Mortise and Tenon for Deck Rail?

[hannah01]

I need to make a railing for a brick/concrete patio and steps. I wanted to make it with P/T lumber using mortise and tenon joinery for the ballusters, rails and posts.

The posts will be anchored to and/or set in concrete. I would like to use waterproof wood glue without any metal fasteners. Has anyone done this and is the strength sufficient for a railing.:eusa_thin

Anyone knowledgable with applicable building codes, please chime in.

Opinions, comments, suggestions, helpful reading are appreciated.

Thanks.

 

[Ray Martin]

Joe,

I think metal fasteners are required. If the wood is pressure treated, the fasteners should be hot dip galvanized. If the wood will be in contact with concrete, metal flashing is appropriate as the concrete is caustic. Flashing should also be galvanized.

As to required strength... the railing has to withstand 200 pounds of lateral force.

Mortise and tenon is terrific joinery... it looks great... there is a challenge here though. Pressure treated lumber will shrink in the first 3 to 6 months. All the precision put into the joinery would be lost as the wood dries and shrinks. Rain and sun will exacerbate this over time.

Posts can be anchored from the ends, making the hardware almost invisible. Galvanized feet can be attached to the conctere with something like a Red Head (anchor). You could hide this foot and associated screws with "base molding" cut and milled from a 5/4 deck board.

If you attach a photo of the deck or patio, we might be able to offer some other ideas. There are also some code requirements with regard to spacing, height, etc. Let me know if you want to chat about them as well.

Ray

 

[hannah01]

Thanks Ray.

Yes, I have stainless steel fasteners available, so I guess I will use them and forget the M&T joinery. I know the ballusters must be spaced no greater than 4", but what are the height requirements? I'm sure I will be well above them, but just in case...

I will be using the galvanized brackets that are attached to the concrete and the post fits into them with some trim around to hide them.

Where it will be attached to the side of the brick, I was planning on using some washers as spacers to allow a thin gap between the post and the brick/concrete to allow for moisture to dry. Is the flashing still required?

One more thing, when anchoring into brick and concrete for this type of construction, is it appropriate to anchor into the mortar or should they be in the brick itself?

Thanks again.

 

[McRabbet]

Joe,

Steve D (DeWeese) and I recently completed a large deck project where we used Mortises to secure the horizontal railing members into 4 x 4 posts. Three 2 x 4 PT rails (a horizontal cap at 36" above deck level and vertical rails "teed" below the cap rail and at 2" above the decking) were set into 1" deep mortises in the posts. We used powder-coated architectural balusters on 4" centers screwed into the 2 vertical rails and secured the posts with counterbored 3/8"x 4" lag screws into the fascia. To secure the rails further, we blind toe-screwed through the rails into the posts from the outside, under the rails to keep the fasteners invisible. See the thread http://www.ncwoodworker.net/forums/woodworking/general.woodworking/3465-deck.project.html and Steve D's Photo Album (Coddington Deck) for more details on the job. Feel free to send any questions our way.

Rob

 

[Ray Martin]

Thanks Ray.

Yes, I have stainless steel fasteners available, so I guess I will use them and forget the M&T joinery. I know the ballusters must be spaced no greater than 4", but what are the height requirements? I'm sure I will be well above them, but just in case...

I will be using the galvanized brackets that are attached to the concrete and the post fits into them with some trim around to hide them.

Where it will be attached to the side of the brick, I was planning on using some washers as spacers to allow a thin gap between the post and the brick/concrete to allow for moisture to dry. Is the flashing still required?

One more thing, when anchoring into brick and concrete for this type of construction, is it appropriate to anchor into the mortar or should they be in the brick itself?

Thanks again.

Height of handrails: On stairs with 3 or more risers, measure from the front of the nosing of the stair tread to the top of the handrail. The top of the handrail must be between 34 and 38 inches striaght up. If you have a handrail next to a wall, the handrail must be 1.5" from the wall.

On the porch, if the porch is 30 or more inches above grade, you must have a railing. The railing must be at least 36 inches high, measured from the patio or deck surface to the top of the handrail. The triangle formed by the bottom rail of the balustrade, the riser of the step, and the tread of the step must be small enough to prevent a 6" sphere from passing through.

On baluster spacing: I use a scrap of 2 X 4 as a spacer. That keeps you under the 4" max. the bottom rail of the balustrade must also be less than 4" above the surface of the deck or patio. If you start placing balusters in the middle, you'll end up with equal spacing at the ends.

On spacers: If you have a space between the wood and the brick or mortar, you do not need the flashing. Make sure you use large washers, like fneder washers, so you have a strong connection.

By the by... are you building steps too? or is it just the railings?

Hope this helps. Feel free to send more.

Ray

 

[hannah01]

Ray, thanks for the detailed info. Here is a picture of the stoop/porch that I forgot I had...

