If you have substantial snowfall that stays all winter or frequent severe weather that includes high winds, then you’ll be looking at the rafter charts for 40 pounds per square foot. In this case, you’ll be looking at rafter span charts that estimate your roof load at 20 pounds per square foot. You may live in an area where your shed roof will experience very little disturbance – no snow, regular rainfall amounts, and occasional wind storms. means that your shed should be no wider – or longer depending on how you orientate your single sloped roof – than 11’. If you have a single sloped roof, then the 11’ span distance for 2×4 rafters O.C. Therefore, for gable roofed sheds, the rafter span table is indicating how far a rafter can span half of your shed’s width. If you have a gable roof on your shed, you’ll have two sets of rafters, with a ridge beam in the center uniting the rafters on each side. For instance, 2×4 SPF shed rafters can span up to 11’ when placed at 12” O.C. Understanding this is key to knowing how far your rafters can span. Another way to look at it is from the beginning of the birdsmouth cut to the opposite, interior facing edge. The span length is the measure taken from the inside of the shed framing to the interior apex of the rafter. If you forget to look at the store, don’t worry – the wood itself is usually marked SPF or SYP. There is a slight drop off in strength when using SPF for shed roof rafters, but in most areas, you only have one option when you go to your local home reno store, so at least know what you are buying. SPF is light and easier to use when framing. SYP is one of the densest softwoods, so it is strong but more difficult to cut and nail into. Many rafter span charts delineate between rafters using SYP (southern yellow pine) versus SPF (spruce, fir, pine) lumber. We will be looking at roofs that have a pitch of 3:12 or greater. While there are benefits to both, only rafters vary in the size of lumber that is used.įor more information about roof framing and how understanding the differences between types of shed roof construction, visit my guide to shed roof framing. Rafters simply rely on a center ridge beam and the outside walls for support. Trusses only use 2×4 lumber and are constructed using a “web” of 2x4s for strength. Lastly, remember that we are not talking about trusses in this article – just rafters. The reason for this is that flat or shallow roofs withstand much more abuse and loads than steeper roofs, making wider shed roof rafters a necessity. Many shingle manufacturers recommend no less than 2:12 when installing. Many roof material manufacturers have minimum pitch ratings for their products. 2×4 rafters are not strong enough for low pitched roofs under any circumstance, so avoid if you are building a shed with a flat or very shallow roof.

If you look at the chart linked above, you’ll notice that for roofs that are less than 3:12, the chart does not include 2x4s as an option. What does 3:12 mean? It means a roof that rises 3 inches for every 12 inches of horizontal run. When talking about framing a shed roof with rafters, you’ll first need to know how steep your roof is – in other words, what is the pitch or slope of your roof? Most rafter span charts are organized into 2 sections: roofs with a slope less than 3:12 and roofs greater than 3:12. Should I Use 2×4 or 2×6 Rafters for Shed Roof?.If you have a single sloped shed roof, then using 2×6 rafters is a better bet because the price differential won’t be huge and your shed roof will have a much greater load capacity.īelow we’ll take a closer look at when to use 2×4 and 2×6 lumber for your shed roof, and hopefully, you’ll be able to make a more informed decision on what type of lumber you should use when building your shed roof rafters. If you have a simple gable shed roof, then using 2×4 rafters makes more sense unless you have a very large shed. For roofs that will experience heavy snow or wind and will span the same distance, use 2×6 rafters. For roofs that won’t experience heavy snow loads, a gable roof can span up to 22’ with 2×4 rafters. You can use either 2×6 or 2×4 rafters for roofs with a 3/12 pitch or greater, but it depends on the overall size of your shed. However, one of the main issues you will encounter when cutting rafters is, should you use 2×4 or 2×6 rafters for your shed roof? They require less lumber than trusses and once one is cut, all the others follow the same cut.

Rafters are a simple, straightforward way to frame the roof of your shed.

Shed roof rafter span calculator