The Roofing Expo Blog

A small leak will sink a great ship — little mistakes can create huge problems. Since my area of expertise is specifically in slate roofing, I have observed and documented many mistakes that contractors make when installing slate roofs. By documenting and illustrating some of the mistakes I have seen in the field, I hope to help others avoid making the same mistakes. Slate roofs are a wonderful architectural roof assembly, but poor installations are hurting the reputation of this excellent roofing system.
        

Most American slate shingles should have an expected longevity of somewhere between 75 and 150+ years, depending on the type of slate. The best slate roofs use a good quality slate of known origin and proven performance, fastened with corrosive-resistant fasteners such as copper, stainless steel or hot-dipped galvanized nails, attached to decks of solid wood at least 3/4” thick. Pretty simple. So what goes wrong? Well, here are some examples, in no particular order:

1) Size of slate: The smaller the slate shingle, the more that are required to cover one hundred square feet of roof — a “square.” For example, the largest standard size, 14”X 24”, requires 98 shingles per square. The smallest standard size, 6”X12”, requires 533 shingles per square. Since each shingle is attached to the roof deck with two nails, obviously the smaller slate will require much more labor during installation. If a contractor is not aware of this fact, he may choose to purchase small slates simply because they may be less expensive. In one case, this proved to be a dire error — the contractor bought 6”X12” slates for a re-roof on a 12 story building in Kansas, probably trying to save money on materials, then he went bankrupt halfway through the job, no doubt because his labor costs were sky-high. Find sources of new slate.

2) Type of slate: Ideally, the slate selected for a project is a tried-and-proven material with many decades of outstanding performance in the field, manufactured by a company that takes pride in its product. Most American and Canadian slates fall into that category. However, there are many foreign slates entering the American market these days with little or no history of performance. In one recent case, a very large two-year-old roof installed with Chinese black slates faded, or changed color dramatically to create a splotchy, unpleasant black/white appearance. The entire roof had to be removed and reslated at great cost. This is not to suggest that all Chinese black slates will do this, but obviously some will. Selecting the correct slates can be very tricky when the slates come from another continent and you can’t trace their origin back to any particular hole in the ground.

Some Spanish black slates are known for their pyrite content, which will bleed red rust stains down the roof. A large residence in Florida suffered such stains on a one-year-old roof. This residential roof had to be completely reslated, at great expense. The owner of the residence selected this slate because he liked the shade of black, not understanding that some slates can change in appearance with exposure to weather. When selecting Spanish slates, it is important to know whether those being considered are pyrite-bearing, a condition that may or may not be obvious by visual inspection. In a recent case on the east coast, an entire church roof had to be reslated because the new Spanish black slates were bleeding rust down the roof and the church people did not like the way it looked. Again, this is not to be construed as a condemnation of all Spanish black slates, as some are quite good.

In another case, Spanish black slates were ordered for a large roof, but they were not all from the same origin. Although they looked the same sitting in the pallets on the ground, once they were installed on the roof, they created a slightly mottled look that was unacceptable to the property owner. It’s hard to say who to blame this mistake on — the supplier, who should have known they were not sending the same material to the job site, or the contractor for not rejecting the slates due to obviously different pallet markings suggesting slates of different origins. The contractor could also have prevented the unsightly, patchy mottling of the roof by thoroughly blending or shuffling the slates before installing them. This would have allowed for a uniformly mottled effect that is pleasing to the eye.

3) Opening pallets: Even if the slate is all from the same source, different pallets can contain different shades of slates due to the location of the rock strata or other factors related to the quarrying of the material. Therefore, when the slate is delivered to the site, all of the pallets should be opened from the outset and slates taken simultaneously from each pallet in order to blend the entire inventory and create a pleasant appearance on the roof. It is a mistake to start with one pallet, install those slates, then open another pallet, install those slates, etc.

4) Cull out bad slates: Poor quality slates can originate from any quarry. This may be due to the manufacturer not culling out rejects, for example. Shoddy quality control can lead to rusting pyrites on even the best American slates.

5) Buy from a conscientious source: There are other nuances related to the manufacture of roofing slates that can affect quality and longevity. Direction of grain and nail hole placement are two examples. A good manufacturer will be aware of these nuances and strive to produce top-quality slate. It pays to buy from such a slate source.

6) Don’t reinvent the wheel: Styles and methods of slate installation can vary greatly, but one important point needs to be emphasized: if it’s longevity that’s desired, then the installation system should be based upon known methods and materials that have proven themselves. A solid, not laminated, wood roof deck, with the emphasis on correct slate and flashing installation and not on underlayment, has proven to provide exceptional longevity. Such traditional methods and materials can easily be replicated today, yielding the same degree of success.

7) Get the starter course right: The starter course is the very first row of slates to be installed. Starter slates are invisible once the roof is completed because they’re hidden underneath the first two courses of slate. The starter course slate should be installed face down, unlike all the other slates on the roof, which are installed face-up. This is the traditional installation method as it allows for a clean drip edge where the starter slate meets the first course. Inexperienced installers often put the starter course face-up. Often, the cant or shim strip is missing underneath the starter course. Starter slates must be angled on the roof in order to match the angle of all the other slates in the field of the roof.Typically, this was done by installing a wood strip, but it can also be achieved by using a metal drip edge with a cant formed into the metal, or even by raising the fascia. Another common mistake on starter courses is a lack of headlap, especially when the field slates are turned sideways and used for starter slates.

8. Get the headlap right: If the headlap is missing or inadequate, the roof is probably going to be condemned. Headlap is the overlap on each course of slate by the second course above it. This overlap is what prevents the roof from leaking. Three inches is standard, but headlap can vary according to the slope of the roof. There is no fix for a headlap inadequacy other than to rip off the entire roof and start over.

9) Watch your lateral overlaps: Lateral overlaps, or sidelaps, should also be 3” minimum. However, don’t be surprised to see slates with no lateral overlap at all. Incorrectly placed sidelaps can leave the butt-joint directly over the slating nails. This will allow direct water entry through the nail holes.

10) Avoid over-nailing and under-nailing: Another common installation mistake is the overnailing and undernailing of the slates. Slate nail holes are meant to be crater-shaped to allow the nail head to sit down inside the slate. Otherwise, the nail head will protrude above the slate and rub against the overlying slate, eventually creating a hole. When the nail isn’t driven far enough, this is known as undernailing. Overnailing, on the other hand, is when the nail is driven too far and breaks through the slate. This leaves the slate hanging on one nail or sliding out altogether.

11) Use the right nail length: Nail length is an issue that is commonly off the radar screen of the average roofing contractor. The slating nails should barely penetrate the roof deck boards. If the nails are too long, they break through the back of the boards and splinter out the wood, reducing the board thickness where the nail is located and undermining the effective holding power of the nail. Proper nail length is twice the thickness of the slate plus one inch.

12) Stage the roof correctly: A very common error with new slate roof installations is what I call the Bigfoot Syndrome — roofers walking on the slates during installation. An experienced slating crew will make every effort to keep off the slates during installation by staging the roof correctly. When Bigfoot walks all over the slates, the shingles crack and break. They may not fall apart immediately, but I have seen a hundred slates fall off a new slate roof within five years after installation due to the Bigfoot Syndrome.

13) Install flashing correctly: Flashings provide all sorts of opportunities for error. Negative overlap, for example, is sure to leak. Uphill flashing should always lap on top of downhill flashing. When lower flashings lap on top of higher flashings, water can enter the roof. Corner joints on roof penetrations are also commonly flashed incorrectly — chimneys provide a perfect example. The corner flashings must either be correctly folded, or else soldered in order to prevent leakage there. If a corner isn’t folded or soldered, then the only thing keeping it from leaking would be caulk or sealant, which does not have adequate longevity. This is a leak waiting to happen. Dormers also often have corners that need to be flashed. Without the knowledge of folding corners or soldering, a dormer corner can be left wide open and waiting for the first good rainstorm.

14) Allow for metal expansion: Common on many slate roofs are built-in gutter systems. “Box gutters” require expansion joints, but they’re often installed without any allowance for expansion whatsoever. This becomes evident by the failure of the solder joints, which are often roof-cemented or caulked after they start leaking in order to alleviate water penetration. Expansion joints can be added after the gutters are installed, but it’s a lot easier to install them correctly in the first place.

15) Use compatible metals: A common sight on new slate roof installations is metal incompatibility, often steel and copper used together. The copper will “eat” the steel, causing steel fasteners to degrade at an accelerated rate.

16) Throw out magnetic rivets: Many roofing supply outlets sell copper rivets with copper-plated steel mandrels. When the rivet is installed, the steel mandrel breaks off inside the rivet, lurking there to eventually rust and create a hole in the flashing. These rivets look like they’re made of copper, but they aren’t. Check them with a magnet to be sure. Copper is not magnetic, but steel will stick to a magnet like glue. Copper rivets should have brass mandrels, not steel. If they’re magnetic, pitch them.

17) Don’t solder with an open flame: Open-flame torches should never be used to solder flashings on a roof, so if you see a worker on a slate roof soldering a box gutter, for example, with an open flame plumber’s torch, say something. The flame is too hot and will ignite the substrate, be it felt paper or rosin sheet, which will then smolder underneath the metal, perhaps unnoticed until it’s too late. If the smoldering is noticed, panic will ensue because there is no way to get to the fire without first ripping out the flashing. The correct tool for a soldering job is a closed-flame soldering device, or a heavy-duty electric soldering iron. Open flame devices can be used on external copper gutters, however, because the metal is not in contact with the roof.

18) Hang gutters below plane of roof: Speaking of gutters, they’re often hung too high. The outer edge of external gutters should be below the plane of the roof in locations where snow or ice could slide down the roof and knock them off.

19) Use enough snow guards: Snow retention systems are another source of problems when they’re installed incorrectly. One of the tricks for a proper snowguard installation is to use enough of them. Otherwise, they won’t be able to hold the weight of the ice and snow and will rip out, taking slates with them. Follow the manufacturer’s guidelines when installing these popular slate roof elements.

20) Use the correct tools: Incorrect tools can be the downfall of many a would-be slater. Slate roofing has its own unique set of tools and equipment. For example, slates should be cut with, you guessed it — “slate cutters.” A slate cutter will leave a beveled edge on the shingle, allowing it to match all the other shingles on the roof, all of which have beveled edges. If a diamond blade is used to cut the slates, a square edge remains, which can stick out like a sore thumb and get a roofer into trouble if the property owner doesn’t like the look of it. Square edges could be dressed with a slate hammer and stake to give them the proper appearance, but one has to first have these tools in the tool box.

21) Install underlayment *under* slates: I looked at a new slate roof where a first-story section had been installed with self-adhering underlayment (ice membrane) pasted over top of each course of slates before the next course was laid. You couldn’t see the underlayment because it was covered by slates. That winter was a bad ice year and an avalanche fell on the first-story roof, damaging the slate. I was asked how to repair it. “Rip it all off and reslate it,” was my advice. There is no way to repair a slate roof that has been glued together like that. The beauty of traditional slate roofs is that they are like cars, you can remove any part and replace it, and in so doing, you can keep such a roof alive for centuries. Glue the roof together, then try to take it apart for later repair or restoration. It isn’t gonna happen.

Hopefully, you’ve gained some knowledge from this little sampling of slate roof mistakes. Slate roofing is not rocket science, and any reasonably intelligent person who takes the time to become informed about the topic will be able to successfully install a roof sure to last for generations. There are plenty of slate roof resource materials available both in print form and on the internet. A couple hours of research can save a roof installer a lot of headaches, prevent high blood pressure and ulcers, and keep him out of litigation. I long for the day when every slate roof I survey is free of major defects. In the meantime, I won’t be holding my breath waiting. This information came from http://www.traditionalroofing.com/TR7_errors.html.

The other night my wife and I were out for dinner at a local Mexican restaurant. I couldn’t help but notice a young couple and their children settle at a table near ours. Mom and kids were dressed in summer attire and dad was still in his business clothes complete with white shirt and tie. The kids, ages two and six were well behaved … but the dad wasn’t.

Dad sat there at the table, working his ‘smart phone’ pretty hard. Seemed to me he was looking at and responding to email while ignoring his wife and kids for about ten minutes – quite the multi-tasker.

Dad isn’t the only person multi-tasking these days. Have you ever seen a television camera shot of the fans at a major league baseball game? There always seems to be a handful of people on their cell phones or texting, tweeting, emailing or something – maybe they’re playing a game?

We see these preoccupied multi-tasking people everywhere. While we’re driving, shopping, at movie theatres, walking down the street at social gatherings … seemingly everywhere!

Maybe dad should put his phone away and engage in conversation with his family. Maybe he should listen to what they have to say and answer their questions instead of those from an email message that can probably wait until later that night or first thing in the morning.  

Here’s a suggestion, put your phone away. Engage in conversation with those around you - listen … watch the ballgame or the movie. If no one is around, take the time to think …yes to think … and to plan. There is too much ‘doing’ and not enough thinking or planning going on these days.

Great leaders are masters of thinking and planning and usually excel at personal productivity by being focused.

I’m looking forward to sharing my strategies to help everyone ‘become personal productivity champions’ at the 2012 IRE in Orlando on February 24^th – I hope you can make it.

Randy Goruk develops leaders through his coaching, training and speaking. He is author of Sparks—A Business Fable.
Email randy@LeadersEdge360.com or visit www.LeadersEdge360.com

Any roofing contractor that performs new construction projects has encountered a job that entails installing insulation and a roof system over newly poured structural or lightweight structural concrete. Roofing contractors are typically directed by the General Contractor to install the roof system in order to facilitate interior work. Typical industry criteria recommend cure times of 28 days or more, depending on the amount of moisture the concrete is exposed to during the cure period, and often times, roofing contractors are directed by the GC to install the roof prior to proper curing of the concrete. The designer of the concrete mix should specify the proper cure time of the mix, and General Contractors should keep this cure time in mind when scheduling the project.

 Many problems have been borne out of projects where the concrete mix was not given sufficient cure time. Some of these issues are: adhesion of the roof insulation to the concrete; deterioration of bonding adhesives securing single ply roof membranes to an insulation or cover board; warping and/or cupping of the insulation because of moisture release from the concrete mix; and, mold growth on paper insulation facers due to the amount of moisture retained in the roof system (obviously, once the roof membrane is installed the moisture released from the concrete mix stays within the roof system). Unfortunately for us roofing contractors, the fingers get pointed back to the roof system regardless if the system is watertight or not.

 In an attempt to alleviate moisture related problems in these instances, a few guidelines should be followed by all parties involved in the project. First, and most obvious, is for the designer of the deck to specify a cure time, and all parties adhere to the specified time. Second, testing for adhesion to the roof deck should be completed…as stated in the NRCA Roofing Manual: Membrane Roof Systems 2007, “If a dry surface cannot be obtained within a reasonable time period, direct membrane adhesion should be postponed, or alternate roof securement methods should be considered.”  While this statement is prescriptive and does not define methods of adhesion testing, it is a good guideline. I suggest that a vapor retarder that is partially adhered to the concrete (allowing lateral movement of latent moisture) deck be considered prior to installation of any roof insulation. Finally, if the system is to incorporate polyisocyanurate roof insulation, polymer filled glass facers should be installed. These types of facers do not promote mold growth because they do not contain organic materials. They also tend to provide more stability for the foam core, reducing warping and buckling of the ISO insulation. 