One side has a small deck built next to it and the other side is completely open. The picture is oriented so that you are standing on the stoop with your back to the door into the house. On the left is a deck and the right is nothing but a substantial drop--hence the railing. :lol: The stoop measures about 5' square.

The top of the stoop butts up against the deck, however there is a 12" or so gap between the steps and the side of the deck. In other words the steps are narrower than the top of the stoop. Will both sides of the stoop need a railing, or just the right-hand side opposite the deck?

I was planning on having three posts, one anchored to the top of the stoop and to the side of the house (post #1), one set in concrete that will run down the side of the steps against the brick stoop (post#2) and one set in concrete at the bottom of the steps (#3). Do you think it's necessary to set post#2 in concrete or should I just attach it to the brick patio?

Thanks for the info on measurements. I didn't know the size requirement for the triangle of the railing, tread and riser. :eusa_thin

 

[hannah01]

Thanks, Rob. I do remember seeing that thread a while back. beautiful work and some good ideas, too. :icon_thum

 

[Ozzie-x]

Decks are a lot of fun. Ray did a good job of citing some of the code and architectural points for decks. Couple tidbits: they changed the chemical formula used on pressure treated lumber a couple of years ago to get rid of the arsenic. The "new" chemicals are very corrosive and the galvanized and stainless steel fasteners (we previously used) will corrode away within a years time in the "new" TP and fail. The "new" recommended "correct" fasteners are the coated type fasteners rated for use with the new chemical preservative. The new screws are (of course) more expensive, but they're a lot better screws, at least the ones I've had. It's hard to believe, but I don't think I've ever wrung one off and I shot maybe 40 lbs of them in our new deck.

The synthetic trex deck material is expensive, but is very suitable for spacers and other uses where wood is not appropriate. Trex makes great spacers for the rail and header connections to the house. You can't pay too much attention to drainage, connections, etc and considering constructing the deck so tht the water drains out of the wood and the water doesn't collect or pool.

 

[McRabbet]

I agree with Ozzie-x on using the correct fasteners with the new ACQ PT chemical -- we put a plastic washer under each baluster screw (4 per unit) to prevent contact corrosion. And we drove nearly 40# of #8 x 2-1/2" screws without a single one breaking off. Also agree with the 2x4 spacer for balusters -- we used a "story board" to insure equal spacing across the post-to-post span.

Looking at the picture of the stoop, I believe you will need a railing down each side of the steps to meet code.

Rob

 

[walnutjerry]

. I wanted to make it with P/T lumber using mortise and tenon joinery for the ballusters, rails and posts.

Has anyone done this and is the strength sufficient for a railing.:eusa_thin

.

Opinions, comments, suggestions, helpful reading are appreciated.

Thanks.

I have done what you are talking about------I installed sections of picket railing (shop built from oak) to red cedar posts by mortising the posts and inserting a "tenon" that projected from the post about 3 inches. I used wood pegs in both the post and the upper "apron" (a 1x4 on either side of the pickets just under the cap of the rail) to fasten it in place. That was probably 20 years ago----It is still in place.

My porch was entirely wood construction so I did not deal with the fastening to masonary. But as an ex-bricklayer-------it is easier to drill the mortar usually but when joints get loaded with water and freeze the mortar begins breaking down.

Jerry

 

[Mark Anderson]

just two things to add.

the code o pickets says "a four inch sphear can not pass through" not 4'' max. the way pt lumber will warp and twist if you space pickets 4'' apart you are just asking for trouble. 3-7/8 is as far as i would dare to go.

there is a relatively new code (2 yrs old i think) that you can not use aluminum flashing in contact with masonary, no one i have talke to can tell me why other than the aluminum will react to the masonary....20 years in the trade pulling apart houses made long ago i have never seen it. but who am i to argue with the dept of insurance.

 

[Ray Martin]

Joe,

Amazing just how much goes into stairs and railings... that's why, back in the bad ol' days, building a set of stairs was one of the tests to move you from apprentice to journyman.

The code says that a railing "... shall be provided on at least one side of stairways." BUT... unless the stairs are within a few inches of the house or side of the deck, railings on both sides would be safer, and better looking.

One trick to getting the height of the handrail correct and at the same height from all steps... if you are planning on putting the handrail on top of the post, place the post in the same place at each step. In other words, if you have a post at the front of the step at the bottom step, then put the post on the top step at the front too. If you plan to attach the railing to the side of the top post, this isn't a concern. I've seen a lot of handrails installed with a different measurement from tread nosing to rail at every step. This is almost always caused by placement of the post at the back of the top step and the nose of the bottom step.

