Corner joint for porch or deck railings

[Anthony Whitesell]

I'm in the process of finishing the new porch. The final step is the top railing. I'm trying to decide what joint would be best for the corners. First thought would be miter. But I have heard, and seen on the old deck railing, the miter cut is not the best option. I was thinking of half lap or half lap miter. The concern with either half lap joint is trapping water between the overlapping portions and causing the wood to rot more quickly.

So my question to the resident experts, what corner joint would you recommend for the deck top railing?

[Von Bickley]

I would use a standard half-lap, but I am not an expert.

[andy bessette]

Miter with full length slip feather epoxied in.

[Anthony Whitesell]

Miter with full length slip feather epoxied in.

Like the bottom picture (or even second to last)?

http://www.craftsmanspace.com/knowledge/mitered-woodworking-joints.html

[andy bessette]

Like the bottom photo. The slip feather grain runs perpendicular to the miter joint. And the slip feather is nearly as wide (across the grain) as the miter. Extremely strong.

[Anthony Whitesell]

How would you make the cuts on the end of 2" x 8" boards 8 to 13 feet long? I'm thinking the tablesaw jig and dado blade are out of the question.

[andy bessette]

Radial arm saw.

[Anthony Whitesell]

Radial arm saw.


???

Plus I don't have one.

I thought about the bandsaw (forgoing the fact I haven't a clue how to control a 13' board during the cut), but I don't have a way to chisel out the center. Too deep for the chisels I have or have access to.

I have been contemplating the spline reinforced joint (second to last) and cutting it with a spiral bit in the router.

[lowell holmes]

Check this out.

http://www.gottagodoityourself.com/a-most-interesting-wood-joint/

[Anthony Whitesell]

A+ on the coolness factor. But I'm not seeing it work on a 2x8 deck railing.

[Jim Morgan]

How would you make the cuts on the end of 2" x 8" boards 8 to 13 feet long? I'm thinking the tablesaw jig and dado blade are out of the question.


Use a router with a slot-cutter bit.

[andy bessette]

...I don't have one...

No excuses. :)

A radial arm saw is elementary and has been an essential machine in my shop for many decades. IIRC I paid $250 for my ancient Craftsman RAS and would never be without one.

[Anthony Whitesell]

Use a router with a slot-cutter bit.

I think I would want a slot wider and deeper than a router slot cutter would make (emphasis on the depth).

[Anthony Whitesell]

No excuses. :)

A radial arm saw is elementary and has been an essential machine in my shop for many decades. IIRC I paid $250 for my ancient Craftsman RAS and would never be without one.

You're right. It is an elementary tool. But moot. I don't have one, don't have access to one, and don't have room for one. Beyond that I'm not seeing how it would make the cut on the end of a 8+ foot long board.

[andy bessette]

...I'm not seeing how it would make the cut on the end of a 8+ foot long board.

Come on!

The head is tilted 90 degrees such that the blade is parallel to the table. The long rail is clamped to the table at 45 degrees (or whatever miter angle) to the track, and the blade is drawn through the rail end.

But you don't have room and so don't have one. So you'll have to make a jig for a Skilsaw.

[Anthony Whitesell]

Come on!

The head is tilted 90 degrees such that the blade is parallel to the table. The long rail is clamped to the table at 45 degrees (or whatever miter angle) to the track, and the blade is drawn through the rail end.

But you don't have room and so don't have one. So you'll have to make a jig for a Skilsaw.

I forgot the head can rotate that way as well.

[Joe Wood]

We almost always use a miter with spline, cut with a slot cutting bit. This is an ipe top cap.

Make sure the spline is cut from face grain stock and not quarter sawn!

366512

366513

[Anthony Whitesell]

Make sure the spline is cut from face grain stock and not quarter sawn!


Can you elaborate? I know what quartersawn lumber is. I've never heard face grain stock before. I have use quartersawn, riftsawn, and flatsawn to make splines. So long as the grain is perpendicular to the joint, what does it matter how the lumber is cut?

[Jim Morgan]

I think I would want a slot wider and deeper than a router slot cutter would make (emphasis on the depth).

Something like this https://www.amazon.com/Yonico-14182-Biscuit-Jointing-Carbide/dp/B00KZM1Q1A/ref=sr_1_2?s=power-hand-tools&ie=UTF8&qid=1503342155&sr=1-2&refinements=p_n_feature_keywords_browse-bin%3A2805197011 will cut a 1/2" deep slot. You could substitute a smaller bearing to get a slightly deeper slot. With a tight fitting spline (grain running across the joint!), there is really no need for greater depth. The slot can be started and stopped so the spline is not visible after the joint is assembled. Or if you have access to a Domino, you could use that.

