Securing steps to deck

[notbob]

I got my pressure treated stringer boards, today. I had no idea they would be so heavy. I bought 16 footers, cut in half for easy transport. Damn, I must be getting old. The finished stringers will be no more than 48" in length. In light of the increased weight of the stringers, I'm even more concerned on the method of mounting the steps to the deck. I've noticed several methods, of which I'll try to relate.

One is this obvious method of a right angle bracket. I assume there is one on each side of the stringer, staggered, of course (yes/no?):

is notching the stringer to rest on top of a "ledger", as shown in Fig N: method on my old deck is a lazy variation of the above ledger method, only the stringer is not notched to rest ON the ledger. The ledger is cut to fit between the stringers and the stringers are secured by 3" deck screws run through the stringer into the ends of the inside ledger.

My lumber man offered another method usng long 2" wide galvanized straps. I thought he said the straps were secured to the deck and hung down and secured to the back and underside of the stringer, using short strap nails. I'm still vague on this method. Maybe someone can elaborate.

Again, considering the surprising weight of the PT stringers, along with the aged wood of the old deck, I am looking for most secure method of mounting these monster steps. I'm thinking the right angle brackets along with the notched stringer ON the ledger might be more than enough support.

Also, the lumber guy commented on how deck screws are brittle and tend to break in any application other than downward. When removing the old treads, I noticed several deck screw heads had rusted through and just spun in their holes. In fact this old deck is assembled soley with 3" deck screws and a handfull of lag bolts on stress-bearing joints. I guess this is why the lumber guy recommended short fat strap nails. Being an old pre-nailgun 16 box n' hammer man, I'm kinda enamored with this newer kinder (I'm in no hurry) screw gun technology. Since I've got a hot new screw gun, what might be more appropriate fastener for secureing the vert surfaces in this application?

Any and all advice will be much apreciated. Thank you.

nb

[Morris Dovey]

have some concern about what happens with freeze/thaw heaving of the ground the stringers rest on with the other methods...

I'm not a carpenter or builder so you got from me pretty much what you paid for. :)

[Limp Arbor]

Go to page 14 of this pdf.

usually get attached with short fat galvanized nails. Once you fill every hole with a nail, those stringers aren't going anywhere. Should be available at almost any lumber yard, either Lowes or HD doesn't sell Simpson but the other does.

Forget the ledger method. Look at the stringer, once you account for the notch for the risers and treads and the notch for the ledger you are effectively building your stairs on a 2x4.

[Doug Miller]

Don't worry about the weight -- they're heavy because they're soaking wet. Once they dry out, they'll be much lighter. Lumber is pressure-treated with a water-borne preservative solution forced deep into the wood under high pressure. It takes a *long* time for all that water to evaporate.

[Chris Friesen]

Screws are available in varying quality. Better ones are not brittle.

For shear loads you want to size them such that the shank of the screw is the same size as the nail you would have used.

Chris

[Chris Friesen]

Is this actually problem, given that it's only at one end of the stairs? It takes a fair bit of force to shear off a 2x4, and you'd still have the full width for the rest of the stairway to provide stiffness.

Chris

[Jimbo]

Poor quality pressure-treated lumber is soaking wet. Quality lumber is kiln dried, treated in a pressure chamber and then dried again.

[RicodJour]

The 2x4 is obviously strong enough to carry the stair load. Most stringers end up with only a few inches of "beam".

The OP shouldn't be worried about the dead load of the steps. The live load is much more critical.

A ledger doesn't have to be a 2x4 - a 2x3 or even 2x2 will work. If you want to do a belt and suspenders, and you don't mind the exposed metal, omit the ledger and use joist hangers. A joist hanger can carry one half of the load of a full length floor joist, so it will certainly carry any load you can put on those steps.

R

[Limp Arbor]

A chain is only as strong as it's weakest link and a board is only as strong as it's thickest point.

