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  Stitched Miters & Butt Joints  
 
By Aaron Foster, a finish carpenter in Southern California

Most of the casing I install is too small for biscuits, and much too small to use a Clam Clamp. I've always wanted to pre-assemble these smaller moldings, just like I do large casing. But I don't have time to glue up the joints and leave spring clamps on until the glue dries. If you want to pre-assemble smaller casings, as well as crown, base, jamb extensions, try this technique. You'll be amazed at how easy it is, and how well it works. And if you can't afford enough Clam Clamps (they're $55.00 each!), remember this method works even better on hardwood and larger casings. On a recent job, I assembled 20 sets (after all cuts were made) in about 45 minutes using the stitch method. I would have needed a 'ton' of clam clamps to move that fast, but all I used was a $150.00 stapler and about $1.00's worth of staples.
 
 
These are the tools. 23ga micropinner (left), 20ga 1/2" crown pneumatic stapler loaded with 3/8" long staples (center), T-50 compatible 3/8" crown manual stapler loaded with 1/4" long staples (bottom right), and a glue bottle (top right).

 

 
1) Start by applying glue to the surfaces to be joined.

 

 
 
2) Use the micropinner to pin the inside and outside of the miter to keep the face of the joint registered until the glue cures.

 

 
3) Staple the back of the casing as shown with the 20ga pneumatic stapler (the same type of stapler/staples used for applying flashing paper or stapling upholstery). This type of stapler uses the flat-style staples. This is important as the flat staples do not countersink and thus do not set deep and blow out through the face of the moulding. Do not staple in the thin part of the profile or the staples will penetrate the face of the molding. Trial and error (guess who's?) has found the 3/8" long staples to be the ideal length. Any shorter and they don't hold well. Any longer and they are more likely to blow out the front of the molding. This step is important as the strength of the joint is created by the staples bridging across the seam and acting like mini clamps. The staples also create a pivot point that forces the face of the miter
to close tightly as the casing is nailed onto the wall. In situations where the drywall is 1/16" proud of the jamb, the staples actually suck the miter unnaturally tight as the assembly is nailed to the jamb, which makes this technique ideal for all those times when you need to beat drywall to get the casing to contact the jamb. If you use enough staples, the joint will never open.

 

 
Normally, I do not flip the assembly over to staple it. Rather, I find it faster to nail the back of the molding upside down by hanging the corner off the edge of the assembly table. This particular type of molding (lightweight mdf) is very prone to splitting and flaking, so even the micropins caused cracks between the flake layers and had very little hold. However, the staples hold extremely well in lightweight mdf as they do not penetrate the edge between layers but instead the
staple points are penetrating the face - a much stronger hold with no splitting. This is significantly quicker than biscuits with no down time waiting for glue to dry. Also, no miter clamps are necessary, saving a step and time.

NOTE: The manual stapler can be used for this step if the appropriate pneumatic stapler is unavailable

 

  
 
4) This is an optional step, but I like to use it on mdf moldings as a little insurance until the molding is carried to the opening and installed. Use the manual T-50 stapler to put one or two "temporary" staples across the exposed face of the miter. The temporary staple(s) act like mini clamps and help to stabilize the joint while you carry the assembly through a house and potentially bump into walls and obstructions. The reason I prefer the manual stapler with 1/4" long T-50 staples over the pneumatic stapler is because the lower power of the manual stapler won't leave a driver blade mpression on the finish face of the material. After the molding is installed and nailed off, the temporary staples pop off with the orner of a chisel leaving behind two very small holes that require minimal filling. On stain grade, I'd skip this step to avoid extra nail holes. Besides, on stain-grade work, the micropins hold much better so this step is unnecessary.

 

 
Voila! You have just created the superman of miter joints. Though the glue is still wet and only staples and micropins were used, this joint easily supports over 5 feet of casing hanging in mid air! Now the final step is to spread your assembled casings to their respective openings. To prevent a miter from popping open during transportation,always
carry the assembly "sunny-side down". By twisting the casing so that the bottom aims slightly up, you create positive tension on the staples which forces the miters closed.
 
I also use staples to stiffen up large jamb extensions, too. In this photo I've stapled the the butt joint in a frame.
Once all four butt joints are stapled off, the entire unit becomes rigid. First, I use 18ga brads to nail the jamb together, then it only takes seconds to staple all the joints. This technique prevents the joints from developing gaps from racking during transportation.

 

 
The photo above shows how the staples can be applied in areas that will later be hidden by casing (beyond the reveal) or on the back of the extension jamb.

 

 
I've mated these two boards side-by-side (and penciled over the joint for clarity). If you staple perpendicularly across the joint, the seam will stay closed but can shift and slide, causing a mis-registration of the two pieces. Instead,
staple in a zig-zag or X pattern and the material won't be able to shift. Combine both square and zig-zags for the ultimate in strength and stability.

 

 
My favorite place to reenforce joints with staples is on outside corner crown miters when building templates or preassembling. The joint was first assembled with glue and micropins. To prevent the the outside point of the miter
from ever opening, I shoot a couple of 20ga staples there. The staples are on the surface that will contact the ceiling and so they will never be seen after installation.
 
But to really beef up an outside miter, run a row of staples right in the crotch of the miter on the back side of molding, taking care not to staple in thin part of the profile.

 

 
I also like to make crown corner templates for laying out crown on inside and outside corners, rather than using gauge blocks. I use gauge blocks, too--sometimes, but because drywallers build up the mud so much at the corners, gauge blocks are never very accurate. The template I use ensures that the corners are laid out just the way the crown will sit, so all the miters are tight. I snap chalk-lines at these marks prior to installation. I used to use glue and brads to make these templates, but if I didn't wait for the glue to dry my corner templates would fall apart; even if the glue did dry the templates would break if I dropped them from a ladder. Now I staple the inside and outside of the miters and the templates are indestructible.
 
 
     
     
   
     
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