[Anthony Whitesell]

I didn't say I didn't have one. I have a slotting bit that does 1/8" wide by 3/4" deep. The feather method andy mentioned would have a much larger spline. Being outside and a large board 2"x8", I was working on the premise of bigger = better. I'm still not convinced 3/4" depth is enough grip to last in the elements.

[John Lankers]

Use a handsaw if you don't have access to a RAS or don't want to use the router and clean out the slot with a chisel then cut a spline to fit. 10 minutes.

[Anthony Whitesell]

Let's recap.

Three options have been offered:

Half lap, standard miter, spline miter, and feather spline miter. I have concerns about trapping water between the two layers of the half lap and accelerating wood rot. The standard miter has it obvious problems. As for spline miter or the feather spline miter:

Use Tablesaw: Can jig a board 8+ feet long

Use RAS. Don't have one.

Use bandsaw: Table tilts wrong direction versus the direction the blade cuts

Use slotting bit. Maybe not deep enough to provide enough strength. (granted I don't know the required strength vs the strength of a 1/2" thick x 1 1/2" wide x 8" long spline)

Use hand saw: Cuts can be made, but the narrow chisels aren't long enough to clear the waste.


Any other corner joints viable that can be made on the end of 2" x 8" x 13' board?

[Jim Morgan]

I didn't say I didn't have one. I have a slotting bit that does 1/8" wide by 3/4" deep. The feather method andy mentioned would have a much larger spline. Being outside and a large board 2"x8", I was working on the premise of bigger = better. I'm still not convinced 3/4" depth is enough grip to last in the elements.

Diagonal on a nominal 2x8 is about 10.5". Allow .5" at each end to conceal the spline. 9.5" long x .75" wide ~ 7 sq. in. x 2 (for both sides of spline) ~ 14 sq. in. gluing surface on each side of the joint = a ton! 1/8" is a bit thin for the spline - 1/4" or 3"8 would be better. Prime the cut ends of the miter before cutting the slots - I'd be more worried about water getting into the end grain than the spline giving way.

[Anthony Whitesell]

Diagonal on a nominal 2x8 is about 10.5". Allow .5" at each end to conceal the spline. 9.5" long x .75" wide ~ 7 sq. in. x 2 (for both sides of spline) ~ 14 sq. in. gluing surface on each side of the joint = a ton! 1/8" is a bit thin for the spline - 1/4" or 3"8 would be better. Prime the cut ends of the miter before cutting the slots - I'd be more worried about water getting into the end grain than the spline giving way.

I am most concerned about water above the spline and between the mitered ends.

[Paul Girouard]

I am most concerned about water above the spline and between the mitered ends.


It's a exterior deck railing right? It's going to fail eventually . But with the spline , and sealing the end grain you'll have done as much as humanly possible. You could seal the end grain with CPES before you prime and after you cut the slots.

There's a point of practically and a time limit on all wood exterior jointry. Some place you have to find that balance.

[lowell holmes]

How about a bevel and band the joint with a copper or ss strap or, SS rod driven through the joint.

[Anthony Whitesell]

you could seal the end grain with cpes before you prime and after you cut the slots.

cpes? .

[Jacques Gagnon]

... in line with James's suggestion, you should be able to do the job with a router. You can build a jig (two sides on which the router will run) that will allow you to cut a groove to whatever depth you wish (limited by the length of the router bit) along the length of the mitre.

You will hold your board with clamps on the face of your bench and the surface of the mitre will be more or less horizontal.

[Phillip Mitchell]

How bout a dutch miter? Looks different and less material on the diagonal to shrink and open up as it dries.

I don't know if it was mentioned, but what material is your railing? PT lumber will most likely be soppy wet during install, and will a miter will open up within a few weeks even if it was cut and installed perfectly.

Having trouble attaching this pic, but here's the link from Google images...

http://freeplans.com/Resource.ashx?sn=n215MOW-Mitered-Rabbet

[Paul Girouard]

cpes? .

Clear Penetrating Epoxy Sealer :
Google : The Rot Doctor , in Seattle, Washington.








