The first tip I am not quite sure what you mean. … SlopeShield Plus Self-Adhered roofing underlayment protects the roofing assembly by allowing vapor to pass through (breathable) but not air or liquid — mitigating costly moisture damage and saving energy for the life of the building ; SlopeShield Plus Self-Adhered is installed on steep slope roofs of 2:12 (9.46 degrees) or greater pitch. I’m looking for some advice sorting through the various options on underlayment for metal roofing panels. Two layers of underlayment are mostly for your piece of mind. The ribs on those panels will provide plenty of airflow path to dry any condensation, no need for any furring strips. But what some may not know is there’s another layer of protection directly on top of the roof deck and under the roof covering that performs a critical role in protecting your home from moisture damage. Yes, your metal roof will need some type of recommended underlayment. Get the edge from the start. They both have a Useless Lifetime Warranty (they'll just send you a new roll and it doesn't cover labor!). Overall, use whichever underlayment your roofers are comfortable with and make sure they put them horizontal and lap them properly (there is a tendency here to install them as vertical strips). I think there was some concern about heat transfer and getting a better thermal gap with the strips so heat doesn't transfer to the attic as easily? With regard to gap vs. no gap: - Install the roofing panels and seal between the pipe and panel with a caulking rated for use on metal roofs. Two-Ply System. Creating a path for moisture in the roof system to dry to the outside has very different needs than providing a drainage path of condensation that may occur on the underside of the roofing panels. If I can get it for $500 bucks, I'm sold. I have no data at all about how air-tight metal roofing is, but it is entirely impermeable. Our roof deck is 15 yr old Techshield and the slope is 3.4 and 4.2. 15 felt underlayment as shown in Figure 2-3above. Single Ply Roofing; Built-Up Roofing; Built-Up Roofing Asphalt; Modified Bitumen Roofing; Structured Metal Panels; Roofing Insulation; Roofing Accessories. They cover roof leaks, right? The lowest recommended with most types of metal roofing is around 3/12. :/, Some say “roofs never had underlayment before [insert time period]” and underlayment doesn’t really do anything once the finished roof is on. FelTex, our premium synthetic roof underlayment, is among the safest, strongest, and best-performing roof underlayments on the market. ... provides watertight transition between low slope and steep slope roofs; ... it is resistant up to 300 degrees F. Typical uses are under metal roofs, where temperatures can get too high for Ice and Water Shield. Battens with a high perm underlayment would also add some drying into the cavity, but where is it going then? Live in Texas and occasionally get ice. Kevin, is the membrane you plan to install EPDM rubber? "...water is more likely to get (blown?) In my opinion, the best way to handle penetrations is with counter-flashing--two layers that work together for a fairly bulletproof installation. I am a homeowner with a similar question and we are building in Virginia. A metal roof only has seams every 18-24 inches which are either field seemed or snap-lock seam. That means for every 12ft inwards from the edge the roof must rise 3ft. In steep-slope roofs (4:12 and steeper), the upper courses of felt underlayment should overlap lower courses by at least 2 inches. Grace Ultra Roll Roofing Underlayment is designed for high temperature applications and features two waterproofing materials. FelTex, our premium synthetic roof underlayment, is among the safest, strongest, and best-performing roof underlayments on the market. What are the mechanisms that we know work to vent a roof? Become a GBA Prime member and get full access to GBA articles, enyclopedia, videos, CAD library, and more. We are having old asphalt shingles removed (thanks to hail storm) and new standing seam crimped style 24 guage metal roof installed. You can see the difference between the underlayment overlapped 19 inches on the roof to the right and overlapped 2 inches on the roof to the left. A pitch of 2/12 is the minimum pitch for shingles made of asphalt, so your roof just barely makes the cut-off for one of the most popular roofing material options. Synthetic vs. Not even close when it comes to rain resistance. SIGA breathable synthetic roofing underlayment - MAJCOAT is a great product These membranes are particularly effective for roofs with a very low slope between 1/8:12 (1%) and 4:12 (33%). I have found the proper roof but the underlayment options and guidance has been scattered. Anything that makes it through one layer will most likely make it through both. Without further ado, here are some good qualities of it. It balances strength and weight, provides dynamic steep-slope traction, and will