Roof leak! Eek!

October 22, 2016 4:01 PM

Two-three years ago, I had an oak branch plummet through my roof, like a spear thrown from Thor himself. Of course this was the year after my new roof had been installed, but I digress. I took a new shingle, and some of that black goo (can't remember the name) up there, and patched it up nicely....

This past week, during a torrential rainstorm, I realized the roof was again leaking. Now, it is dry, and I've looked and cleaned as much as possible...do I try and rip off the 'old' patch and do the same again? That is my first inclination. But. The spear of Thor came through the shingles and the underlying plywood, so there is a craggly hole on the underside of the roof (inside the attic) as well. I'd love to be able to just patch the roof again, and spray the plywood with that expanding insulation stuff, but not sure that's the best solution. Any and all ideas will be most appreciated, and taken under consideration immediately, since this next week is supposed to be dry! TIA

posted by PlantGoddess to Home & Garden (10 answers total)

If you actually want to fix this long term(and you do) you are going to do a better job, or bring in a pro. The plywood and underlayment needs to be patched, and the shingles(probably two) need to be replaced and actually attached to the underlayment with nails.
posted by rockindata at 5:26 PM on October 22, 2016

Response by poster: Thanks rockindata...I know that's what I need to do - I cannot afford a pro, and am fairly good at DIY, so I was asking for suggestions on how I might best approach the problem.
posted by PlantGoddess at 5:35 PM on October 22, 2016

Best answer: I repaired an acquaintance's roof after a similar, albeit more extensive, calamity. Her roof consisted of plywood sheathing covered by roofing paper and then shingles. Your roof may be of a different construction. In particular, modern roofs might have a more complex layering of materials in the roof. My repair was as follows:

1. Before starting, make sure that you can obtain new shingles to match the existing ones, as you may not be able to reuse all of the existing shingles.
2. Remove a rectangular portion of the shingles large enough to expose the penetration (including all cracks), horizontally past the rafters on either side of the damage, one row below the damage, and as many rows upward as necessary to expose the closest edge of the strip of roofing paper immediately above the damage. Shingles can be removed by gently lifting the edges of the shingles and removing the nails with a flat utility bar.
3. If you cannot pry the nails out without ruining undamaged shingles, cut the nails by sliding a hacksaw blade beneath the shingles and sawing them in two. Extract the nail heads. Flatten the stubs of the nails projecting from the roof surface by covering them with the tip of the utility bar and striking the bar with a hammer.
4. Scrape off any cement residue from the area exposed. Cut out a rectangular portion of the damaged plywood sheathing, exposing half of the roof rafter on the left and right sides of the hole.
5. Cut a patch from a new piece of plywood to fit the dimensions of the rectangular hole. Nail it in place to the rafters on each side of the hole (I used 2.5" 8d common nails).
6. Cut a piece of roofing paper large enough to comfortably cover the patch while also tall enough to tuck 5" underneath the strip of roofing paper above the damage and 5" over the paper below the damage. Secure the roofing paper in place with circular "tin caps" and either roofing staples or roofing nails.
7. Starting from the lower side, nail courses of shingles, working your way upwards (I used 6d galvanized roofing nails). Each row of shingles should cover the nails in the row below by about 1 inch vertically. Cover the nail heads with roof cement and smooth down the overlapping shingle edges. The final row of shingles will need to be tucked and nailed under the row of shingles that were not removed. Apply roofing cement to all of the shingles that had to be lifted during the repair.

That repair has held up well without leaks. The steps above may be excessive if your area of damage is small. For an area of damage smaller than a single shingle, I think the following is fine:

1. Cut a piece of aluminum or copper flashing to form a rectangle, about three inches longer and wider on all sides than the area of damage.
2. Clean the area beneath the broken shingle and coat it with roofing cement.
3. Slide the patch into place beneath the broken shingle until the patch rests against the nails securing the shingle just above its vertical slits.
4. Secure the patch in place with flashing nails near the corners of the patch. The flashing nails should be made of the same metal as the patch to prevent corrosion (purchase the flashing nails where you obtain the flashing).
5. Cover the nail heads and the entire exposed perimeter of the patch with roofing cement.

posted by RichardP at 5:42 PM on October 22, 2016 [9 favorites]

Oh, I should mention that in step #2 above, you don't want to remove more than two rows of shingles when looking to expose the closest edge of the strip of roofing paper immediately above the damage. If, after removing two rows you don't find the edge, Instead cut a horizontal slit in the roofing paper across the middle of where the top row of removed shingles had been from about 5" to the left of the rafter on the left side of the damage to 5" to the right of the rafter on the right side of the damage. Use that slit as the "edge" of the strip of roofing paper above the damage. The new piece of roofing paper should have a width matching that of the horizontal slit.
posted by RichardP at 6:40 PM on October 22, 2016

I followed these instructions to patch over a hole in my roof. I was fixing a hole from a vent pipe but same idea.
posted by LoveHam at 7:13 PM on October 22, 2016

RichardP's method is good. A critical piece of the puzzle is that you need to cut away the damaged plywood sheathing to expose half of the rafter on either side of the hole, and then you need to patch in a new piece. I would also cover the seams in the patch with an adhesive flashing such as this for good measure. Otherwise his method is pretty much exactly what mine would be.
posted by Anticipation Of A New Lover's Arrival, The at 7:29 PM on October 23, 2016 [1 favorite]

Response by poster: Thanks all- I'm off to HD after work today to pick up the needed supplies so we can make the patch attempt tomorrow!
posted by PlantGoddess at 6:04 AM on October 24, 2016

Make sure you get the right thickness of plywood! It will depend on where you live, how old your house is, and whether the sheathing was installed to code. Around here the current standard is 5/8", but it's also common to encounter 1/2" sheathing on houses that are older or where corners were cut. If you're not sure, check first.
posted by Anticipation Of A New Lover's Arrival, The at 6:10 AM on October 24, 2016

Response by poster: Repaired the roof last month, and though it has been rather dry here, we have had a couple rains that allowed me to gauge the success of the effort - all seems to be well! Thanks again for all your help and suggestions :)
posted by PlantGoddess at 10:46 AM on November 23, 2016

Thanks for the update PlantGoddess, I'm pleased everything went well with your repair. I'd love to hear if you have any details, corrections, or suggestions to pass on to a future reader of this thread that might help them make a similar repair.
posted by RichardP at 8:07 PM on November 23, 2016