I need to build an arch top 3' x 8' entry door for a customer. This will be a painted unit. I'm wondering if I should be using fir or clear pine, or a suitable hardwood for the construction. Also, I am wondering if I should stave and laminate the stiles and rails, or go with solids. Any advice on this would be greatly appreciated.
(Architectural Woodworking Forum)
From contributor H:
I like mahogany as the best choice. I think that mahogany and white pine are the only safe choices without building a laminated door like you mentioned. The thing about todayís white pine is its too soft (grown too fast) and therefore vulnerable to water damage if it goes un-caulked and properly painted and allows water to get behind the panel mouldings and sit there.
Iíve personally never seen mahogany rot and its wonderful for staying straight. I been experimenting with lyptus as a lower cost material similar to mahogany, but the jury is still out on it. Keep in mind that it is heavy to work with and hard on knives.
My advice is to get the primer on all available surfaces before assembling the door. Bed the panels in acrylic caulk (don't use silicone for obvious reasons) when you assemble the door, then paint all surfaces. If the door is to be stained, apply the basecoat (Cetol 1 or similar) before assembly, use a brown caulk for minimizing color grin, then apply the finishing coats to all available surfaces, especially tops and bottoms.
We like solids, but remember any core you use could become the weak link, bond-wise. Use long tenons, fully coped and stuck with integral profiles (no tacky moldings), and make the panel joinery wide and tight. Any glass needs proper sealants/clearance. Upgrade all the hardware, especially the hinges. Upsize the jamb and plan on cutting in a W Oak sill into the sub-floor and bandboard. Plan now for weather-strip.
The talk about overhangs is correct, but you usually aren't consulted about that, so have no control. Use the proper glues and don't believe all you hear about water resistant. Check the finishing forum for a horror story on finishing exterior entry.
Doors are the most difficult, problem prone articles of wood other than boats. Unlike boats, when a door fails, they call you. Boats sink with their owners. Both (doors and boats) require periodic maintenance based upon exposure and environment. Professionals need to be involved. If it is your own door and you are willing to put up with any shortcomings, fine. If it is for hire, consider your liability and responsibility.
Mahogany and oak make poor paint grade doors because they have open grain, and do not paint to a smooth surface. Cypress is specified occasionally these days because it is very rot resistant, but it doesn't paint all that well. Poplar paints and machines well, but it is very susceptible to rot. Never use it outside. I've encountered white or red cedar doors occasionally and they are extremely rot resistant, and paint beautifully if you seal the tannic acid in the wood from bleeding into the finish.
Oak is very strong, wear and rot resistant, and is customarily used for the threshold. It is often simply sealed with boiled linseed oil, or painted black. The advice to prime the panels before assembly is wise. There are many silicone modified latex (acrylic) caulks available that will accept paint. Never use pure silicone caulks.
Paint is essentially 100% UV and water resistant. If the coating is kept in reasonably good repair, (repaint every 4-6 years) the door will last ages. I have worked on scores of painted exterior doors over two hundred years old, still in good shape.
Doors always last longer if the finish on both sides is the same, (not paint inside and varnish outside) and you paint the top, bottom, hinge butts, mortises, etc. as well. Even if the finish paint specified is latex (or acrylic,) prime it with exterior alkyd primer.
Comment from contributor A:
Poplar is great for painted units. Maple, in high humidity areas is notoriously reckless in regards to expansion and contraction. If you choose maple, do not sand too fine, or you could have adhesion problems with your finish.
On core: we use a pine core made in Idaho. It is light and sturdy. The ends of the short pieces are not finger jointed, but staggered. Warpage is a rare issue. That stave core reduces expansion and contraction is a myth. Example: If you make poplar stave core, it will behave as solid poplar on the volumetric parameter. It will however resist warp and twist due to the multiple glue interfaces. From a production stand point, we use stave core for two reasons. One for the resistance to twist and warp, the other for the reduction in hardwood used to build a door. You'll have to weigh in your labor costs on the process to see if it is economical on short runs.
On tenons: I have been using Freeborn stacked cutters forever. Standard on a 2 1/4" door is a 3/4" deep x 1" thick tenon, regardless of the pattern. I use Franklins Titebond Original, and have never had a door fail.