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Some resources collected while investigating and then replacing my roof.

See also:

See AboutThesePages.




I should provide some background on my house, roof, and geographic location:

  • Two story colonial, attached two car garage with family room behind -- back of house faces south -- eastern Pennsylvania, USA, (Bethlehem).

  • Original roofing was black, installed between Sept and December, 1979, asphault shingles, probably 20 year rated -- replacing them in Oct, 2002. Underlayment is black tarpaper (15 lb.), decking is 1/2" (15/32") plywood (although they may have used something heavier in front??)

  • Drip edge, flashing, gutter details later
    • One problem area is where 2nd floor downspout dumps water onto 1st floor roof (north and south decks) -- needed to replace several (whole or partial) pieces of plywood on both decks. In reroofing, I'm covering up through that area with the Ice and Snow guard (?) including 6 to 8' from wall (need a sketch). Also, I plan to rearrange the downspouts to put water directly into first floor gutters.

  • I ordered 23 squares of shingles -- need to find my original measurements / calculations -- I think I ordered too many -- used less than I expected on the one section I've done so far. Oops, may have ordered too few for 2nd floor, and net too few.

  • 4 "logical" sections
    • 1st floor, back -- 21' wide by 21' "tall" main deck -- small additional section at south west corner about 1' by 3'. Chimney, 1 1/2" vent stack, and butts into 2nd story wall along west edge.
    • 1st floor, front -- 21' by 21' main deck, additional section over porch at north west corner, about 14' wide by 5'. Butts into 2nd story wall along west and north edges.
    • 2nd floor, back -- 35' 3" wide by 16' 4" main deck, several vent openings (one 1 1/2", one 2", and one special for bathroom vent).
    • 2nd floor front -- 35' 3" wide by 16' 4" main deck, two vent openings -- one 3" and one special vent opening for bathroom vent.

Estimating Ondura sheets

Just thinking about my next roof--should be 10 years away.

Ondura sheets are 48" wide by 79" long. Figure 44" per sheet to allow a one corrugation overlap widthwise, and 72" per sheet to allow 7" overlap vertically (well, you know what I mean).

This was just a first pass, with errors--I need to review it again before being ready to order materials.


  • two decks, 21' x 21' will require: 2(decks) x 6(width) x 3.5(height) = 42 sheets
  • two decks, 35'3" x 16'4" will require 2(decks) x 10(width) x 3(height) = 60 sheets
  • one deck, 14' x 5' will require 1(deck) x 4(width) x 1(height) = 4 sheets
  • one "deck" 3' x 1'--I should have enough scraps to deal with that

Total: 106 sheets

Ridge caps: (6'7" long, with 7" overlap gives 6' of coverage--will also need these for the small decks to nail into the walls, I think)


  • 1 21' ridge = 3.5 caps
  • 1 35'3" ridge = 6 caps
  • 1 15' wall closure = 2.5 caps
  • 1 3' wall closure = .5 caps
Total = 12.5 ridge caps


  • 24 nails per sheet x 106 sheets = 2,544 nails--ok, that is for low wind areas--and I don't even think that is right--well, sort of, not counting nails that go through two sheets (or more) due to overlaps--24 nails per sheet will not be enough--atm, I don't want to figure out how many--partly because I presume the 38 nails per ridge cap will do
  • 38 nails per ridge cap x 12.5 caps = 475 nails
Total = 3,019 nails

Closure Strips (they come vented or not):

  • 21' x 2 + 35'3" x 2 + 15' x 1 + 3' x 1 = 130.5' / 44" = 36 closure strips

oops, that is not enough, as I need them at the ridgeline as well as the eaves, so that might be 72?

Do I want tile rake trim--oh, or is that only for tiles...

And, oops, again, I'll need extra sheets for pipe flashing--looks like sheets get doubled there (in addition to the Ondura flashing and "real" flashing, iiuc). I'll need 6 pipeflashings. I don't yet quite see exactly what is required for each one. Ok, I'm seeing more--sheets are doubled at each of these, so that is 6 more sheets.


  • avoid installation below 35 degrees F
  • to pull nails if it becomes necessary, lay a 1 1/2" dowel or pipe in the neighboring corrugation and pry against that
  • hmm, it cautions against installing over rotted or unstable decks--but if I have to do any repairs to the deck, then I have to reshingle that area to match the rest of the deck (assuming I want to leave the old shingles, which is what I am thinking...)

Questions and Answers

See ResourceRecommendations. Feel free to add additional resources to these lists, but please follow the guidelines on ResourceRecommendations including ResourceRecommendations#Guidelines_for_Rating_Resources.

Part of this will be divided up into resources that helped address special questions I had (these are not the only questions that should be considered):

Working in wet conditions

I hoped that I could apply shingles to wet underlayment that I had applied to keep the deck dry -- sounds like I should let it dry out first, and then, depending on how wrinkled the underlayment is, consider replacing it.