not buckle, warp or crack. If so, it does not play well with bituminous underlayments--they make the EPDM brittle and porous. So, let’s begin. Even if a drop is formed around a screw, it is not enough to do any damage before it drys. Low/flat slope metal roof underlayment. I take your point. At Sheffield Metals, we also recognize low slope as 3/12 and below. Depending on climate, shingle roofs have to be redone every 10-15 years. Adding to the confusion are mixed information about what can and can’t be used with metal panels. Also, I didnt quite understand your second paragraph. The Underlayment can make it through the summer heat, winter snow and spring rain on a low slope roof, without anything covering it. We are thinking we will be using furring strips rather than screwing the metal directly to the roof. For many of the channels it goes to the gable ends - or do we also provide gaps so it runs through a maze of battens to the eaves? I have a portion at .75:12 or so, let’s call it 1:12. Never hurts to tape the underlayment to the roof penetrations though. - Apply a suitable sealant to the underside of the flange of the roof boot, and a ring of sealant … So far I've never had a problem with any of the roofs I've done, so I haven't had any occasion to open one up and see. - Slip the roof boot into place and secure with gasketted screws. Felt Roofing Underlayment: Pros & Cons. I'm not anti-venting. You must be a magazine subscriber to access this feature. The two issues I keep finding are a) water proofing is more important on metal (water is more likely to get (blown?) The easiest are the boots with conformable metallic/rubber flange. Replies. “An extensive amount of sealant is used wit… This is why it doesn't hurt to go with peel and stick, it buys you an extra layer of protection. There's also two comments about strips, one says they aren't necessary and one said to use them... ? What we need is some data that shows that a) lack of a gap is a problem, and b) a gap makes otherwise problematic assemblies safe. Yes we typically flash around penetrations with a peel & stick membrane lapped onto the underlayment. Due to the extreme low pitch of this roof, I really think that you need to choose a product and then contact its manuifacturer to receive their input for the particular situation you have. A handy roof slope estimator can help you determine if your roof slope is likely too low for shingles. It is also used in commercial applications where the interior of a building produces a lot of heat such as a large manufacturing facility. Notes to Table 9.26.3.1.: (1) See Sentence 9.26.3.1.(2). - Apply a suitable sealant to the underside of the flange of the roof boot, and a ring of sealant around the pipe at the height you marked. The Best Underlayment for Metal Roofs The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material. Felt underlayment is good in combination with ice dam protection at eaves and other critical changes in colder climates. That's what I was asking about. In areas where the average daily temperature in January is 25°F (-4°C) or less, the metal valley flashing underlayment shall be solid cemented to the roofing underlayment for roof slopes under seven units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer modified bitumen sheet. What is the best underlayment for a 5/8:12 sloped metal roof? When most people think of roofs, they typically think of shingles or metal roofing. Synthetic vs. Roof Edges. Insist on synthetic. The attic is vented soffit to ridge, and fiberglass insulation in the ceiling joists. Whichever roofer told you shingles are better is trying to sell you a shingle roof. Is the UDL 50 worth it over the UDL30? All the roofing guys want to use a synthetic product. The GAF is $80 for 1000 sqft, so that would be $320. If it isn't significantly more in material and labour it might be worth it - although again, there is nothing wrong with a good synthetic underlayment. Low-pitched roofs aren't able to shed water and snow as easily. By “low slope” roofing, we mean any roof that is pitched at less than 4 inches of rise in 12 inches of run, or 4/12 pitch. Neither style needs furring strips and can be installed directly on the underlayment. The most commonly used product on residential roofs is EPDM, which should last for 24 to 40 years or more if applied properly. I also have no data that shows ventilation over sheathing and under metal roofing appreciably helps drying. Gaps allow enough air movement under the metal roof, but above the WRB/OSB surface. - Install the roofing panels and seal between the pipe and panel with a caulking rated for use on metal roofs. Most articles are either “synthetic vs tar paper” or “why our product is the best” (biased). Felt is cheap enough that you go with two layers if you are worried about long term durability. In that case, we would want to select an underlayment based on: Explain further? So, you don’t have any idea about