Steel roof valley cuts--won't they rust?

I’m considering a steel roof for a current new house construction project. However, there are six valleys on the house. Won’t the steel rust where we cut it to fit the valleys?

Would aluminum be a better choice? Any recommendations for steel/aluminum manufacturers or subcontractors?



You can use a hook strip in the valley. Add an extra inch to your valley cuts and use benders to bend the extra into a hem. Use the hem to lock into the hook strip. We usually have a 6" exposure on each side of the valley to help alleviate the snow build up and let the water run freely.


We pretty much do it the same way as roofboy described. I’ve seen some roofs where panel is cut at an angle and screwed right down to the valley. I mean this method will work for some time or on some barn, but we would never do that.

We still prefer aluminum over steel, as there is 0% chance that alum will rust. This is not to say that steel is not good enough. I have some pieces of g-90 steel just laying on the ground in mud, under rain/snow, and no signs of rust so far…

Any recs for aluminum manufacturers–probably standing seam?

I figure if I start with a good product company, they can refer me to a good contractor.

Thanks again,


MFG: Firestone Building Products, Englert…

Here is a metal roofing directory of both manufacturers and contractors:

Good Luck

the main thing is not to heat up the edge your cutting
it will accelerate the rust process.
use tin snips to make your cuts.
use a galvalume coated steel panel and paint that, or leave it mill finish.

regular home depot metal will rust in a couple a years.


i just did a roof with coated steel valleys,and i find it cleaner to snap a line,mark top and bottom,make your cut then install your shingle.a little slower,but a much cleaner job.

May rust where it is cut or bent because it mars the finish coat. They can use touch up paint that comes with the metal.