Solar Kiln - Door Construction

[CedarDude]

I'm building a solar kiln and I'm nearly to the point where I need to build the loading doors. Looking for any great ideas on how to build them so they won't sag (much?).

The kiln is a modified Va Tech design, 8 feet x 18 ft., with a door opening on the North side of 16 ft. So I need two roughly 8 ft. doors.

I've built large insulated doors before using a laminated foam core, essentially a modified SIP, and they work very well. But, since the foam can lose structural stability (start to melt) at 165F, I'm thinking that's not a good idea. That's really too bad cause they work well and the weight is manageable. Thought about still doing it and facing the inside with a sheet metal heat reflection shield ... but that's getting too expensive and complicated without a guarantee of success.

So I'm back to a 2x4 stud construction with fiberglass batt insulation. I plan to glue and screw 1/2" CDX onto the frame, both sides which should add a lot to stability but also weight. And I have large 30" strap gate hinges, three per door, with 7/8" pintels that bolt all the way through the wall.

Any other ideas, experience with doors this large? Anyone build kiln doors this big that didn't sag? What about running the interior studs on a diagonal from the bottom of the hinge side to the top of the outer edge?

I'm running the exterior sheathing long, top and bottom, to cover the door gap. Figured I'd put a stop in on the interior with weatherstripping. Any other good ideas on sealing the gaps around the door?

Thanks for any suggestions!

[xlogger]

Maybe make 4 doors on it with the two middle doors have to be set out by hand. I made 5 doors on my 20 ft solar kiln with 3 middle set out doors like planman shows on his kiln design. Little hard but not bad. Or maybe two sliding doors, I'm thinking about that on my next kiln.

[CedarDude]

I looked at sliders but then you lose half the loading space and hard to seal. BUT, yeah, what about four 4ft. bifold doors using standard barn door sliding hardware? Hmmmmm ....

[pineywoods]

I've had good luck with welding up a door frame out of 1 inch square tubing, thin sheet metal pop riveted on the outside and sheet foam glued on the inside. Mine are 2 swinging doors..

[flatrock58]

I am planning my solar kiln and have thought about building a bifold door on a track.  Still working on the details.

[CedarDude]

I've had good luck with welding up a door frame out of 1 inch square tubing, thin sheet metal pop riveted on the outside and sheet foam glued on the inside. Mine are 2 swinging doors..

Seems like that would be the strongest option but beyond me at the moment. Sheet foam is holding up okay with the heat then?

[CedarDude]

I am planning my solar kiln and have thought about building a bifold door on a track.  Still working on the details.

This looks pretty slick ... bifold barn doors:

https://www.youtube.com/watch?v=SX5ahszcJE8

If the bifold doors are going to be inset in the frame, just need to offset the wheels at the top of the door to match up with the track above. The wheel assembly would have to rotate as the door slides. Not sure if you'd need another guide for the door at the bottom? Maybe just a bolt latch to hold it tight when shut.

Where I'm at ...

[GeneWengert-WoodDoc]

The original VT kiln I built and also the one at Colorado State in the 1970s used rear doors with large barn door hinges.  You can find these hinges at many farm supply stores and maybe the big box stores too.  They will work just fine using two large doors.  Just make sure that when they are open, you tie them open if it is at all windy.  With fiberglass, make sure you use a plastic polyethylene sheet on the inside under the plywood.

[CedarDude]

The original VT kiln I built and also the one at Colorado State in the 1970s used rear doors with large barn door hinges.  You can find these hinges at many farm supply stores and maybe the big box stores too.  They will work just fine using two large doors.  Just make sure that when they are open, you tie them open if it is at all windy.  With fiberglass, make sure you use a plastic polyethylene sheet on the inside under the plywood.

Thank you for the reply Dr. Wengert. I do have heavy strap hinges, and have used plastic behind all the interior CDX plywood. I'm going to give the bifold doors a shot since that will also allow me to pull up the trailer fairly close for loading and unloading, and not have to worry about a loaded trailer being in the way of the doors. I built the kiln raised off the ground for this purpose (and heavily insulated the floor). It's easier to build 4ft. doors instead of 8 ft., as well, but will add a couple hundred dollars in expense for the hardware. Seems worth it in this case.

I'll post pictures and info. on the doors. We'll see how it goes.

[rjwoelk]

Back in 86 we built a machine shed and installed 2 bifold doors. Facing them one was 8 ft wide the other 10 ft wide. The 10ft one we put a caster wheel at the center just to take up some of the weight. These doors were 12 ft high 2x6 frame 11/2 inch foam insulation. Worked very well.

[GeneWengert-WoodDoc]

I am not a designer, but it would seem that the door top (called a lintel) needs to be very strong, as when the doors are opening, all their weight wants to pull in the side walls; when open, then push them apart.  You might not have appreciated it, but the plywood adds tremendous rigidity (resistance to wracking).  I might also suggest that the large hinge bolts on the doors, if they do not go all the way through, use a pre-bored hole, maybe 80% of the root diameter.