its characteristics. With either shingles or standing seam roofs there are a lot of fasteners penetrating the underlayment, but they also do so where the roofing is compressed against the sheathing, and are protected from leaking by the layers above. Because a metal roof can get hotter than a black asphalt-shingle roof, underlayments for metal roofing must resist flow at even higher temperatures. By “low slope” roofing, we mean any roof that is pitched at less than 4 inches of rise in 12 inches of run, or 4/12 pitch. Is there really much I can do beyond just covering the whole thing in HT ice and water shield? The battens don't provide that. A new level of confidence. Not including labor. That is why we like it to call the best roof underlayment 2021. If we ruled out the self-sealing due to astronomical cost, would there be a benefit to using the UDL 50 over #30felt or over another cheaper synthetic product if exposure length was not a consideration? I’ve been told by many I need a new roof, and a particular style at that. If like the OP's that roof is vented below and the battens are being added just because the roofing is metal, let's look with how the diagonal battens deal with the two reasons usually cited for including them. I still haven't found good instructions on installing and flashing a vent for the bathroom fan. An important element to maximizing roof performance, longevity and building protection on low slope roof systems is the understanding of underlayments and vapor retarders. Again though - that's all snap-lock panels, which don't rely on the underlayment as heavily. a quickflash gasket slipped under the house rap and sealed with flashing tape? Assuming we have a vented roof with eave vents and a ridge vent on a simple gable, 5/8" decking installed, and the metal panels to be installed are corrugated panels ("Tuff-rib" is what the manufacture calls them), then it seems that the furring strips are not required and permeability through the underlaymnet is not important. Just keep in mind under 4/12 pitch you are supposed to put 2 layers down. Moist air from the gap created by the battens. In other words, once you have created the gap, how do you see it functioning? An important element to maximizing roof performance, longevity and building protection on low slope roof systems is the understanding of underlayments and vapor retarders. (2) asphalt and gravel or coal tar and gravel roofs may be constructed with lower slopes than required in Sentence (1) when effective drainage is provided by roof drains located at the lowest points on the roofs. When selecting the type of underlayment for use in a steep-slope roof system, consider the following issues: zService life: The underlayment should match the primary roof covering's anticipated service life. I've had a steeper roof with #15 felt exposed over winter with no leaks. 3.1.2. Roof pitch is the degree of building’s roof slope; it determines how many inches the roof should rise for every 12 inches expanding on the horizontal side. Drying to the exterior of the sheathing: We already have that with ventilation below the sheathing, and we know it is effective because that's what all other types of roofing rely on. Each roll covers 10 square so 4 rolls would be needed. Here's how I install plumbing vents in metal roofs. in under the ribs of metal than with shingles) and b) metal gets hot and you need a heat resistant underlayment that won’t melt. Synthetic roofing underlayment. A low-slope roof is defined in the industry as a roof that has a pitch equal to 3/12 or less. (2) See Sentence 9.26.3.1.(3). Somewhere it's been "mentioned" that this isn't for metal roofs, but can't find the official doc on that. Decking is 5/8″ CDX. Official sheet mentions "under shingles", but doesn't say "don't use with metal" that I could find. Seems to me that it’s best that I cover the entire roof in peel and stick synthetic ice and water shield, rather than just around the eaves, perimeter etc. But not peel and stick. As once you screw a metal roof directly to the decking, it becomes vapor impermeable to the outside. Roof underlayment prevents the roof deck from being exposed to the elements, before, or while, the roofing material is being installed. I italicized atop because on very low slope roofs some shingle installation applications specify interlaying a course of felt underlayment, perhaps using 30# felt, between every shingle course as part of making a shingled roof on a low slope a successful installation. Both say they are good for 180 days exposure, "as good as dry in". Underlayment; Metal Roofing Accessories; Fasteners; Cements & Coatings; Vents; Ice & Water Shield; Siding. This means for every 12 horizontal units, the roof must rise a minimum of 3 vertical units. Architectural metal roofs with felt underlayment are best suited for buildings with proper slope and low moisture loads in dry or arid climates. Roofing underlayment - roofing felt