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3 Common Reasons Roof Repairs May Not Work

If you find a leak in your roof, the hope is that a simple repair can fix it.  This is the best case scenario, but sometimes these roofs to need to be replaced because a repair won’t work.  Here are 3 of the most common reasons that trying to repair a leaking roof may be futile.

1) The substrate may be shiplap


These days, every house is built with solid 4’x8′ plywood or OSB sheathing as its roof deck.  But that didn’t used to be the case.  Up to the 1960’s, 1″x8″ fir pre-plywood shiplap was the most common.  If you have an old home, it probably has shiplap roofing substrate.

The resin in shiplap dissipates over time, and the boards shrink, leaving excess gaps between them.  If new shingles are nailed to these boards, the probability of all the nails firming fastening down the shingles is low.  You then may end up with shingle blow-off or new leaks on the repaired section.

In addition, shiplap roof decks often have multiple layers of shingles, which means a ton of nails have penetrated them. This hastens the development of cracks and brittleness.  Any freshly installed shingles will have a hard time attaching properly, and you’ll end up with another problem on your hands.

2) The sheathing may be rotting


Even if your house wasn’t built before the 1970’s, there are many reasons the plywood sheathing could be rotten, especially in the Pacific Northwest.  We have so much steady rain and too few hot days that moisture can easily get trapped on the plywood sheathing.  Also, many attics in homes are not properly ventilated, which can lead to moisture buildup on sheathing.  While current standards are pretty good for ventilation, just a few decades ago, they weren’t.  Over time any moisture on plywood for too long will lead to rot.

The problem with rotten sheathing is it loses its integrity.  So, even if the shingles over top of it are fine, you’d still have the same problem as with installing shingles over old shiplap.  The shingles are unlikely to fasten properly, and soon enough they’ll blow off or result in new leaks.

Sometimes a roof repair will still work with rotten sheathing because we can just replace the sheathing with fresh, new plywood.  That’s not uncommon.  However, unless the rot is caused by a specific, unique issue that will be solved with the repair, it’ll be likely that other parts of your roof deck are rotting as well.  This means new leaks should be expected to spring up soon, and you’d be throwing good money after bad by trying to repair them.  In which case you’d be best served by replacing the roof entirely at once, and replacing all the rotten sheathing at that time.

3) The roof may be too old


Age itself isn’t an inherent problem for a roof, but it does signify probability of problems.  As a roof ages, it begins to lose integrity.  Shingles lose granules, they crack and curl, and they generally deteriorate from exposure.  There is no known age for any roof to no longer function properly.  A roof can keep getting older and if it still functions, it functions.  However, the older the roof, the more likely it will develop a leak.  On top of that, when one leak springs up, if the roof is old, it is a sign that more leaks are just around the corner.

Trying to repair an old roof is another case of throwing good money after bad.  You can repair one leak then find another leak in a month or a year.  Then another after that, and so on.

And this will cause all sorts of damage to the substrate sheathing, or even the framing, insulation, and inside of your house.



The rule of thumb to know if a roof repair should work or not is to assess if the leak has an age related cause.  If it does, a repair is unlikely to be a smart idea since other parts of the roof will soon malfunction.  Instead you’d want a full replacement.

If a leak is caused by something other than age related issues, like a falling tree branch, a repair can be the best bet.

Whether you’re in need of a repair or a roof replacement, we can help you.  Even if you don’t know what’s going on with your roof but you’re having problems with it, we can professionally inspect and provide the best course of action for you.  If you live in the south Puget Sound region, call us at 253.445.8950 or fill out the estimate form for a free estimate at your convenience.


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