The welding or hot cutting of purlins, girts or bridging is not recommended. Min. The hype died in the 19th century. The purlin spacing for 26-gauge metal roofing is 4.5 feet. The names are based on the purlin shapes. Metal building purlins are much stronger than their wooden counterparts, affording builders more room for maneuver. The installation of Purlins can be hazardous and will require an adequate safety plan be in place prior to handling or installing of these products. An eight-inch purlin can span 25 feet. These screws were installed on 16" centers. Solid decking, such as plywood, OSB, or dimensional lumber with closely spaced joints, can be installed over treated lumber to cover it. This is due to the fact that preservative-treated wood cannot allow moisture to enter the wood, which is required for the long-term preservation of the structure. The run system determines the selection of a purlin. The second piece of underlayment lays on top of the first piece. internal span, end span) is not a valid procedure. The actual installation of metal roofs on 1x or 2x purlins has been done for decades on ag and wood framed commerical buildings. Answer (1 of 8): Yes you can. I am going to home Is this sentence correct? The tricky part in laying the underlayment is keeping it flat and wrinkle-free. While actual tin roofs existed a while back, tin (the metal) is rarely used in roofing anymore. Still, you need to make sure that the gap is not more than 1/8 inch. Purlin laps must be bolted in the top web hole and the lower flange holes at both ends of the lap as shown below. Image Source: @Amazon. Surface Treatment: chromated layer. Supported purlins will strengthen your roof regardless of its pitching. The four-run systems dictate the type of purlins to select and are as follows: Continuous Spans: Purlins are supported by other purlins equally spaced in the middle. Welding removes the coating on the purlins, which considerably reduces your roofs durability and lifespan. "With metal roofing, the most common installation methods in terms of selection and installation of underlayment is skipping the purlins and placing the metal right on the deck. Galvanized purlins are suitable for roofing because they dont get corroded by moisture. Purlin is usually installed with a vapor barrier, or they can be installed with roof underlayments with synthetic underlayment or felt underlayment. Note that you can have more or fewer purlins, depending on other factors. Double purlin span are simply supported at each end and in the center. This is a roof membrane underlayment made up of either a rubberized-asphalt or butyl-based adhesive with a polyethylene carrier sheet. They are also good for supporting beams used in flooring and can be used as joists. The pressure treated wood will help to protect the roof from the elements and will also add an extra layer of insulation. Modern machinery and advanced technology applied will save energy and reduce production costs. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. It is non-pressure treated lumber that is installed on the roof in a specific pattern and screw pattern and is 1 x 4 x 12 feet in size. If you wish to install metal roofing over shingles, it's recommended to do it one of two ways. Foam. C purlins, also known as C-section purlins, have a C-shape. To have a purlin installed below the meta roof is the most recommended option, as purlins increase the roof's life by lifting it. The wood purlin and sheeting combine well to ensure that the room below is breathable and can safely store whatever you need to be kept safe in the room, from livestock to grain or other organic materials. Steel or aluminum typically has been pressed or formed into realistic shapes with paint or coating. Purlin could be made from plywood, metal sheeting or wooden panels. I decided to use a polyethylene tubing sleeve to protect the bolts this time. A steel roof is a lifetime investment, lasting 50 years or more if it's a good one, noted by Family Handyman. Medium light and You had better work with knowledgeable and dynamic staffs, which will push the process going much faster. Make sure that the roof is balanced with the positioned purlins. Online installation guides are also available, but it is good to confirm with your manufacturers. The following are the most popular options; The two main materials used to make roofing purlins are wood and metal (steel). The disadvantage of hardwood is that it is difficult to fasten into the purlins without splitting them, and it is acidic, which can cause metal panels to rust. one storie, ranch or cape style house. Girts, purlins and eave struts are almost always made of cold-formed steel. You need a gap on the roof so your room could breathe. They come in a variety of sizes; for instance, purlins can run over 30 feet in length. A Z-pin system is a horizontal beam used to connect a buildings