[Ljohnsaw]

I am not a designer, but it would seem that the door top (called a lintel) needs to be very strong, as when the doors are opening, all their weight wants to pull in the side walls; when open, then push them apart.  You might not have appreciated it, but the plywood adds tremendous rigidity (resistance to wracking).  I might also suggest that the large hinge bolts on the doors, if they do not go all the way through, use a pre-bored hole, maybe 80% of the root diameter.

Without knowing or seeing what you have in terms of framing in the end pieces of the front wall, I'd be very leery of hanging some big doors on that.  As Doc says, a lot of forces acting on that.

What about sliding doors that are hanging from a short chain.  You would slide them closed, lift slightly and push the bottom inside the opening and push the top in until it hits a stop.  Then latch it closed with any number of latch styles.  I like the L shaped sliding bolts used on horse barn doors.  You could make a very snug door and it would never get out of shape.  In terms of skinning the doors, I would use the thinnest exterior ply you can find - 1/4" if possible - to keep it light.  You just need it to contain your insulation.  Yes, you will need to extend the sliding rail almost a full door width off each end supported with a stout post and/or bracing.

[CedarDude]

So this is what I have in mind for the 16' door opening. Seems to solve issues of weight, sag, and the wide swing of an 8' door. Also quite a bit easier to build 4' wide doors instead of 8'. I'm building four 4' doors and using standard barn door hardware to hang the ends of the two two-door bifold 8' sections. Cane bolts will secure the door bottoms.

[vfauto]

How are you going to seal those? ???

[caveman]

We made two smaller doors-one on each end with a removable, insulated panel between them.

  

  

 
We built and installed a bracket to the panel that attaches to a skid steer or tractor quick connect on a front end loader to install/remove the panel.  The panel is too heavy for two people to safely install and remove.  This might be an option if you have a tractor or skid steer available.I don't think I am gaining any brain cells as I get older but it sure does take longer to heal.
Caveman

[CedarDude]

How are you going to seal those? ???

Been thinking about this a fair bit. The doors are inset into the frame as opposed to hanging in front of the opening like traditional barn doors.

If I put 2x6 jamb on the sides and top of the door opening, I can add a 1x2 door stop on the inside and put weatherstripping on that. (I used camper canopy weather stripping under the triple wall polycarbonate panels. Worked great and really cheap ($6 for 30') compared to other stripping, even doubled up it's a lot cheaper)

At the bottom of the door I'm running the exterior siding a few inches long to cover the gap. Was going to run it a little long at the top too but the rail for slider might interfere. We'll see. I could also put weather stripping at the bottom of the door (screwed onto the back for instance) but not sure it's really needed with the siding running long.

I think the big question is whether cane bolts on the door will hold it tight enough against the door stop at the top. I think so but won't know til I try it. If not, there is a hardware option for the inside to do this that's made for traditional barn doors. Whatever I do, I'm sure it will take some "adjusticating."

In other news ... fan shroud and solar fans up. Black metal roofing will go on the bottom of the rafters. I went ahead and painted everything black (aluminum paint followed by flat black) so if I don't like the black metal roofing option I can go without it. Lot of darn painting though!

[CedarDude]

We made two smaller doors-one on each end with a removable, insulated panel between them.

Nice! Like the interior diagonal bracing on the doors. And on a trailer too! I was going to do that and bought a 18' foot trailer for it. But I liked the trailer so much, I went with the non-mobile version.

Panels aren't an option for me but looks pretty slick.

[2StateTrigger]

How are you going to seal those? ???

Been thinking about this a fair bit. The doors are inset into the frame as opposed to hanging in front of the opening like traditional barn doors.

If I put 2x6 jamb on the sides and top of the door opening, I can add a 1x2 door stop on the inside and put weatherstripping on that. (I used camper canopy weather stripping under the triple wall polycarbonate panels. Worked great and really cheap ($6 for 30') compared to other stripping, even doubled up it's a lot cheaper)

At the bottom of the door I'm running the exterior siding a few inches long to cover the gap. Was going to run it a little long at the top too but the rail for slider might interfere. We'll see. I could also put weather stripping at the bottom of the door (screwed onto the back for instance) but not sure it's really needed with the siding running long.

I think the big question is whether cane bolts on the door will hold it tight enough against the door stop at the top. I think so but won't know til I try it. If not, there is a hardware option for the inside to do this that's made for traditional barn doors. Whatever I do, I'm sure it will take some "adjusticating."

In other news ... fan shroud and solar fans up. Black metal roofing will go on the bottom of the rafters. I went ahead and painted everything black (aluminum paint followed by flat black) so if I don't like the black metal roofing option I can go without it. Lot of darn painting though!

CedarDude,

Where did you get your fans?