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Roof Holes

June 7, 2013

As part of our entire roof project, we’ve been meeting with roofing consultants about various roofing products. We recently met with one rep that thought he had a good solution, and even better, it was one he could train us to do ourselves which would then qualify our installation for a 10 or 15 year warranty. He asked us what the existing concrete deck looked like and we honestly didn’t know. So I offered to investigate…

Which meant some roofing had to be removed. Cut some holes! I chose the location for the first hole to be on the oldest part of the roof, built in 1913.

Cutting the first hole in the roof

Cutting the first hole in the roof

I used a diamond masonry blade on an angle grinder – just in case I hit the concrete deck, I didn’t want to ruin the blade. I figured it would cut through anything else on top of the concrete, like asphalt sheets, gravel, etc.

Once I cut out about 2’x3′ rectangle in the roofing, I used a scraper tool to peel back the roofing. I thought it would be a little harder – the thick layers lifted pretty easily; as if they weren’t adhered to the concrete deck at all.

A sheet of roofing peels off

A sheet of roofing peels off

Like removing a band-aid

Like removing a band-aid

On close inspection, it looked there were only a few layers of roofing. Seemed odd because the perimeter of this roof seems like there are more layers.

Looks like only 3 layers...

Looks like only 3 layers…

Not much left to do there; the concrete felt a little damp so I just left it open to hopefully dry out before patching it back up. Now on to the second hole location…

I chose the second location specifically to span between the concrete roof constructed in the 1923 addition and the 1928 addition, which abutted each other. This would give me information about 2 different concrete decks but with just one hole.

This is why I wear gloves... spatter from the grinder blade.

This is why I wear gloves…

This roofing was DEFINITELY thicker – when I walk on this area, it’s often squishy, and sometimes feels like one of those bouncy air castles…

A few layers come up together

A few layers come up together

With that first layer tossed off to the side, I jammed my scraping tool into the remaining mess. It was wet and soft, the tool slid and made a track like it was slamming on brakes on fresh snowfall.

A soft layer exposed

A soft layer exposed

This layer was one of those roof installations where they probably thought they were taking care of things forever – it was some typical asphalt and tar, but then a layer of gravel was added to protect the asphalt and tar from sun & UV exposure. Gravel was also a “pleasant” appearance but no one could ever see this roof so that was probably not a factor.

Unfortunately, having gravel embedded in between our layers of roofing is BAD… later installations of roofing could easily be punctured by the remaining gravel from walking on the newer layers. Even the tiniest hole would allow water to penetrate, and in hot temperatures cause blisters to form between layers, and then in cold temperatures, those blisters become brittle and break. Which means leaks.

Okay enough lessons…

I peeled up those layers of paper and gravel. What remained was another layer of material that appeared to be put down in small rectangular sheets, based on the joints now visible.

A new layer is exposed - not sure what...

A new layer is exposed – not sure what…

I gently scraped off the black top layer and it exposed a light brown material. It felt like many layers of paper. And it was soaking wet. When I pressed on it, water squeezed out.

A new wet squishy layer exposed.

A new wet squishy layer exposed.

So I went to work removing this cellulose-like layer; since it was so wet, it removed as easily as scraping wet paper towels off the floor.

And then what was next looked like the final deck; or at least felt like a very hard surface.

Maybe finally through...

Maybe finally through…

I was expecting concrete, and while this material was very hard, it didn’t sound like concrete when I banged on it with the tools. So I got down close to it with some tools and banged on it some more… and then some black chips started popping off.

Up close, some black chips pop off...

Up close, some black chips pop off…

Holy bejeesus this was a layer of pitch! Pitch is a solid at room temperature, can be shattered but will sloooowly flow over time. You may know of this if you’re a science or NPR geek and have heard of the pitch drop experiment.

It was common to use tar pitch in roofing layers. It was quite waterproof if no cracks developed, and it was self-sealing in hot summers because it could melt into itself. This layer looked a bit contaminated with other materials so I was going to remove it.

But crap was it difficult!

It was like trying to chip away at frozen syrup! When i smacked it hard with the scraper, just dime-sized chips flew away. When I tried PUSHING it with tools, it resisted like cold taffy. I opted for the chipping method as it seemed easier.

Chipping away at pitch

Chipping away at pitch

But the chipping method sprayed bits of pitch everywhere! Fortunately they didn’t immediatley melt into the surrounding roof and I could sweep them up. But a few that were sitting around longer needed a little persuasion. I think any left overnight would have melted into the roof.

Chipping pitch sprays everywhere...

Chipping pitch sprays everywhere…

I eventually got all the pitch removed; at least most of it, where I could see the concrete deck. (Which was the whole purpose of this exercise anyways.)

Unfortunately, the paper-based insulation surrounding this hole was holding a LOT of water, and it easily flowed into this opening.

Water squished from surrounding insulation.

Water squished from surrounding insulation.

This would seriously hinder my hole repair procedure!

I took a moment to examine the strata of this roof. By looking at the edge condition of this hole, there was at least 60 years of various roofing installations at this location. If I were to guess, everyone before Sue & me decided that they could just keep layering more roofing on top of old roofing!

Close-up of the many layers of roofing visible.

Close-up of the many layers of roofing visible.

I hope this is enough information for our roofing consultant. All three roofing deck constructions have been exposed (1913; 1923 & 1928); and hopefully we have some good forensic evidence of the layers of roofing material currently sitting on top of the concrete. That should be useful to SOMEONE.

So I went back over to the first hole to see if I could patch it; it looked pretty dry now – at least the majority of the material was dry.


First hole looks mostly dry now…

But then, as I was gathering my roof patching materials, I felt a few raindrops… Wut the hell?! Weather forecast was for clear skies until the next day!

Within 10 minutes, it was a steady heavy rain with dark clouds in the distance, so I high-tailed it off the roof without even any more pictures! I’ll have to finish it up when it stops raining.

Stupid St. Louis weather. And now with two big holes in the roof.

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