An Overview
Easy Instructions
Cure Time Chart
Coverage and Shelf-Life
Uses and Techniques:

For Restoring Rotted Wood
As a Primer
CPES Application
As a Sealant and Preservative






http://www.rotdoctor.com/img/prod/appguidesm.gif (http://www.rotdoctor.com/epoxy/AppGuide.pdf)


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CPES™
Clear Penetrating
Epoxy Sealer

An Overview
CPES is the leading product for treating rotted wood. Here's why: The fungus that causes dry rot retains a lot of moisture and resists the penetration of sealers and other rot treatments that cannot displace water. Also, the relatively high viscosity of most epoxy dry rot treatments prevents penetrating deep into the affected wood. In addition to alcohol, CPES™ contains other precisely measured organic solvents which act as "carriers" and take the epoxy deep into the wood and then evaporate out over a period of time. The resin is carried through the soft or bad wood and into the top layers of the solid wood to seal and form a bonding surface no other product on the market can achieve. The resins used in CPES™ are derived mostly from wood and when cured have a toughness and flexibility similar to the wood itself. To see test results of CPES™ and other epoxies marketed for wood restoration, go to our product test section (http://www.rotdoctor.com/test/penetration.html).
CPES is also an excellent primer. All wood contains moisture, as well as varying amounts of "sap". Different woods have different amounts of these which are chemically attached to the cellulose wood fibers. To obtain a good bond between the wood and a surface coating, the fibers on the surface of the wood must be strongly bonded to the coating. If not, the wood surface soaks up the liquid part of the coating and leaves the solids on top where deterioration is relatively rapid. CPES™ contains a high percentage of special solvents to displace and dissolve both the wood moisture and the sap and oils to form an enduring bond with the wood fibers.
Are there alternative ways you can treat bad wood using cheaper epoxy resins? The answer is no, not if you want to do it right. All standard epoxy resins (including WEST) are petroleum based. They cure hard and brittle. WEST and others suggest that you can thin their resins using such things as acetone, MEK, toluene, or alcohol for greater penetration. This is true, but are you a chemist to mix the right thinners in the right proportions to carry resin through bad wood and into good wood? And when whatever you put in there evaporates, you're still left with a hard resin. It's like putting rocks in your wood. Why bother? We've done it all for you with a tested, tough, flexible wood derived resin product. You mix it 1:1, stir vigorously, and apply. It's that simple.
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This stuff is very easy to use . . .
CPES™ is a two-component product with the consistency of diesel fuel, mixed 1:1, part A and part B. Apply by brush, solvent-resistant roller, sprayer, or inject by syringe until wood is completely saturated and will accept no more epoxy. Allow approximately 1-3 days for solvents to evaporate before applying paints, urethanes, varnishes, Fill-It™ Epoxy Filler or regular epoxy resin (see cure time chart below). Unmixed CPES, kept in closed cans and at above freezing temperatures, has a shelf life of over 5 years.
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[Bradley Gray]

Use the slotting bit you already have and make 3 or 4 passes to get to 3/8 or 1/2".

[Anthony Whitesell]

I opted for the spline miter joint. I couldn't find a slot cutting bit with a long enough shaft or a deep enough cut. The cut was from 1/2" to 1" from the router base and was to be 3/4" deep. I ended up using a 1/2" spiral upcut bit in a 2 1/4HP router with an edge guide (what a monstrous rig).

[Rich Engelhardt]

I'd never slot & join anything like that for a deck railing.
It's a deck - not fine furniture & it's in the nasty New England weather, not sunny Southern California.

I'd miter it with a handsaw or circular saw & use a mending plate on the underside leaving a small gap for water to drain away- and slop a ton of clear preservative on the cut miters.
Since it's all done, try to give us a shout about how it holds up.
I'd be curious.

[Anthony Whitesell]

Since it's all done, try to give us a shout about how it holds up.
I'd be curious.

Yeah me too. The miter ends were coated in epoxy, the splines epoxied in, and the gaps filled with epoxy. I'm curious as well. Luckily the wood cost me very little money, and a whole lot of time (jointing, planing, etc.)

[johnny means]

I'd never slot & join anything like that for a deck railing.
It's a deck - not fine furniture & it's in the nasty New England weather, not sunny Southern California.

I'd miter it with a handsaw or circular saw & use a mending plate on the underside leaving a small gap for water to drain away- and slop a ton of clear preservative on the cut miters.
Since it's all done, try to give us a shout about how it holds up.
I'd be curious.

Agreed. I'd rather my deck railing be easily repairable.