Synthetic Roofing and a challenging roof project - pro advice needed


Howdy and Happy New Year to all.

I’m a homeowner very capable and experienced in extreme DIY projects, have built or remodeled about 7 residential and commercial structures, but it’s not what I do for a living…I thought it helpful to give some context to my level of experience in various construction trades. OK, I’ll try not to make the rest too wordy, we’re all busy…

Project: total rehab of 1899 single-story farmhouse w/a 6/12 pitch roof, post and beam so it’s gonna move a little over time…

Existing roof surface: old-school 3/4 x 8 x (various lengths) oak plank on 2-foot centers.


  1. not taken care of, some areas got wet, planks are warping here and there (what i’d consider fairly normal for a structure of this age). Also some rafters bowed and we’re fixing those as we go by jacking slowly from the inside and supporting appropriately.

  2. 20 years ago, someone did a soffit/gable overhang metal wrap and removed all the corbels, so now the 24" gable-end overhangs are unstable and have very little support

  3. I need to dry it in now, then take my time fixing it over the next couple of months

My proposed fixes:

  1. Do a tear off, install GAF or Titanium or some other synthetic underlayment.
  2. Screw down every plank with deck screws (or some other suggested/cheaper screw?) Or possibly just 2-inch galvanized ring shank sheathing nails? Suggestions here?
  3. Build gable-end ladders out of 2x6 to install underneath the 128 linear feet of overhangs that are effectively flapping in the breeze, bolt ladders to gable end wall joists with construction screws.
  4. Cut back the overhangs after they’re supported w/the ladders to 12 inches max.

**While doing all this, I’ll remove the synthetic underlayment where i’m working and re-install new underlayment, so i’ll try and work from the bottom up, a little water getting in won’t hurt as sheetrock/plaster is not finished yet

So, pro advice I need is, in order of importance:

  1. is synthetic roofing material appropriate for old wood plank roofs where nail pops my be a real concern?

  2. should i renail or screw down wood planks? (i worry about the old nails coming back out as I’m seeing some of that as I’ve done a few repairs like this and i’ve pulled them out, but pulling every old nail on every plank would be tough)

  3. screw planks back down - best screws for this or should i renail them? (honestly i’m thinking my framing nailer with 2" galvanized, ring shank sheathing nails)

  4. suggestions on best button caps and button cap gun for the synthetic roofing underlayment installation? (i need a new toy)

  5. Any other suggestions, do’s/don’ts, etc.?

**The 2 foot centers keeps 1/2" plywood replacement of all the planks prohibitive, I could go with 3/4" plywood but I’m of the mindset that the planks are fine, just fix it…

Thanks in advance,

Eric in Chespeake, VA


I would install 1/2 osb on top of the existing
With 8d ring shank every 6 inches
Making sure to hit the rafters.

I have found that the “stinger” is a fast and reliable simplex gun.
Careful of too much air pressure
And go back and flush all the nails that are not flush.


Holy crap, I didn’t even think of that. I guess that’s why they pay you the big bucks. :wink: Thanks for the reality check. That would make the job a whole lot simpler. Hopefully there won’t be an issue with the 2 foot centers.


We do mainly older work. As roof lover said Best fix over old plank is 1/2" cdx or osb. 1/2" takes out many of the imperfections but is still flexible enough to work with. Only difference is I use 10d or 12d nails. Once plywood is on synthetic underlayment will work fine. If going directly over plank I would use 30# felt.