I am in process of replacing complete set of outside steps. The tread are 48" long and will have seven.  Do I need a center support. I have two already sawed out, and I don't think I need a center one. They are 2"x12" and are about 7' long.  If I need to, I could nail vertical supports in place instead of third support. 

d

Three stringers would be good. 

for the first year or so, you wouldn't see much droop, but over time the 48" span would sag.  why take a chance?

Please check your local inspector or standards.

3 is the requirement >36" around here.

 

One extra cost next to nothing compared to having to go back later and do it over..

I used three, although I do not believe it would have made any difference. Why take a chance!

I believe code in my area would require qty 4 for 2x tread material.  If you are using composite matl for the treads you will have to consult the mfg.  Some matl require spans to be 12" or less for stairs.   Danl

44 minutes ago, Danl said:

I believe code in my area would require qty 4 for 2x tread material.  If you are using composite matl for the treads you will have to consult the mfg.  Some matl require spans to be 12" or less for stairs.   Danl

With a 48" span, four would be over kill, I'd think. 

Stair stringers should be 16" on center just like the deck floor.  Three stringers would be fine for 36" wide stairs.  Hear is a link to decks.com

 

https://www.decks.com/how-to/69/deck-stair-stringer-layout

 

This means you will need to install a minimum of four stringers on any stairway wider than 36”. Always check the maximum span for your decking material as it applies to stair treads. 

 

 

Edited June 13, 20196 yr by HandyDan

Our deck stair treads are 48" wide, each made of two 2x6 redwood decking boards, for a 12" deep tread.  We used 3 stringers and, it's worked well for 11 years. Passed inspection, too. Though, our codes my not be as stringent as some. 

Definitely go with three . Not a lot of extra work and you'll be glad you did.

11 hours ago, Gene Howe said:

With a 48" span, four would be over kill, I'd think. 

Okay I admit it, I would do 4..... 

36" wide

Too wide a span makes for "bouncy" steps....that start to work fasteners loose. 

4 minutes ago, steven newman said:

Too wide a span makes for "bouncy" steps....that start to work fasteners loose.

Make it out of concrete no more bouncy stairs.  

BTDT....@ $28/hour......

 

One of the first jobs on a new jobsite...was to build the steps and a deck  for the job trailer/office....sometimes even had to build the steps out of the tool trailer, too.

56 minutes ago, steven newman said:

.sometimes even had to build the steps out of the tool trailer, too.

I need a sloped entrance to my deck.  Rise is about 2 1/2 inches over 4 feet.

9 hours ago, Woodbutcherbynight said:

I need a sloped entrance to my deck.  Rise is about 2 1/2 inches over 4 feet.

Itsy bitsy risers?

8 hours ago, Gene Howe said:

Itsy bitsy risers?

Called a "RAMP",   actually...