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Subject: Re: Exterior Door Panel Longevity


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Message Thread:

Exterior Door Panel Longevity

David R Sochar Member

This was discussed a bit on the Stave Core Clean-up thread, but I have more questions, as always.

Does anyone that make exterior doors NOT have a problem with glue joints coming apart? Over the last 45 years I have heard of every cause and every fix, and we still have problems.

I am ready to enact split proof panel assembly in order to get this behind us once and for all. I am also thinking about the Rangate Glueline cutter that will almost double the glue surface, but I know it will be a visual problem in the raises.

I have some 42" doors that will have full width panels about 30" wide. I am going to make them with a center core of 1/4" solid with grain running 90 degrees to two 3/4" plies running vertically. Then a cross band of 1/16" veneer running horizontally. Then faces of 1/16" veneer vertically. A 7 ply panel that is stable. Probably use plastic resin for the veneers, or polyurethane. The panels will raise to fit into a 3/4" plow.

I have done 3 ply panels in the past, and had a few joints try to open, but nothing too serious. In this market, everyone wants full width panels. I do not warrant them, but if there is a problem, I still fix it. If I didn't I'd be out of business quickly.

Photos here are of a 5 ply 36" wide flat panel that went into a 3" x 48" x 120" thick door. After 7 years, they look fine. Glue joints are all tight, but I can see them on the exterior side. South facing, not as diligent in maintenance of the Sikkens as I would like.

Talk about what works and what does not. I think there is room for improvement for many of us.

View higher quality, full size image (810 X 1080)

View higher quality, full size image (1944 X 2592)

6/21/16       #2: Exterior Door Panel Longevity ...
Kevin Jenness


I applaud your efforts. I can't offer any improvements to your method, only a couple of questions.

I have made some exterior doors with back to back wood panels sandwiching a foam core for insulation and to isolate interior and exterior conditions. Do you not consider insulating the panels worthwhile?

"I am ready to enact split proof panel assembly in order to get this behind us once and for all". Is this a legislative proposal, or is your lamination method the enactment?

You may be interested in this thread from another forum discussing exterior door joints (not in the panels) opening up and Joe Calhoon's approach to mitigation.!

6/21/16       #3: Exterior Door Panel Longevity ...
Kevin Jenness

Some more questions:

The photographed panel appears to be well sealed on the edges. Do you use epoxy, or some clear finish?

You propose to make a raised panel for your next project with a 7-ply panel. I assume you will miter a solid wood rim around the laminated panel. How will you join the rim to the panel and the corners of the rim? How do you keep the panel centered in the frame?

In the 3-ply panels you refer to, what was the face veneer thickness? Do you feel that more layers provide more stability? What species do you use for the core, and how do you decide what thickness is appropriate for the various layers? Have you considered using a ready-made panel product for the core such as marine pylwood or Extira?

Are you confident based on experience with using UF (plastic resin)or polyurethane glue for the various panel layers? What characteristics lead you to use these adhesives over, say, epoxy or resorcinol?

What Sikkens product do you use on your doors? How often does it need to be renewed?

I wish I had more to offer than so many questions. Thank you for sharing your experience here.

6/22/16       #4: Exterior Door Panel Longevity ...

Epoxy is good enough to build wooden boats. Once we started using it, we really haven't had any big problems. That said, I don't get to go to many jobsites 5-10 yrs down the road.

The cure times can be long and people always complain about the minute it takes to mix it. As well as the cost. However, knowing that there is a 99% success rate, we choose epoxy.

6/22/16       #5: Exterior Door Panel Longevity ...
John Costin

We have made exterior door panels for door builders that are Extira with a wide lumber rim for raising, veneered with 1/16" veneer. We use epoxy for the veneer adhesive only because of Resorcinol's objectionable "graple" hue -- I share Dave's concerns about epoxy and solar heat.

Unfortunately, because we didn't do the doors I haven't been able to observe the panels in the field, but they have been out there at least four years and I haven't heard anything back. Not the best method of tracking, but bad news tends to travel fast.

I'm not sure why a multiply of veneer and/or lumber would be superior to Extira, but I'd like to hear the thought process if you believe it to be so. Like you, Dave, we're committed to finding or developing the "best practice" in this field regardless of the perceived hassles.

