This sizing guide for roof rafters will help determine what you need for your small project.
Lumber roof size in cm.
Last updated july 15 2018.
What size lumber would i use to span 20 ft.
Well when the lumber is first cut from the log the piece after that rough cut has the approximate width and depth the nominal dimensions by which the piece will be referred to from.
Outside of the u s a degree angle is typically used.
Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter.
X 2 rafter length 4 5 2 3 5 2.
In modern lumber practices the boards are no longer exactly 2 x 4 inches when first cut but today s drying and planing methods still leave the board.
If you have multiple planks of wood lying end to end then the calculator can also work out.
These sizes are as follows.
You can give measurements in imperial units inches feet yards or metric units centimeters meters.
Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope.
On a shed roof 2 12 slope metal roofing material.
For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches.
There are several variables to consider when determining the proper rafter size.
Is it ok to space rafters on 4 and use 2x4 on their edge on 2 centers as is done in pole barns.
Board foot calculator roof pitch calculator tile calculator paver calculator.
Just enter the dimensions of the roof rise and run to get started.
With the diagram above applying pythagoras theorem.
Roof pitch is a determining factor for cost of the roof as well as the roof area and the type of materials used.
I am wanting to build a 20x30 shed roof on the end of my existing 30x50 work shop for rv storage as cheaply as possible.
Nominal actual surfaced size dry size 2 x 4 1 1 2 x 3 1 2 2 x 6 1 1 2 x 5 1 2 2 x 8 1 1 2 x 7 1 4 2 x 10 1 1 2 x 9 1 4 2 x 12 1 1 2 x 11 1 4 4.
Originally a 2 x 4 was cut as a rough green board that was exactly 2 x 4 inches in size but by the time the boards were dried and planed the boards became smaller approaching the now standard 2 x 4 dimensions of 1 1 2 x 3 1 2 inches in size.
Lumber sizes tabulated spans apply to surfaced s4s lumber having dimensions which conform to the american softwood lumber standard ps 20 05.
For rafter check the height of roof and the breadth of plan to determine the rafter which is the falling portion of the roof except is already given from the section lets take the height of the roof as 3 5m and the breadth of plan plus overhang is 9m.
If you re building rafters and aren t sure where to start when determining the length of your lumber you re in the right place our rafter stock size calculator shows you how long your rafters should be so you ll know what you need in terms of framing lumber dimensional lumber studs and more.