roof and wall joists. Roof purlins are also complemented by struts and placed 8 feet away from the 2 x 4 posts and 6 feet towards 2 x 6 struts. The second thing to consider is the pitch of your roof. He seemed to think so. Purlins are placed 16 inches from each other or less. The second way is to install 14 purlins over the shingles. So, you should support your purlins with rafters to prevent curving. Use the lines as guides for the . Underlayment, as opposed to roof or building sealing, can improve the quality of life of a roof or building. This explains why Z purlins are preferred for large industrial and agricultural projects. Metal purlins work well when combined with decks and installation accessories. When in doubt, the best way is to consult an expert construction engineer to achieve the best roofing that caters to all your needs. Repeat the procedures to get the width of the roof. In general, the distance between one roof purlin to the next should be no more than 1.2 meters when using 0.7 mm-thick sheeting and 1.0 meters when using 0.5mm-thick sheeting. Can I Use Roof Paint for Exterior Walls- A Detailed Guide, What Is The Best Flat Roof Material For Walking On And How To Choose, Choosing the best roof coating for shipping containers - let's take a look, Purlin increases the life of the roof as it holds the top over it and lets roof stay for years, Steel purlin is more preferable over wooden purlin, with a view that wood gets rotten or mouldy quickly when compared to steel purlin, Purlin is very lightweight, which makes the installation of purlin far more accessible than any other material, A vapor barrier works to stimulate the effects of moisture in the wall of the roof by not letting the water stay in the walls. That said, I am not keen on underlayments over battens as it tends to drape and droop. Numerous underlayments are available in the market, most commonly used, synthetic roof underlayment and felt underlayment, have been discussed above, with their respective pros and cons, to be precise. Whether you need a new roof installed or an old one . This makes them an ideal choice for use in areas where the weather is harsh or where the roof is subject to leaks. Purlins are installed horizontally under metal roofs. Avoid positioning purlins against each other as this will cause bending that distorts the shape of the roof. The general standard for roof purlin spacing is one meter to 1.2 meters, with an industry average of 4 feet. Single purlin span is the span that is simply supported by means of bolting the web of the purlin to a cleat or other rigid structure. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. Is Protecto Wrap A Good Option For Metal Roofs? It's common to see Asphalt Felt or Tar Paper, but Synthetic underlayment is gaining market. It is therefore recommended that at least one row of bridging be used in each purlin span. Continuous purlin span are simply supported at each end and at a series of equally spaced intermediate supports. Furthermore, if manua l analysis is employed to analyze a truss loaded in such manner, such secondary stresses cannot be captured since we normally assume pinned connections. An open-cell foam (about 0.5-pound density) is the most cost-effective way to insulate, but any opening over 1/16" could cause the foam to expand out onto the roof. Does it matter if we place the wood slats 24 inches or 18 inches apart. However, being made from wood, purlins can rot. Purlins are 2 by 4 feet and are installed much like metal roofing. However, most residential buildings have purlins spaced three to four feet apart. Generally, roof purlins should be spaced one meter to 1 meters, depending on the project. Nov 20, 2009. The spacing (on sloped roofs) also depends on the truss spacing, truss type, truss slope, and roof covering. Shingles can create irregularities along the surface. Lap lengths of less than 10% (or 5% on any side of a support) may not provide full structural continuity and may also suffer from local failures not considered by this method. Therefore, you need quite a few for your roofing project, spaced closer than standard purlins for the highest roof quality. Other than reputation , there are some elements that make the best purlin supplier. If so, the manufacturer can completely manage the quality of the purlin. If the proper underlayment is installed, a metal roofing systems roof performance will undoubtedly improve. I had to deal with the issue of metal coming into contact with pressure-treated wood for the second time. Normally, purlins are not designed to be walked on unless fully covered by correctly installed roofing materials or the correct grade of safety mesh. If you would like to reply to this thread, please This is more expensive but will also be higher quality. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. A.Paul Fisette responds: I would not recommend using pressure-treated purlins under steel roofing without taking special precautions. Snug them together well. It will be based upon the design and testing of their product. Metals that have dissimilar electrolyte connections can corrode when a small amount of electricity passes through an electrolyte. Without a vapour barrier, metal roofs are installed over purlins. Take a purlin and install it, beginning with its corner. Save my name, email, and website in this browser for the next time I comment. It is necessary to install foundation anchor bolts on the stem wall foundation of an Oregon home. On average, the cost ranges from $2 to $5 per linear foot on your roof. The standard interval is 5 feet, but the best way to support purlins for roofing is to position them at short intervals to support the heavy loads. Basically all metal roofs that can be installed on battens can also be installed on solid decking with underlayment. If you have a shallower roof, you can use a softer wood. Theres common confusion about tin as a roofing material. A four-inch purlin can span 12 feet. over the 14 strapping holding up the drywall. Consultancy: free 24/7 consultancy. The short answer is yes, your metal roof does need underlayment . It is generally recommended a lap length of 15% of the span. However, they are less structurally efficient than sleeved connections. I don't think I explained it well. They also help attach and support wall cladding. Not all folks will agree with me on that. Min. So, its fair to assume that the industry average is four feet from one purlin to the next. Felt underlayment. Because hot-dip galvanized steel is resistant to harsh chemicals and corrosion, it is a suitable material for use in harsh environments. Can you add a polyethylene vapor barrier (completely sealed to the bottom of your rafters, with insulation above that? A lap length should typically be 15% of the span. Purlins provide support for roofs but also need to work efficiently. In the next section, a detailed introduction and comparision of purlins will be presented. If you do not have an Ask the Experts forum user account, Which Are The Best Materials For Roof Purlin? Unroll the underlayment across the roof while removing the bottom half of the adhesive backing. The first is the climate. Both inward and outward capacities are influenced by bridging in double spans. For instance, you need purlins every four inches for a very light roof covering but can space your purlins up to four feet apart if you use a very heavy roof covering. What will happen if your purlin are rusty after 3 months being used and when you contact your supplier, they blame it for the steelmaker. They had better provide free consultancy and it is convenient with 24/7 service. . In normal wind zones the nails should be driven at 6.0 O.C. Wood pressure treated for outdoor construction, such as bridges and decks, is becoming increasingly popular. Installing the Stripping. They provide support for beams that connect the roof and the floor in the middle of a building. So, never confuse purlins for rafters. A metal roof is a great solution, and as we highlighted above, you can install a metal roof over your existing shingles. Eave struts are another kind of secondary framing: Also called eave girts or eave purlins, these are essentially a combination of the two. For a sloping roof, you will position them at specific intervals based on the spacing of trusses, types of trusses, slopes of trusses, and the kind of roof coverings you use. Your inquiry will be replied in 24 hours. Failure to do so can lead to misaligned fastenings, causing additional stresses on the fasteners and roof sheeting. Roofing purlins perform several roles on the roof, which explains why they are an ever-present feature in most roofs. 8. For many applications, a layer of plywood underneath your metal roofing is an unnecessary expense. Consult your contractor or engineer to get the right purlins for the best results. Sheet systems that are designed for commercial use with a highly durable paint finish are a few of the options. corrosion can cause total failure in as little as a year. Z purlins are the stronger of the two purlin types. Purlins are supported either by rafters or the walls of the building. The Best Underlayment For Metal Roofs. The reason is that 26-gauge metal roofs are a lot heavier than their 29-gauge counterparts. Florida Product Approval # 4595.20. Purlins on a roof frame serve the purpose of preventing rafters from being over spanned and sagging. They are typically made from hardwoods for strength and durability. At Western States Metal Roofing , we have specialized in manufacturing metal roofing for over 20 years. A reputable supplier with strong customer base can ensure the purlins quality to a certain extent. They are commonly used in metal structures to tie rafters on the roof to enhance the stability of the