John Costin
Veneer Services Unlimited
Custom Veneered Components for the Woodworking Industry

6/22/16       #6: Exterior Door Panel Longevity ...
David R Sochar Member


The panel in the photo is sealed with West epoxy on all the edges. It sits in a frame with large bolection moldings on both sides, and was not glued in place, but was sealed with RTV silicone. A stable panel could be glued in place, but never removed if there were serious problems. This one was given an 1/8" all around.

When doing the 7 ply panels, there are face veneers and crossbands, all 1/16" thick, and the center ply is solid wood, same species, about 1/2" thick. No solid rim mitered around. The panels get a 3/4" tongue into the frame plow, so the raise shows nothing much except a slight line at the panel face from the cross bands.

We have done the mitered rim, but then it is more parts, more glue joints, more prone to problems?

Extira is not my favorite material by a long shot. No real complaints except that it is MDF, not solid wood, and we tell customers that the doors are solid wood. Real wood. I also don't trust materials other than what I have control over. Odd, yes, but that is how it is.

I used to do a three ply panel with a center core of 1/4" ply, and thick faces - 1/2" to 3/4". Some of the exterior side glue joints tried to open, but there were never any call backs. Not quite by the rules, but they worked - I think. I got away from them during a purist phase when I reasoned that solid wood was fine. Once the panels split, the purist in me is driven back into the shadows.

I would say that more plies are more stable - look at commercial ply.

I know the Gorilla glue for veneer faces is not the first choice for many, but I like the penetration, the spreading, the adhesion and the workability. It is a 'solvent based' glue, so little to no water. It also presses well. Plastic resin must have 70 plus temps, and I like things about 62. Epoxy is good for lots of things, but back when we were making wood tops every day with epoxy, we found out that it must have a thick glue line and low clamp pressure or the joints can starve and open. Hard to do with all those strips of wood. I used to use Resorcinol in the 70's, and keep threatening to get back into it. It is probably the best choice on characteristics, but it also must have higher temps, likes pressure - that a vacuum bag may not deliver - and has that purple line.

I have a collection of about 20 assembled wood samples with various joints and laminations that has been laying in or near a drainpipe for 12 years - ground contact, vegetation, etc. The 3 ply panel with commercial 1/4" core has the core mostly rotted away, but the Mahogany is still sound under a 1/16" of gray weathering. Results are not organized and too extensive to go into here. Besides, I'm not sure now much they bear on the wood panel joints failing.

I looked back into heat problems with epoxy and found more references that said it was fine with higher temps than said there were problems. Boats get it all, and epoxy holds up, so that would not be rejected for temp/strength restrictions like TBIII.

Back to Back panels - with or without an insulating panel? When I started my own shop in 1990, some of the first work I did was replacing panels in doors made that way. The guy that made them originally refused to fix them after a year or two or three. So I got the work. I looked at those weasely 1/4" thin tongues and open joints and reasoned that there is not enough wood to hold things together. It needs more glue surface, since that is what glue wants. Is that rational? I don't know, but it has kept me from going down that path.

The 7 ply panel I describe is what I think is the best panel I can make, given what I know now. Subject to change.....

6/22/16       #7: Exterior Door Panel Longevity ...

I did a bit of testing and found that Extira has about twice the movement with changes in moisture content as ocoume marine ply.

It seems to me that well made marine ply should serve as well as a core stock as a shop made laminated panel. If you glue up a 7 layer panel is it still "solid wood"? David, do you use a more rot resistant material than ocoume for your cores? What sort of 1/4" ply did you use in the 3 ply panels you refer to?

6/23/16       #8: Exterior Door Panel Longevity ...
David R Sochar Member

I look at the 7 ply panel and I would treat it as a man-manse panel product. That is, it is like plywood or MDF in that it is stable, can be rimmed with raise moldings, glued in place, etc.

I have seen lots of panels made with 5 ply - solid cores, thick (1/16"+) crossbands and then faces. Everything from Singer Sewing Machine table tops to old-style lumber core plywood. But in interior use....

6/23/16       #9: Exterior Door Panel Longevity ...
John Bishop  Member


Your process is awesome. We make a lot of exterior doors here and whenever we have had an issue itís always the same. An uncovered fully exposed door system pointing in the wrong direction for exposure.

I no longer will guarantee exterior doors that do not have some type of shelter. You will not find a quality older home anywhere with this affect; the doors always have some shelter never fully exposed.

I am sorry; it was finish failures that caused separations from being fully exposed to the weather and the sun.

Good luck


7/30/16       #11: Exterior Door Panel Longevity ...
mildredbrivera Member

Great post!


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