In reality probably not a problem but why do it when there are simple brackets available that will do a better job.

[Kerry Montgomery]

A chain is only as strong as it's weakest link and a board is only as strong as it's thickest point.

In reality probably not a problem but why do it when there are simple brackets available that will do a better job.

Limp Arbor, I suspect you meant "thinnest", yes? Kerry

[dpb]

Limp Arbor wrote: ...

No. Even though the notch in that figure in order to match top of stringer to proper height is larger than the minimum possible by using a

2x4 ledger (instead of 2x3 or 2x2), the pertinent dimension for the width of bearing on the stringer is the distance from the notch corner _PERPENDICULAR_ to the length of the stringer, not the vertical distance. That distance isn't significantly less than the depth of the stringer at the notches so there isn't any less strength at the end than in the middle.

--

[Chris Friesen]

I'm assuming you meant thinnest here. In any case, this isn't the whole picture, because the forces on the board are not uniform. Because of this, it makes a big difference where the thin point is.

If the thin point is in the middle, it will reduce the stiffness and strength greatly due to the decreased moment of inertia at the point of greatest stress. If the thin point is at either end it will have little impact on the stiffness and the decreased shear strength is not going to matter in this application.

This same principle is why you're not supposed to notch solid floor joists in the middle third of the span.

Chris

[dpb]

Chris Friesen wrote: ...

...

You're right about effects but mixing comparisons between the strength of the material and the loading effects of bending moment, etc.

As noted above also in the particular case the actual relevant dimension isn't the vertical distance above the ledger but the width across the span normal to the length which is almost equivalent to the minimum depth at the riser notch.

--

[PDQ]

And, if you are going to use screws, use _stainless_ as other coated = and dipped nails and screws will do exactly what the old screws on your = deck did - rust off. =20

P D Q

[Limp Arbor]

Maybe you guys are right but I was looking at it like this (use fixed font to view) The dotted lined represents the *thinnest* part of the stringer so it would only be as strong as a 2x4. (kind of tough to draw)

/\ /\ /\ / \ / \ / \ / \/ \/ / \ ..................... / \/\ ________________/ notch for ledger

Of course it is never caryying a load at this angle so I am sure it isn't as simple as I think and I've seen lots of stairs made this way so it is probably fine. However I came across something that I never heard before and would like see what the group thinks.

paragraph on page 182 states: "Ripping wide dimension lumber lowers the grade of the material and is unacceptable under all building codes"

If this is true why is it true?

Is it because of the location of possible defects like knots? If not for the notty knots why can't I rip a 2x12 down to a 2x10 and use it?

[RicodJour]

I'd never heard of that rule, but I'm sure the location of knots has everything to do with it. If it is a rule, it's a bit stupid. You're only going to be ripping one side, so put the ripped side on the compression side and it's no longer a concern.

R

[Nova]

or

I only read the paragraph you cited but my guess is they are saying you can't rip a floor joist where the final dimension would be less than that as engineered and specified on the building plan

[Martin H. Eastburn]

When we lived in the redwood mountains out west - our deck was 30+ feet high. The stairs were on brackets like this. We had 4 landings on the way down several were nice outlooks. One between several tall trees.

Typically they were nailed - special short nails that are really tough. Then a lag bolt or two on each side.

Allow for expansion and shrinkage. Water expands wood and sun shrinks. Wet wood shrinks. Doubt if you use kiln dry deck wood.

Martin

Morris Dovey wrote:

[Tom Veatch]

Not sure I can agree with that assessment. Your suggestion would surely work in specific cases, but I'm sure you'll agree that a board with a defect/knot in one edge should not carry the same grade as one with a small, tight knot centered in the board. Grades also specify a maximum ratio of defect width to board width.

Ripping the board could easily place the defect too close to an edge and/or increase the width ratio above the maximum for the grade. The rule invalidating the construction grade when the board is ripped is, IMO, a good rule.

Tom Veatch Wichita, KS USA