Hurricane Andrew & Gustav has convinced me to put a metal roof.
I'm too old to keep patching shingles.

I'm undecided :

on using treated 1 x 4 lats directly over shingles (parallel to ridge), screwed to rafters
and metal screwed to lats

or

using one of these new synthetic roof underlayments I've been reading about, such as
Tri Flex 30, Titanium UDL, Roofsheild, etc... installing directly over shingles, then screwing metal to rafters (hitting rafters harder this way)

Any advice/info greatly appreciated.

you can put the metal right on the shingles,this is cost effective. Using the 1 x 4 perlins makes it easier for screw location and you can use shorter screws.

Dannac - First of all I would use what we call bubble wrap on the shingles then put down the 1x4sI think that the location you are in though I would go with spaceing them on no more then 16" centers ,instead of 24" centers for more strengh. The bubble wrap is for insulation. If you get the first 2 rafters right then you should be able to lay out the rest and hit thir dead centers. The rafters should be set at 16" centers or 24 " centers. Down at the bottom run a 1x4 close to the edge, and also at the top, it will cost a little more ,but I would put 2 screws in to each 1x4, about 1/2" to 3/4" in from each side of the 1x4 And also at the ridge cap. The 2" screws ( color ) for the metal is about 4 or 5 cents a piece around here , I just hate to think that if the strong wind got under it ( the metal ) you would find it in the next county or state. Good Luck and GOD BLESS :: F.B.E.

Thanks for the replys.

Someone nearbuy... used regular plywood decking, placed bubble wrap, and screwed the metal directly over the bubble wrap into the plywood... doesn't look like they hit rafters with the screws through metal.

Anyway, I do not like that idea.

I'm definitely leaning toward the 1 x 4' s.

But without the bubble wrap... seems like the 3/4" air space would be good for ventilation and sort of work as insulation.

Would like your thoughts on that...

I also wanted to go with YPT (treated lumber)
My concern is how will the metal react with the YPT lumber.

Any thoughts on that appreciated.

Danna

Danna - While I was still working ( REtired now )Around this area in TN. We always used the bubble wrap <the Metal Co's. Said that it keeps down from moisture forming between metal and roof, Ive built a 16x28 ft addition on front of my house and I put the bubble wrap under mine, It helps keep the heat down in your attic also.As far as using treated 1x4"s < I'm not sure it would be a good idea, No one up here uses it ,before you decide to or not ,go by Lowe's or home depot and get one of the warning papers on treated materials , you will find them hanging on the side of material racks right by the treated lumber. Ask the metal supplyier about the treated wood under the metal, On big work shops and farm blds.when we built them we useed 2x4 bottom plates ,but we would put the insulation wrap on before screwing the metal sideing on so the metal never touched the treated lumber, So Im not sure if the chemicals in the treated material would hurt the metal or not . You would be putting the bubble wrap down first so the metal would be laying right on the treated 1x4's, All the time Good luck and GOD BLESS ::Ps IVE had some metal roofs on for a good 12 to 15 years and I used regular 1x4 or 2x4 runners,and there are still looking good,and no troubles that I know of GOOD DAY :: F.B.E.

OK here is the deal:

You shouldn't screw metal roofing to wood strapping. I know, everybody does it, but there are always problems down the road.

Sheet metal expands and contracts with changes in temperature, this puts a lateral strain on the fastenings at each end of the sheet. The longer each sheet the more strain at the ends. In time, this repeated movement tends to loosen the screw in the wood, and elongate the hole in the metal. Inevitably, the rubber seal fails, and moisture is allowed to find its way to the wood strapping, causing deterioration of the wood fibers around the screw and further loosening of the fastenings. There are a couple of ways to avoid this. Put your roof on in big shingles, say 5 or 6 feet long. This way the expansion is minimized.

A better way is to use Z-section strapping made of sheet metal. The fastenings make a more positive connection, and the Zs will give to allow the expansion. Metal strapping probably won't cost much more than wood.

There are products which clip to hidden brackets fastened to the roof, leaving no penetrations in the metal membrane. These seem to be the best solution of all.

Thanks... for all replys.

Still undecided