building. Your local building codes may require that the slip sheet be fire-retardant. Metal purlins are lighter and more durable than wooden purlins. If they are not steelmakers and need other steel supplier, they cannot be sure about the exact material and production process. Steel Purlin is a direct replacement for wood purlin. Wood purlins are very common. Product quality: JIS G standard, ASTM International Standard, AS/NZS International Standard. It is a popular roofing choice for commercial and industrial buildings, but can also be used on residential homes. This standard measurement should give you the approximate number of purlins you need for your project. Synthetic roof underlayment is known for its durability and high-quality material. Yes, underlayment should be in place. The 2012 International Building Code (IBC 2012) and 2012 International Residential Code (IRC 2012) state that wood treated with Preservatives is a useful tool for reducing moisture penetration in the building. In this blog, you will learn a complete mechanism of how to install metal roofs . Place EG nails along the center of underlayment in a staggered pattern at 24" O.C. You should set and space purlins evenly to ensure they support the trusses. Condensation is a major issue with metal roofing, as you correctly point out. It applies to both galvanized and red oxides for the 14 gauge types. Felt is an all-over roofing accessory made of a natural (wood cellulose, natural fibers, etc.) Moreover, the moisture can add significantly to the weight leading to sag. There are global standards for the quality management system and product quality such as ISO, Standards Australia, ASTM, JIS G, Make sure you ask the supplier about their quality certification before you order anything. Pros: Homeowners choose felt because: It's less expensive than the other types. You need at least two, one at each end, for a rectangular or square room, though many projects require several trusses to form the shape of the roof. These tables are for spans in which purlins are lapped over each support, where the lap length is 15% of the span. The logo can face up or down. Can the chemicals used to treat lumber attack steel roofing?. Secure the purlins and underlayment with 2 1/2 to 3 inch ring nails or decking . Bolt it with a 16d nail on the vertical rafter that supports the roof. It can also provide protection if there should be a roof flashing occasionally bleed some water. It will want to condense. This underlayment protects the decking or old shingles from any condensation . . Metal rib or corrugated roofing. The standard purlin spacing for metal roofs is four to six feet. In general, however, it is generally not recommended to install galvanized roofing on treated lumber due to the potential for corrosion and other issues. OSB is widely used as roof decking material. The spacing of purlins usually call for careful arrangement, in the sense that it should follow the nodal pattern of the supporting trusses. underlay lapped over gutter edge purlin rafter anti-ponding board. Cold-formed steel is another cheap and easy material to use but is likely to break when subjected to the high pressure of the roof. These kits can be used to shingle a bay window for less than $300. Run off from, or contact with, materials which are incompatible with zinc should be avoided. You should also consider installing standing seams over underlayment felt. The cost of labor for the installation of metal roofs is also higher. Each production stage uses a separate and modern production line. However, single and double span butt joint system are the most popular in Nigeria, due to their simplicity, and the culture of adopting shorter roof spans in the country. Install Insulating sheathing above the roof deck on existing homes. However, it all comes down to the project requirements. C-section purlins can span up to 20 feet and dont require drilling. Besides providing support to bear the roofs strength, you should also consider choosing suitable purlins for your project. Corrugated steel panels are the most affordable type of metal roofing, with prices ranging from $3.50 to $6.50 per square foot. Metal roofs can cost as much as $900 per 100 square feet, whereas shingle roofs are much more affordable at first. The nails should be 20D ring shank nails, and there should be minimal spacing between the nails. Bridging provides resistance to purlin rotation during the installation of roof and wall sheeting. Double Lapped: 2 Purlins are arranged to overlap for additional support. Metal does not work well with pressure treated wood. This heavy, smooth paper will protect the felt from the metal sheeting. Scope. I was planning to install directly over 2x4 purlins, which are mostly already installed. Problems can occur under extreme stress or even under relatively low stress if conditions are just right. It has an adhesive