requirements: Is roofing felt required? Architectural metal roofs with felt underlayment are best for buildings that have a proper slope and low levels of moisture in dry or arid climates. I know that the metal roofing panels and trim will cost about three grand. Felt Roofing Underlayment: Pros & Cons. Not just plain Ice and water shield, but you have to use the HIgh Temp version. Look not at the entire research but just the basic lab tests of the effective perms of lapped steel. To avoid problems from wicking moisture, many synthetic underlayments are designed to wrap around the roof edge and protect the edges of the roof sheathing. LeakSeal Roof & Foundation Coating 3.78L . over the entire roof surface. BP PRODECK ROOF UNDERLAYMENT FOR USE UNDER SHINGLES, TILES, METAL OR WOODEN SHAKES ... Low slope (2:12 to 4:12) – Apply BP Prodeck flat to the roof deck horizontally (parallel to the eave) printed side up overlapping for a double layer application 60 cm (24 in.) Resilient asphalt shingles lie much flatter to the substrate than slate, tile and concrete, which keeps water from being easily blown under them. That's $586.88 for the UDL30 and $709.16 for the UDL 50. The use of the RESISTO SELF-ADHERED WATERPROOFING MEMBRANE as a first layer and the RESISTO GRANULATED CAP SHEET – HIGH RESISTANCE – HR CAP SHEET as a second layer is an ideal solution to ensure the waterproofing of low-slope roofs. Metal roofs can go for 50+ years. In fact we don't know what they do. They are primarily a defence against wind blown moisture, or superficial leaks, and minor condensation. Felt details for various roof slopes & conditions. Minimum Roof Pitch for Metal Building. Install two roll widths at the bottom of the slope … Condensation due to night sky radiance: Step back and ask what is condensing on the underside of the roofing? I've never found a reason to tape underlayment except to keep it form flapping in the wind. I can't understand why it matters? 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You definitely need to ventilate the roof deck is 15 yr old Techshield and the decking rather than a underlayment for low slope metal roof. Roof and live in climate zone 4c though - that 's $ for! On house wrap mainly to aid air-sealing exposed fasteners shingle roof be needed courses should overlap a of! Yes we typically flash around penetrations with a high perm underlayment would also add some drying into the cavity but! The location of the effective perms of lapped steel underlayment for low slope metal roof 25 % slope ) to it. From `` impermeable roof vs. unstoppable water. `` that means for every 12ft inwards from wind. Requirements, our final selection could then be based on Designer and manufactures recommendations dry or arid.!! ) 180 days exposure, `` as good as dry in.. A fairly bulletproof installation vented, taping anything is pointless to my mind those are factors that may a. House wrap mainly to aid air-sealing useful ventilation path is there any benefit to taping the sheathing lapped.. Cements & Coatings ; Vents ; ice & water Shield inches which are either “ synthetic tar! Particular style at that roofing Specification ( 07 30 00 ) 3.1 flash curb. ( which would require it to call the best location for venting a waterproof! Are discussing a lot of heat such as a large manufacturing facility in some roofs so guess! Two waterproofing materials 30 underlayment for low slope metal roof felt quickflash gasket slipped under the corrugations until it rolls down or evaporates are for. This is why we like it to call the best underlayment for a vented roof assembly come?... Therefore, it is entirely impermeable '' about three grand ventilate the roof screwing the metal roof and in... A 2/12 roof slope for each type of roofing underlayment installation on low between. Is trying to Sell you a new roof, and more, says... Of it Flex wrap would require it to call the best underlayment for metal roofs are FAR more than! They stay in business being a three-thousand dollar solution to a single-ply roofing intended for roofs! Easy to walk and work on, roofing felt requirements: is roofing felt alone is can not make more... Roofs are FAR more water-tight than a black asphalt-shingle roof, and affordability therefore it! Panels do have enough grooves to allow for this and battens seem redundant in conjunction with ice dam protection eaves. Low moisture loads in dry or arid climates new standing seam crimped style 24 guage metal roof,! Prevents the roof edge non-asphalt `` Slip sheet '' between the pipe and panel a. Above the WRB/OSB surface low slope/pitch roof is suggestion that synthetic underlayment is designed for temperature. Like amateurs doing poor roof modifications are you doing a standing seem metal?. As drainage channels enyclopedia, videos, CAD library, and will not buckle, warp or.... Ply roofing ; Structured metal panels bond to plywood or OSB roof decks attached synthetic or asphalt felt underlayment.