With regard to Ozzie-x's comment about fasteners... while they are a bit more expensive than the hot-dipped galvanized, the poly-coated screws he recommended should be impervious to everything short of nuclear radiation... and they come in a light brown that makes them blend in with the pressure treated lumber. The Deck Mate brand screws are also self tapping (although you might drill pilot holes at the ends of boards anyway).

Ray

 

[hannah01]

Hey, thanks everyone for the info. Especially Ray who has been very patient in answering my novice questions. :icon_thum

Is that right, stainless steel is no longer a good choice with PT lumber? I thought it was still a step above the coated ones as far as strength and corrosion resistance? The "International Building Code, International Residential Code and International Code Council Evaluation Services recommend hot-dipped galvanized fasteners or stainless steel fasteners for pressure-treated lumber"

http://www.popularmechanics.com/home_improvement/smart_consumer/1275056.html

Is this not correct? Help me out here--conflicting info always makes me worry... :-? Not to mention that I have recently stocked up on some stainless screws and bolts for outside projects. Not cheap!

 

[McRabbet]

In my experience, hot dipped galvanized fasteners will outlast the wood. Stainless steel is good, but there are so many grades of it that I would not venture to say it would last as long as the new coatings. Unfortunatley, there is no historical data on the new screws or the new preservatives.

Rob

 

[hannah01]

Ok, I'm using "Passivated type 305 stainless steel" which is a step up from the normal 304. According to all the literature I can find, SS is fine if not ideal for PT wood.

 

[Ray Martin]

Hey, thanks everyone for the info. Especially Ray who has been very patient in answering my novice questions. :icon_thum

Is that right, stainless steel is no longer a good choice with PT lumber? I thought it was still a step above the coated ones as far as strength and corrosion resistance? The "International Building Code, International Residential Code and International Code Council Evaluation Services recommend hot-dipped galvanized fasteners or stainless steel fasteners for pressure-treated lumber"

http://www.popularmechanics.com/home_improvement/smart_consumer/1275056.html

Is this not correct? Help me out here--conflicting info always makes me worry... :-? Not to mention that I have recently stocked up on some stainless screws and bolts for outside projects. Not cheap!

The International Residential Code, which is a model code, can be adopted, or modified or rejected (and replaced with one of their own) by state and local governments. It's updated every 3 years. The last update came out in January.

The newest versions of pressure treated lumber will supposedly eat anything less than hot dipped galvanized or poly coated fasteners. The old CCA type (chromated copper arsenate) presure treating was tough on fasteners... the new stuff (alkaline copper quat (ACQ types B and D) and copper azole (CBA-A, CA-B)) is worse... but supposedly more evironmentally friendly. The new goop used to pressure treat lumber has much more copper and is therefore more corrosive to the fasteners. I have seen the remnents of regular steel nails and screws that were in pressure treated stuff for a while... in some cases ther was nothing left but a stain. ( I have a couple of neighbors who are chemists... I'll have to ask them what the story is.)

There was note about aluminum flashing somewhere in this thread. Galvanized flashing is now the only acceptable metal material since high concentrations of copper are supposed to be very corrosive to the aluminum.

Ray

 

[Gofor]

Two observations:
1. Aluminum flashing: First, aluminum is anodic to copper (the aluminum will corrode away quickly to "protect" the copper. Second, aluminum does not like alkaline environment, which will destroy it (starts by turning it black). Masonry is alkaline by nature, so will attack it. Anodized and good protective coatings work until the coating is scratched thru, etc. Galvanized is zinc-coated steel. The zinc is designed to be sacrificial to protect the steel, and it self passivates. It is succeptible to acid attack, but the alkaline nature of mortar/concrete actually helps to slow the acid attack of the environment.
2. The most common corrosive substance to attack "stainless" steel is chlorides. Sodium chloride is the most prevalent, and 304 & 305 stainless are good at resisting it (not impervious). That's why most commercial fasteners are 304 or 305, because a lot of people use them for marine (saltwater exposure) environments. 316 which has higher molybdenum is better but is more expensive (Don't try to boil Langusta tails in sea water in a 304 SS pot though, 'cause it will corrode holes in it. High temp really changes the process. DAMHIKT!)
I built a handicapped ramp last October using the stainless for all below grade attachments and major substructure and the green Phillips "Deck-mate" screws for the cross boards, railings, etc. Two weeks ago,I had to dismantle it and drop it down several inches because of some landscaping changes. All the fasteners still looked like brand new (both the stainless and the green screws.) Before I moved here, I built a ramp for my storage shed from PT lumber and used the galvanized "Grip-Rite" fasteners. I will never use them again. Even with predrilling, they would bend or snap if they hit a resinous knot, and after three months, snapped off when trying to remove them. The embedded pieces, which I removed with vise-grips, were corroded. The heavy galvanized lag bolts were in good shape tho.
IMHO: the SS fasteners will outlive the wood also.
My experience:lol: