Pedestal Systems

Above: A failed TPO deck with pavers being replaced. You must consider the build before the cladding and the finishing, lest all that you have built atop is not able to be supported by the deck construction. Don’t just take our word for this, go to the internet like we did and let’s see what the world’s largest search engine says about this topic:

You really only have two sensible options for traffic-bearing roof decks. Our Fiberglass decks are tough and resilient and they are done by professionals. Click the "Contact Us' button for a free exavluation so that you can be armed with our extensive report that will put all the information in your hands.

Hidden Potential Problems

We want to be fair so we have included search engine results for our query: “Is tpo a traffic bearing roof deck membrane, and can it be punctured or have seam failure. So, before you make a decision you may come to regret, please consider that you must start with a solid deck build. Then, you must have a contractor with the experience to deliver a ‘Once-and-Done’ roof deck build that will add value to your home, versatility and usability for your deck, and peace of mind for your soul. No longer should you worry about all the hidden things that can leak and destroy your beautiful home. Call on us by filling out the form page linked to the ‘Contact-Us’ buttons. ”







Much of the information listed above was taken from artificial intelligence-driven search engines that scour the internet for information. Do your research and make sure that you are getting the right build.

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Softer Membranes

FIBERGLASS

Since 1930, when it was first used as an insulation product to shortly after that in when the first fiberglass-polyester boat was built and put into service, fiberglass has been an amazing composite. Since that time, fiberglass has been used in just about every industry. Exterior cladding is where this cladding shines as it produces a very tough monolithic membrane, and all flashings can be created in the field. Fiberglass is the very toughest by far of any roof deck membrane. No Drip Edgings to be sealed; No unsightly Seams to be sealed (every seam has a leak potential); Absolutely one product without connections to unlike materials; Much less chance of a leak; Proven 20 – 30 year life expectancy. The downside is that there is a very steep learning curve and installation can be challenging for the inexperienced. The membrane is created in the field, so not just any contractor has all that is required to deliver a lasting job. Be very careful with whom you engage because you want a company that will be here tomorrow if you ever need service. Only a company that walks you through every detail and has a track record should be considered.

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FIBERGLASS -or- PVC ->Using anything other than approved materials can prove to be a huge mistake. The ‘roofing only’ membrane specifications of the 3 types of unapproved membranes for traffic-bearing applications we have listed are being actively specified. How do we know? We are getting the questions from potential clients. There is also a lack of understanding of manufacturer recommendations for the build of a roof, as opposed to a deck. Roofing systems only require one layer of plywood. Decks require two layers. You need a minimum of 2 layers of plywood in order to build a deck. Deck failure, and with replacement being so expensive, scrutinizing the specs. It is certainly recommended prior to signing a contract. The ‘roofing only’ membrane specifications of the 3 types we have listed are just the beginning of the shortchanging on the builds for ‘roofing only’ applications and have nothing to do with the proper substrate build to hold a deck. Deck deflection is a big deal, and just because you have a softer membrane that is more malleable is not a reason to compromise on the build. (- more on building a deck substrate below.)

PVC

Non-traffic ‘roofing only’ versions of PVC membrane originated in Europe in 1966 from a company named Trocal, which, by all reports, went very well. In just a few years, the USA had its own PVC roofing membranes being produced here. Many failures were realized because of the lack of plasticizers in the mix. This eventually leveled out to now 30 years of good service to the roofing industry. Variations were invented for the ‘traffic bearing’ marketplace, and several manufacturers have offerings, but the specifications are not uniform across the board. PVC offerings have many variations in color and patterns to enhance the appearance of their products. A homeowner must be diligent in scrutinizing the specifications of the substrate build, the contractor’s experience level & all of the flashing details, of which you will become aware as you continue to read the information on this page. A good build will have a nominal 3/4 inch structural substrate and a nominal 1/2 inch floor layer, and this is the minimum. Do not compromise on this lest your new roof deck fail.

FRAMING

Framing: Your framing should be minimum kiln dried Hem/Fir 2x8 or 2x10 placed on 16 inch centers. If your home was a new build from the ground up, you can be fairly certain that L&I inspected and made sure the framing was correct. You should also have a row or two of solid bridging to even out the load, etc. If your home has an addition and was not built completely from the ground up, we sometimes see sub-par work with joists that are not to code and placement that may not meet code either. Pre-job Core Cuts are sometimes in order and we use these to prevent surprise cost overruns.

Engineered joists are very strong but decay very quickly when they have gotten wet. Replacement costs can be extreme in these cases because standard methods of ‘sistering’ joists will not work, necessitating full replacement.

Plywood Layers

It is absolutely mandatory that your deck be built with a minimum, 1 layer nominal ¾ inch plywood structural layer & 1 layer nominal ½ inch BC finish grade plywood top sheet. Because of the gray areas with specifiers recommending ‘roofing only’ builds (as we have noted above), we have single-layer plywood conditions and failed roof decks. The builders are now just about all privy to this 2 layer requirement, and we have just about educated the builders to use the two layers. Now we have the newbies coming into the marketplace with single-layer ‘roof-only’ TPO certifications for ‘roof-only’ certifications and even some PVC applicators installing on single-layer construction. (Not all PVC membrane manufacturers call for 2 layers of plywood, & this is a recipe for early deck failure). Build your roof deck properly, after all, it is a deck and it needs support. Make sure that the plywood is fastened properly, with the proper amount of screws (not nails). Clad it with fiberglass, the toughest of all membranes.

(Above) Core Cut prior to job start to ascertain underlying conditions. We just happen to have a paver system over a failed TPO here in this image.

Fastening with Screws - Never Nails

Roof deck plywood should be screwed and never nailed. With pneumatic nailing, there is no feedback, so the operator has no way of knowing if the fasteners are connecting with the framing. Often, we find roof decks deflecting and cracking from poor attachment. Two layers of plywood accentuate this effect. Plywood needs to be secured, and if not, you will have deck failure early in the life cycle. The placement and the number of fasteners used are critical issues that point to the quality of the build. Nailing rate is 6 inches on center along the edges of plywood (where the panels meet the joists) and 12 inches on center in the field (across the interior of the panel). A common recommendation is to use 8d ring shank or screw shank nails, spaced 6 inches apart on the edges and 12 inches in the field. We are on hands and knees fastening with screws into the framing members at the same rates listed for nailing. Nail guns have their place, but not on the roof deck. We will routinely refasten entire fields of roof deck because the original installation was done with nail guns and uncaring subcontractors. This saves the roof deck before it fails. We refasten with screws, crawling around on the deck and doing deflection testing, and refastening with exterior-rated screws fastened into the framing members. If a screw misses, you feel it, back it out, and shoot for the joist next time. Fastening with screws = Assured fastening.

Deck Deflection

While the building code is deficient and lacking in directives for minimal deck deflection, the sub-floor spec. is .045 on a 16-inch span (which is the code for floor joist spacing). Now with fiberglass, we want to exceed this so that our very hard membrane is attached to a stable substrate. While the ‘roof-only’ specs. will hold a roof; a single-layer plywood roof deck will not hold up to foot traffic. With some PVC manufacturers, there is no directive for a 2-layer plywood substrate. As soon as a contractor contemplates short-changing the substrate to save money on a roof deck, a bad road has been taken. Softer, more malleable membranes (like TPO & PVC) will take the movement and stretching for a while, but as the membrane cures and dries, the stress can cause problems. Don’t compromise on the build because the structure must be stable and hold the deck & thereby protect the property.

SINGLE LAYER CONDITIONS

First: Check to see if you have the two layers of plywood required. Then check to see that your contractor is providing a two-layered roof deck construction. Think: If a ‘roof only’ single layered construction will not hold foot traffic, how is a pedestal system along with pavers going to improve anything? The tiles or pavers add load and the pedestals increase the intensity of the load of the walkways and the people walking around atop the paved or tiled walkways. This is an important thing to consider: How do you add load and lessen the distribution of total load to the pinpoints of the pedestal system without compromising the deck itself? You don’t. Build the deck with two layers of plywood and then you can permanently clad the deck.

Check the Specs!

There are PVC deck membrane manufacturers specifying single layered builds. What this means is that the substrate will deflect and the roof membrane will take the stress. PVC is much more malleable than fiberglass, but do you compromise on the build only to lay the increased stress on the waterproofing membrane above? We think not and as mentioned for the ‘roof only’ applications of TPO, EPDM and others? There are access systems for the occasional traffic related to utilities and air conditioner services on large commercial rooftops, but the builds are steel, not plywood and the traffic is rarely needed, unlike a roof deck where the traffic is more frequent. Just build a solid deck and clad it with the toughest membrane attainable – Fiberglass!