On Jul 15, 6:52 pm, Weatherlawyer wrote:
On Jul 15, 2:10 pm, "Arthur2" wrote:

Trav Perks have

SAWN DRY GRADED C16 TREATED 47mm x 250mm (841536)

Is this the right stuff for a stair stringer?

I know that T & P have a timber mill quite near here and they might plane it
for me.

What are you doing making stairs when you don't know anything about
grading timber?

No offence but if it is going outdoors or something, that's a
different question. It's just that you don't seem au fait with either
joinery or newsgroups. Which is it?

That sounded very condescending but it really was a brash OP. Here is
a site that deals with grading timber:

http://www.tda.org.uk/NetBuildPro/pr...ewsview13.html

3. Timber grade (Strength Class): C16 minimum

The grade (strength class) of timber used for structural components
such as posts, beams and joists shall be sufficient to cope with the
loads placed upon it during its service life. Softwood with a strength
class rating of C16 is considered the minimum standard.

For decks below 600mm in height the use of C16 timber is recommended.
For structures over 600mm the use of strength graded timber is
essential and required by Building Regulations.

The higher strength classes, typically C18 and C24 should be
specified where smaller component sections, longer spans or commercial
deck performance design considerations are required.

Note: Do not exceed the recommended load and span for each strength
class - refer to span tables in the TDA Timber Decking Manual for
detailed recommendations.

*********

Sawn timber will lose some 1/8" per face planed. More if a warp or
bend has to be removed. However, a staircase is an enormously strong
structure if glue is used in the housings. So good that if you just
took off all the doors in your house and put them in front of you in a
stairwell instead of getting laid when the 3 minute warning siren rang
in the Cold War...