Google search on [roof shingle wet] provided some good resources including:

  • RoofHelp.com: Hints & Tips for Asphalt Shingles -- looks like a good resource with good suggestions -- underlayment nailing pattern, applying dry shingles to avoid blistering, 6 nails in high wind areas, etc. -- other pages probably worth checking out

  • DreamRoofs.com: APPEARANCE ISSUES: What are the black streaks on my roof? and other questions including things about fishmouthing, curling, applying wet shingles on a dry day or dry shingles on a wet day cause problems, which may imply that applying wet shingles on a wet day may not be the worst thing in the world (??) -- another useful looking site that may be worth more browsing

Darn -- was using IE on Windows (because Mandrake had slowed down badly -- IE crashed and I lost two or three entries I made here -- no sense looking for them now -- if I ever need them again I'll do the Google search again. (There are a few open references over on Mandrake -- I'll collect those yet.)

Drip Edge Over or Under Underlayment?

From a Google search on [roof "drip edge" underlayment]:

  • Hometime: Roofing: Underlayment & Flashing -- on eaves (bottom edge of roof), flashing goes under underlayment, on rakes (side edges of roof), flashing goes over underlayment. Not sure if this is totally for water drip behavior or partially to avoid blowoff of underlayment at rakes.

Working in Cold Conditions

"Normal" shingles should not be installed below 40 degrees F (to avoid "cracking" of the "backing")

Edge to edge spacing of shingles

Leave 1/16" spacing between shingles (to avoid one potential cause of buckling)

Avoiding Blistering

Avoiding Moss / Algae Growth

Decking Condition

Google searches I'm trying: [roof deck plywood cracked], [roof deck overlay],

Roof Support

Plywood Specifications

Plywood Weight

One source provides a rule of thumb that a sheet of 4x8 plywood weighs 25 lbs per 1/4 inch of thickness.

Here's a source of more precise information, unfortunately in kg/m2.


Some are for all sorts of handyman work / home repairs.

See ResourceRecommendations. Feel free to add additional resources to these lists, but please follow the guidelines on ResourceRecommendations including ResourceRecommendations#Guidelines_for_Rating_Resources.


  • (rhk) BuildFind: Ask a Builder -- looks like a good resource -- among other things a lot of homeowner's questions with answers.

  • (rhk) [[][]] --
  • (rhk) [[][]] --

Recommended for Specific Needs

  • (rhk) A Home Owner's Guide to Buying a New Roof; National Roofing Contractors Association -- Includes some good advice on hiring / working with a contractor (checking his insurance, etc.)
  • (rhk) General Installation Instructions for Atlas Felt Underlayments -- another (different) reason for underlayment -- to keep the shingle from drying out prematurely -- a roof really is a complex system
  • (rhk) What Roof Owners Should Know About Contractors -- good warning, and a pointer to a page for identifying "Neanderthal" contractors (which I didn't check out)
  • (rhk) US Inspect: Roof Systems -- worth checking out (I think) -- a(n inspection) company -- should be a useful perspective
  • (rhk) Roof Refurbishment Using Liquid Waterproofing Systems -- not read, but sounds interesting as it can be used on flat or pitched roofs
  • (rhk) Do I Need a New Roof? -- short page with pictures of some common problems (curling, clawing, ...)
  • (rhk) Common Failures in Wood Structures -- interesting, and one tidbit on a leaky roof that is not a leak (condensation)
  • (rhk) Roofing Material Comparisons -- interesting, especially for the reason that agricultural (metal) panels are not recommended for a residential roof: "The expansion and contraction factor of metal roof panels is so great that the fasteners can become loosened causing panels to blow off. Expansion and contraction can also cause the holes around fasteners to become enlarged, causing leakage."
  • (rhk) 372 Re-roofing and Repairs; Texas Department of Insurance; Code Interpretation 372 (RC-9) -- among other things: "When re-roofing, care shall be taken to ensure that the existing deck and other members are not damaged. Re-roofing over a damaged roof deck or roofing member will not be accepted. Replacement of damaged members shall comply with previous guidelines." There is a similar page on new roofing (http://www.tdi.state.tx.us/company/wind/wsguide/370wsg.html#top) and probably other useful pages Are these pages an interpretation of the BOCA code? Is the BOCA code itself online here or somewhere else?

Recommended by Others

  • (rhk) [[][]] --
  • (rhk) [[][]] --

No Recommendation

  • (rhk) Natural Handyman -- could be a good resource -- got lots of hits to it from BuildFind, but the pages always seemed to have a changed name (thus I never found them)
  • (rhk) [[][]] --

Not Recommended

  • (rhk) [[][]] --


  • () RandyKramer - 31 Oct 2002
  • <If you edit this page: add your name here; move this to the next line; and include your comment marker (initials), if you have created one, in parenthesis before your WikiName.>

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