prevent cupping. Quarter or rift sawn stock will tend to cup less than plain sawn, too.

John

Chad,

Your panels failed because 1/16" thick veneer is still lumber.......albeit thin lumber. This is why commercial veneer is sliced off the logs at a typical .024".....that's less than 1/32".......or even thinner. Even at .024" thick once applied to commercially made panel stock it will get even thinner after sanding of the panel.

Your 1/16" thick material acted just like any solid board would act when glued over 2' to 3' width.........it shrunk. The substrate didn't shrink and hence the cracking.

I don't speak all this arrogantly but rather humbly from first hand experience !

BH Davis

Woodweb discussion on veneer thickness