 The Technical Operations Committee of the NRCA is becoming informed of problem jobs over newly poured concrete more and more, so I urge roofing contractors to use caution on these types of projects. The National Roofing Legal Resource Center produced a document entitled “A Roofing Contractor’s Guide to Bidding” that can be helpful when encountering a new construction project over concrete roof decks by explaining that a moisture-related issue may arise from this type of construction prior to submitting a bid or signing the contract for the project. As our industry becomes more competitive, complicated and litigious, roofing contractors must protect themselves from potential liabilities. This issue may not have been created by the roofer, but it can be extremely costly for the roofer to defend unless we complete our due diligence.

Author:

Scott Baxter, Vice President, CRS Inc., Roofing & Waterproofing Specialists

If a picture is worth a 1000 words, the quality of an image is worth millions when applying remote measurement technology. An overriding misconception is that remote roof measuring only uses satellite images. In actuality, the most accurate method used by leading roof measurement companies is the use of aerial photography.

 According to Chris Pershing, the inventor of the patent-pending EagleView® software, it is as simple as the resolution or the closeness of the image, “Some satellites are able to produce higher resolution images. However, the U.S. and many other foreign governments restrict the resolution of commercially available satellite images. In the United States for example, commercial satellite images are limited to 0.5meters/pixel (18 inches / per pixel).”

 “In contrast, aerial images are not subject to the resolution limits imposed on satellites,” continued Pershing. “Aerial images are available at resolutions down to 4 to 6 inches per pixel for most of the populated areas in the US. Moving out to lesser populated areas, aerial images are also now widely available at 12 inches per pixel, still significantly better than satellite.”

 To clarify how pixels relate to distance, according to Wikipedia, “The resolution number represents the distance covered by one pixel in the image. Therefore, a 1 meter image is an image where 1 pixel is equal to 1 meter. A 1000 x 1000 pixel image at 1 meter resolution would cover an area 1000 meters by 1000 meters, or one square kilometer.”

 EagleView Technologies uses the resolution as a key part in developing the 3D diagram from which they gain their highly accurate measurements. The most important factor to accuracy is resolution. The lower inches per pixel the higher the accuracy in the measurements. Thus, the ability to be at 4 to 6 inch resolution with aerial photography compared to 18 inch resolution with the satellite images means aerial images can provide several feet in improved accuracy when providing roof measurements.

 “For roof measurement applications, an 18-inch-per-pixel satellite image would be the choice of last resort when no suitable aerial image was available,” Pershing noted. “At 18 inches per pixel, many details of the roof are poorly resolved. This lack of detail can significantly increase the uncertainty of the measurements. As such, the viability of those images for any particular building measurement would need to be evaluated.”

  “Although, satellite imagery is available for nearly every location on the earth most satellite image libraries target vast areas at very low resolution. Each pixel (or dot) in those images may represent an area as large as a car, a house, a city block, or a square mile — far too coarse to be useful for measuring details on a particular building. Satellite images can be used but only as the last option,” said Pershing.

 By Heidi J. Ellsworth, VP Sales and Marketing, EagleView Technologies

Join us for the Int’l Roofing Expo Session “Using Aerial Measurement Technology to Improve Roofing Business Practices” taking place on Wednesday, February 15 from 7:45-9:15 am. For more informatoin on this session, visit our website at http://connect.theroofingexpo.com/connect/public/nz_ALSessionSearch.aspx.

This session is being presented by Chris Barrow, President and CEO, EagleView Technologies. Chris has over 20 years of experience in software, technology and services sectors. Most recently he served as CEO of a publicly traded technology company in Orlando. He has also served as Executive VP of Sales, Marketing and Business Development for several companies in the US and Asia, including senior sales and business development roles at Sitel, 3Com and Compaq.