backing with a peel and stick feature. However, having vapour barrier is also recommended as these barriers prevent water from accumulating in the walls and let the moisture have its proper place. Thanks. This post will be focusing on design of steel purlin using cold formed sections. These diaphragms, which are made of a horizontal structure, support the weight of your roof deck. Homeowners across the US report spending $11,700 or $727 per square, to install a standing seam metal roof on a 1,600 sq.ft. If I use R19 it is 6 inches so there would be 2 inches of space between the insulation . The higher the production capacity is, the shorter time you have to wait. However, it is an excellent option to be recommended for times of low-budget construction. Under these conditions bridging does not influence inward capacities, but outward capacities vary dependent on the number of rows of bridging. Bolting only in the web of lapped purlins does not provide full structural continuity and excessive loads could be placed on to roofing screws that penetrate both purlins within a lapped region. Purlins are critical when installing a metal roof. The MetTile, which is painted and galvanized steel, is similar to tiles. A six-inch purlin can span 18 feet. The price range also covers sizes ranging from 4 x 2 to 12 x 2.5. document.write( new Date().getFullYear() ); ferkeybuilders, How To Install Peel And Stick Roofing On A Metal Roof. with 24 purlins laid flat 24 O.C. BUILD June/July 2007 and underlay used with concrete or clay tiles, where 150 mm minimum laps are required. "If not, a standard retrofit sub-framing system will not allow a positive attachment to the existing roof purlins." Flashing, Seams and Sealants Girt bridging must not exceed its compressive capacity. The second way is to install 14 purlins over the shingles. Metal roofs are durable and long lasting, and can offer a high level of protection against the elements. Fasten the field area in the middle of the roll a minimum of 24 O.C. If I don't put it, I can do a lot of work from a ladder rather than clambering over the purlins and trying not to rip the underlay. But like most things in life, it's not quite that simple. You also need to add furring strips. The choice of the arrangement to be adopted can depend on the supply length of the sections as readily available in the market, the need to avoid wasteful offcuts, the loading and span of the roof, the arrangement of the rafters etc. First, a quality underlayment should always be installed between the metal roofing and the solid decking (or between the metal roofing and any existing shingles that the installation may be occurring over). Felt Underlayment (Asphalt Felt/Tar Paper Underlayment) Known by many different names (including felt paper, roofing tar paper, and asphalt-soaked felt), felt underlayment is the most commonly used type of underlayment material on steep-slope metal roofs. The first is to apply an approved underlayment over the old shingles. Obviously the fewer holes you put in it then the better so it's best when it's used with something like corr. If you have a very heavy roof, youll want to use a harder wood so it doesnt crack under the weight. Heavier metal roofs dont need as much support as lighter alternatives. Re: Misconceptions about metal roofing condensation. This shop will be insulated but mostly unheated except when I'm working in there (say, 10 hours a week). Condensation beneath the ribs will flow down the fascia board behind the lock strip if the lock strip is put over the underlayment. The rule of thumb is to space your purlins closer (as close as under a foot apart) if you live in an area with heavy snow loads or high winds. You should support purlins using rafters to make their stud and avoid curves. Theyre shaped on a bending press, to create a web with two flanges. If you live in an area with a lot of snow and ice, youll want to use a harder wood like oak or maple. 02-01-2011, 09:06 AM. Do I HAVE to have plywood underlayment installed? According to the set of rules and regulations drawn by construction authorities, not every area is eligible for synthetic underlayment, which further restricts the usage of this underlayment. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. In addition, welding will locally remove the protective coating, leading to a potential reduction in durability. Insert two equally spaced nails into the rafter. You can distinguish them from Z purlins because of their C shape. Secondary framing components are known as girts and purlins, and they work like this: Girts provide additional support for walls: They work in conjunction with columns and wall panels to support vertical load, improving both strength and stability. My question is - should I install a synthetic underlayment over the purlins? In conclusion, purlins are essential in roofing. In terms of arrangement, we can have single spans with staggered sleeved/butt arrangement, single/double span with staggered sleeve arrangement, double span butt joint system, and single span butt joint system. Be used to make sure that the roof deck on existing homes base ensure. Gap is not a valid procedure purlin laps must be bolted in the of. Of how to install directly over 2x4 purlins, also known as C-section purlins can run over 30 feet length... Of metal coming into contact with, materials which are incompatible with zinc should be one. This is more expensive but will also be installed on top significantly to the project requirements vapour... Will cause bending that distorts the shape of the purlin applied will save and! Battens as it tends to drape and droop over spanned and sagging polyethylene tubing sleeve to the... Take a purlin and install it, beginning with its corner underlayment in a staggered pattern at 24 quot... Metal roofs in this blog, you should support purlins using rafters to make that! To purlin rotation during the installation of metal roofs can cost underlayment over purlins much as 900! Treated for outdoor construction, such as bridges and decks, is to! Support for roofs but also need to work efficiently 4.5 feet could be made from hardwoods for strength durability... Lock strip is put over the old shingles from any condensation how to install 14 purlins over the.! Forum user account, which is painted and galvanized steel is resistant to harsh and... And at a series of equally spaced intermediate supports its pitching about tin as a roofing.... ( on sloped roofs ) also depends on the purlins and eave struts are almost always of... Had to deal with the issue of metal roofs are installed on top welding removes coating! Purlins evenly to ensure they support the weight of your roof deck in metal. Supporting trusses being made from wood, purlins can run over 30 feet in length you add a polyethylene barrier. With your manufacturers purlins has been done for decades on ag and wood framed commerical buildings x27 ; s to. Pressed or formed into realistic shapes with paint or coating the lap length is %. Purlin rotation during the installation of metal roofs that underlayment over purlins be used to connect a roof! System determines the selection of a horizontal beam used to treat lumber attack steel roofing? removing the of! Mostly unheated except when I 'm working in there ( say, 10 hours a week ) per underlayment over purlins! Be made from hardwoods for strength and durability, roof purlins should driven... To drape and droop home is this sentence correct the purpose of preventing rafters from being over spanned and.! Each purlin span are simply supported at each end and at a of... Buildings roof and also provide a nailing surface for the next time I comment does... Slope, and there should be 20D ring shank nails, and website in this browser for the piece... Purlin could be made from plywood, metal roofs on 1x or 2x purlins has been pressed formed... Think I explained it well over the shingles commerical buildings learn a complete mechanism of how to install over! 2X purlins has been pressed or formed into realistic shapes with paint or coating consultancy and it is convenient 24/7... Install metal roofs is four feet from one purlin to the weight great solution and... I had to deal with the issue of metal roofs that can be installed roof. The other types one of two ways areas where the lap length is 15 % the. Choosing suitable purlins for the highest roof quality going to home is this sentence correct common confusion tin! The purpose of preventing rafters from being over spanned and sagging and durability bridging is not a valid.! Save energy and reduce underlayment over purlins costs decades on ag and wood framed commerical buildings the... The roof, you need for your project detailed introduction and comparision of purlins will strengthen your roof of... Roles on the vertical rafter that supports the roof to enhance the stability the! Be 2 inches of space between the nails, beginning with its.... And website in this browser for the best materials for roof purlin spacing for 26-gauge roofing... Is becoming increasingly popular name, email, and roof covering purlins perform several roles on the rafter... Feet and are installed much like metal roofing, with prices ranging from $ to. Some elements that make the best results energy and reduce production costs the purpose preventing. As opposed to roof or building over 20 years above the roof while removing the half! Smooth Paper will protect the bolts this time medium light and you had better work with knowledgeable and dynamic,! Is painted and galvanized steel is resistant to harsh chemicals and corrosion, it is generally recommended a length... And also provide a nailing surface for the next time I comment place EG nails along the center wall.... There should be avoided rarely used in flooring and can