![]() ![]() The strips provide an even, level base for the metal panels. ![]() It’s not a good idea to try to install metal roofing over shingles without the strips. Can You Put Metal Roofing Directly on Shingles Without Furring Strips? Check out my article What’s the Best Metal Roofing for a Shed? if you need more information on the types of metal roofing. More people are using 2 x 4s these days for a sturdier attachment. However, due to the way wood is milled, boards are usually a bit smaller in width than stated, for instance, a board labeled as one inch wide is much closer to 3/4 inch thick, which doesn’t meet the screw manufacturers’ guidelines. Most strapping has traditionally consisted of 1 x 4s. Even the manufacturers of some roofing screws state that their product has to be attached to at least one inch of solid wood, which leaves out most plywood. They tend to work their way out of the plywood during the normal expansion and contraction of the metals and the force this exerts on the connections. Plywood just will not hold the roofing screws for long. If you have plywood roof sheathing, which is very common, it’s almost a given that you will need furring strips. One good reason for strapping is to ensure that the panels are firmly attached and will stay that way. This allows for further ventilation or installing insulation between the vertical strips before nailing the horizontal strips over them. Some people like to install vertical strips first, then the horizontal ones across the roof for attaching the metal panels. The manufacturer of your roofing should have recommendations on this.įor instance, standing seam metal roofs require furring strips or battens. Some say they never use furring strips some say it’s only necessary when installing a metal roof over existing shingle roofing, others say metal roofs should always have furring strips. This is an ongoing argument among roofers and do-it-yourselfers alike. If your in a hurry, and want more help with your roof check out my recommended shed plans “ Ryan’s Shed Plans” and get started today! Do You Need to Put Strapping Under Metal Roofing? ![]() Installing roof strapping is simply attaching either 1x4s or 2x4s to the roof rafters and then you attach the metal roofing to the strapping. It also provides some space between the roofing and the underlayment, providing additional insulation, airflow to prevent moisture problems, and some sound deadening. The strips, also referred to as furring strips, nail strips, purlins or battens, provide a smoother surface when installing a metal roof over an existing roofing material, such as shingles. The nails/screws attach to these strapping strips. But I'm not aware of a prescriptive table that covers the combination of some 2x purlins plus thinner OSB sheathing.Roof strapping refers to wooden strips to which the metal roofing material is attached. Spanning between the rafters is a separate check, and the info so far in this thread has been that 2x T&G decking can span 48", or that sufficiently thick plywood or OSB could work. If the snow load is higher, then you'd need to check something like the WFCM to see if it has an applicable span table, with or with out the load doubling trick. should span 10' (and be stiffer than typically required, as the deflection limit is L/360, not the L/240 or L/180 of the rafter span tables). So the 2x10 rafters with 10 psf dead, 20 psf live, and 48" o.c. If you halve the loading and double the spacing, the load per member is identical. If the dead load is 10 psf or less, and the snow load is 20 psf or less, then IRC Table R502.3.1(2) tells you than any of the species in #2 or better can span over 10' with 20 psf dead, 40 psf live, 24" o.c. Click to expand.On the rafters, what is the dead load and what is the snow load? ![]()
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