Experienced contractors have always recycled jobsite materials, but with more and more new construction using the US Green Building Council’s LEED® certification method, approaches are becoming more formalized.  The good news is this doesn’t just mean more paperwork, but can also mean improved economics – as many of the recycled materials have value – and can also mean improved community relations as well as a cleaner, safer jobsite.  One of the best ways to increase construction waste recycling is to write a Construction Waste Management Plan (CWMP).  This fairly straightforward document, often just one or two pages long, lists each of the major waste streams on site – typically wood, cardboard, cement/concrete, metal, insulation, plastics, and general debris -  and how they will be handled, whether recyclable or not.  The CWMP can be shared with everyone on the jobsite, including all subcontractors, and is effectively a requirement on LEED projects.  I’m always interested in learning more about this topic, so when I happened to notice a busy jobsite with a row of 6 neatly labeled dumpsters – calling out to me “Recycling happening here!” -  I knew I had to stop in and learn more.

The Project Superintendent, Grit Richards of Pizzagalli Construction Company, was courteous enough to lend me a hardhat and show me around the project.  Pizzagalli is one of America’s largest employee-owned construction companies, and with offices in Vermont, North Carolina and Maine, the company completes projects all along the east coast, for a five-year volume average of more than $450 million, and has extensive experience with LEED.  The project I happened to visit was pursuing LEED Silver, and here’s what Grit had to say about setting up the jobsite recycling program:

“We design a lot of projects to include the recycling, even ones that aren’t LEED, we do it anyway.  It usually doesn’t cost any more to do, and it’s important to our company.  Cost-wise, cardboard is generally a wash, and metal may even get you a credit.  Sometimes it might cost a touch more for the extra bins, but our company wants to head that direction, it’s the right thing to do.

“This is my 5^th LEED project, so I’m fairly accustomed to the paperwork.  We have a spreadsheet where we keep track of how much waste is diverted from landfills.  LEED requires documentation not just that the material was hauled but where it ended up, including a contact name, so they can verify recycling.  We use a Construction Waste Management Plan, and we review the recycling arrangement with all subs at their jobsite orientation, and have the waste hauler attend our meetings, so they know our requirements.”

Here’s a picture of the recycling arrangement.  You can see that it’s not complex, just a row of collection bins labeled with each material, not unlike recycling at home.  And the crew here is doing a great job recycling, with almost all of the material that arrives onsite and doesn’t become part of the structure having been diverted from the landfill.  Grit receives a monthly statement showing the diversion rate, and this project is currently running at 97.19%, well above the 95% required for Exemplary Performance in LEED 2009, and moving the project three points closer to the minimum of 50 needed for LEED Silver.

Grit also shared a couple of good tips with me:

• Make the signs on the bins removable – so they can be taken off and exchanged when the bins are emptied.
• And put the General Debris bin the farthest away from the work area – make it easier to recycle materials than it is to throw them away – a classic real-world tip.

You can find a lot of example CWMP’s on the web.  Here’s a link to one of my favorites, which you might use as a starting point to develop your own, and here’s a good review of the topic generally.  It’s worth noting that the installation of roofing often generates very little construction waste – in fact, Grit wasn’t aware of any waste, besides packaging, generated during installation of this project’s reflective TPO roof.  But the packaging can add up, so there’s still plenty of cardboard boxes and cores, pallets and other packaging materials, as well as any metal flashing cutoffs, that can be diverted from the landfill.   And of course any job that will involve roofing tearoffs should look into recycling.

Author: Martin Grohman, LEED® AP, GAF Materials Corporation, graduated from Rensselaer Polytechnic Institute, with a BS in chemical engineering.  He was the founder of Correct Building Products LLC, the manufacturers of CorrectDeck composite decking – longtime leaders in building products recycling programs, and sustainability in general.  In 2009, the company was acquired by GAF, and Marty joined the GAF team as Director of Sustainability. Prior to founding Correct Building Products, Grohman worked in extrusion technical service for Cincinnati Milacron, and in plastics for General Electric.  He has presented at numerous industry events and contributed to magazines such as Building Products Digest, The Journal of Light Construction, and Professional Deck Builder.

Martin will be speaking at IRE on “Increasing Profits with a Construction Waste Management Plan”. For more information, visit www.theroofingexpo.com.