Flashing Under Shingles- Entire Roof

Not a professional roofer here-- but it would seem to me that once you drive the shingle nail through it, it's just extra weight on the roof...

That was my first thought. If I want a durable shed roof and was willing to pay the expense, I'd go to the roll-form roofing dealer, and get panels the right length, and the proper clips and fasteners to tie it all down with no penetrations through the metal facing the rainy sky. If you can live with slightly 'off' colors, you can get the stuff amazingly cheap. PITA to put up without helpers, and make sure everyone has leather gloves, but quite durable.

There is no point. Flashing is to keep water from coming in seams and edges, and wicking up from the bottom. It'll do nothing in the middle. If you are really anal, use "Ice and Water Shield". This stuff is a heavy rubbery sort of rolled roofing that sticks to the deck and seals the nail holes. It's commonly used to seal the bottom 4' of a roof deck against ice dams. The stuff is expensive, but will be a lot cheaper than flashing, which will do nothing.

That's a *long* time.

No negatives, just no point to it. If you're willing to pay for that, just put on a metal roof. It's likely to be cheaper in the end, and it will outlast all shingles. It's not that hard to install either on a small and low shed without a lot of gables and stuff. All you need is the metal, neoprene screws, a power drill with 1/4" hex tip, and a tin snips. Smaller sheets of steel are lighter than shingles too.

bithane rather than tar paper. it sticks to the wood and all nail holes are self sealing

its expensive but worth it espically if your covering chipboard, which disengrates if it gets wet

Use Ice and Water Shield, it will fill in around all the holes from the shingles, aluminum will not do that.

Using chipboard on a roof is just plain stupid. Eventually all roofs will leak, especially shingles. By the time the leak is noticed the chipboard is usually ruined. So instead of applying some tar or a couple new shingles, you end up ripping the whole roof apart. Not only that, but shingle nails dont hold well in the stuff.

Personally I dont think much about chipboard for ANY buildings. Water gets to it and its shot. Its fine for cheap cabinets and furniture, but not for roofs or floors. When I was in the repair business, I was constantly replacing large sections of floor in mobile homes because most of them use that crap for the floor. I put my leg thru more than one of those floors. Usually by doors or in bathrooms. I'd patch them with 3/4" plywood, and cover the whole floor with 1/2" plywood.

Now, what is bithane? I never heard of it.

Metal flashing under nailed down shingles would be an absolute waste of time and money. If you would like, you might consider a full layer of ice shield under the shingles or a standing seam metal roof. Here is some information about ice and water shield:

If you are going for the brick shithouse effect, you should be looking at seamed steel or copper, and not shingles at all. Or perhaps slate, if you can even find it.

nate

Oohhh, copper, pretty. Thieves like it too.

Shingles are a simple job. Standing seam steel, not so much.

Thanks to all for your thoughts. I will probably use conventional felt paper, but am looking into fire and ice. Frank