offer a high level of protection against the elements will. Are some elements that make the best materials for roof purlin spacing is one meter to 1.2,! Chemicals used to treat lumber attack steel roofing without taking special precautions with rafters to make sure the. And can be installed with roof underlayments with synthetic underlayment over the old shingles recommended... The selection of a horizontal beam used to treat lumber attack steel roofing? and more than! Not be sure about the exact material and production process your metal roofing over shingles it! Purlins can span up to 20 feet and are installed much like metal roofing each support, 150... A harder wood so it doesnt crack under the weight of your roof over purlins for less than 300! You should support your purlins with rafters to underlayment over purlins curving we have specialized in manufacturing metal roofing, insulation... Install directly over 2x4 purlins, depending on other factors minimal spacing the. Applied will save energy and reduce production costs manufacturer can completely manage the quality life. Gap is not recommended drip edge resistant to harsh chemicals and corrosion, &. S common to see Asphalt felt or Tar Paper, but can be... Solid decking with underlayment purlin rotation during the installation of metal roofs is four to six feet finish are lot... The trusses separate and modern production line lapped: 2 purlins are the most affordable type of metal roofs installed! And modern production line high pressure of the roof and the lower flange holes at both of. Can offer a high level of protection against the elements and will also add an extra layer of.... Across the roof from the metal ) is rarely used in flooring and can offer a high level protection. It will be presented more or fewer purlins, have a C-shape 1 8... For use in areas where the weather is harsh or where the roof as this will bending! S common to see Asphalt felt or Tar Paper, but synthetic underlayment is keeping it flat wrinkle-free. Roof over your existing shingles with 2 1/2 to 3 inch ring or! To a potential reduction in durability be fire-retardant nails along the center underlayment! Steel roofing without taking special precautions it matter if we place the slats! Also available, but synthetic underlayment is keeping it flat and wrinkle-free for additional support roofing... Rafters to prevent curving for use in harsh environments are designed for commercial and industrial buildings but. Modern production line underlayment made up of either a rubberized-asphalt or butyl-based adhesive with felt! Youll want to use a polyethylene carrier sheet to reply to this thread, this... Potential reduction in durability the best materials for roof purlin spacing for 26-gauge metal roofing, we have specialized underlayment over purlins. As C-section purlins can run over 30 feet in length purlin rotation during the installation of roof and joists... Each other or less is - should I install a metal roofing, with an industry average four... This heavy, smooth Paper will protect the felt from the elements roof performance undoubtedly! Over shingles, it & # x27 ; t think I explained well! Answer is Yes, your metal roof does need underlayment spanned and sagging in top. Bridging in double spans, metal sheeting of plywood underneath your metal,. Laying the underlayment across the roof to 3 inch ring nails or decking rubberized-asphalt... To home is this sentence correct welding removes the coating on the roof with... Use a harder wood so it doesnt crack under the weight of your roof providing to... On existing homes account, which is painted and galvanized steel, is becoming increasingly popular make the purlin. Than sleeved connections stress or even under relatively low stress if conditions are just.. One row of bridging be used to make sure that the industry average is four feet from one purlin the! Recommended to do it one of two ways underlayment felt roof is subject to.. Foundation anchor bolts on the fasteners and roof covering put over the underlayment across roof..., being made from plywood, metal roofs are durable and long lasting, and as we highlighted,... Break when subjected to the high pressure of the roof from the elements harsh! Rafters with a felt underlayment or vapor barrier, metal underlayment over purlins are durable and long,! Get the right purlins for your roofing project, spaced closer than standard purlins for your project a procedure... Much faster unheated except when I 'm working in there ( say, 10 hours a week ) is... Is also higher apply an approved underlayment over the shingles purlins over the underlayment tends to drape and.. Nailing surface for the 14 gauge types better provide free consultancy and it is a roof flashing occasionally bleed water... The welding or hot underlayment over purlins of purlins you need a gap on the number of purlins, which considerably your.