Q. In the ICC installation guide, a 3″ head lap is specified for concrete tiles. How much variation is allowable? Would a 2 1/2″ head lap be acceptable?
A. It is required that the roofer prepare the layout of the roof for a minimum three-inch headlap of the field tiles. Minor variations due to variances in tile lengths or roof inconsistencies are fairly common and will typically not affect the function of the roof. If however, the entire roof has been installed with less than the required headlap, it could make the assembly more susceptible to wind-driven rain in severe storm situations. This is less of a hazard on steep slope roofs and may never actually result in roof problems at all. If you are having problems related to this issue, I would discuss it with your contractor to see what could be done to correct the problem.
Q. I purchased and installed a tile roof, and it looks great. The installation guidelines do not specify an exact overhang at the eaves for the tile. Is there a minimum overhang (1/2 in?) code requirement? If so, what is it?
A. The codes do not define a minimum overhang although 1/2″ has always been sort of an industry standard. The reason the code doesn’t address this is that there are so many different circumstances that may affect what is required in any given area. In areas subject to heavy snow accumulation, for instance, overhangs are sometimes eliminated altogether and replaced with metal flashing. As long as the water is effectively directed off of the roof, the length of the overhang is left to the owner and contractor.
Q. We got 2 quotes from roofers on reroofing our house with concrete tiles. The roof pitch is 20 degrees. One installer says we need battens and the other one says we do not need them. Who is correct?
A. At a 20 degree roof slope (~4:12) battens are optional. At this roof slope, the tiles may be fastened directly to the roof deck as long as each tile is, in fact, fastened to the deck. If battens are incorporated into the installation and the roof is not located in a designated high wind area, standard weight tiles may be hung on the battens without fastening except for the perimeter areas as defined by the building code. Lightweight tiles must be fastened in all situations regardless of wind zones or batten status.
Q. Since the tile is usually nailed to battens I assume the tile is designed to provide a watertight seal. The felt membrane provides a cushion and protects against condensation and occasional water intrusion. If this is true, then if you have a leak the cause is either broken tiles or improper vents/exhausts or perhaps porous mud around ridges. Is this correct?
A. All steep slope (>2.5:12) roofing materials, including concrete roof tiles, are considered as water-shedding assemblies and are not water-tight. The purpose of the underlayment, in most cases, is to serve as a back-up system in the event that water gets underneath the tile. The amount of water that gets under the tile is minimal in all but the most severe weather conditions unless you have a System 1 Florida application which relies more on the sealed underlayment for protection. If a roof leak occurs, it is usually due to a breach somewhere in the underlayment or flashing system.
Q. I was considering the use of Polypro adhesive between the lightweight tile & underlayment to improve walk-ability. After reading the ICBO report ER-5595 which requires a single layer of 90# underlayment, my conclusion is to stay with 2 layers of 30# material and forgo the foam product. I interpret the need for 90# underlayment is due to the stress that earthquake, wind and/or walking creates on the underlayment bonded to the tiles which will allow leaks if it fails. I believe 2 layers of #30 underlayment without adhesive allows tiles to move over the underlayment during earthquake, etc, with much less chance of underlayment rupture. I want to opt for no leaks, & will tolerate possible broken tiles. Use of properly padded boards during painting or other maintenance should prevent tile breakage.
A. The use of polyurethane foam beneath tiles for improved walk-ability on service areas is a viable option but it does not require the use of 90# unless the foam is being used as a method of attachment. Regarding your concerns about rupture or tearing due to earthquakes, I know of no studies that show any advantage of one underlayment system over another and based on the most recent Whittier Narrows and Northridge earthquakes, this was not a problem that was widely reported.
Q. I have two turret roofs, 12/12 slope and radiuses of 6’6″ and 9’0″. Can I use your product to cover these turrets?
A. Interlocking tiles do not lend themselves well to application onto a radius surface since one of the features of most tiles is a longitudinal interlock that is invariably removed from the tile as cuts are made to follow the radius. That being said, I have seen some remarkable examples of this application that are the result of painstaking planning and hard work. In essence, the tiles must be cut in ever-decreasing sized pie-shaped pieces as the coursing moves upward towards the apex of the turret. Since the interlocking feature that provides the tile’s water shedding capability is typically cut away, the tiles will become essentially decorative and will require a fully sealed underlayment beneath the tile. In many cases, new nail holes will also have to be drilled for the attachment of the tiles. All in all, this application requires a lot of additional work.
Q. What is your position on the use of radiant barrier under concrete tile roofs with 90# membrane that is hot mopped lapping joints? Will this adversely affect the life of the membrane?
A. Radiant barriers come in several forms, i.e. rolled material, paints, laminates, etc. They are generally effective at reducing attic temperatures in the summer. I know of no studies that imply a direct impact on the underlayment itself. Generally, if the roof installation, methods, and workmanship keep the system as dry as possible–and if the system allows air flow–this dynamic will extend the life of all the components.
Q. When we install rake tiles, what are the recommended types of nails that we should use? Each rake tile requires two nails. The concern here is that these nails are exposed to the weather given they are visible along the sides of the homes.
A. The UBC building code requires only that the fasteners be corrosion resistant and penetrate the framing a minimum of 3/4-inch. The degree of corrosion resistance required will typically depend on the climate and environment. The minimum corrosion resistance noted in the latest TRI Installation Guide calls for nails complying with ASTM A641 Class 1. In coastal areas or other areas known to be highly corrosive, stainless steel or other non-ferrous materials may be considered.
Q. The contractor wants to nail only the first row of the tiles. Please let me know if this is the right way.
A. If the tiles are installed on battens and the roof slope is less than 5:12, the only tiles that need to be nailed are at the roof perimeters. The perimeters are defined as the first three tiles from the eaves, rakes, hips and ridges. If the roof slope is between 5:12 and 12:12, alternate courses of tile must be fastened in addition to the perimeter tiles. Above 12:12 slope, all tiles must be fastened. In areas designated by the building official as high wind regions, all tiles must be fastened at all slopes. Lightweight tiles (< 8 psf) must be nailed individually at all slopes, in all regions. If battens are not employed, all tiles must be fastened at all slopes. Specific guidelines are contained in the Uniform Building Code (UBC) in Table 15-D-2.
Q. One local contractor has told us that it is not necessary, in his opinion, to nail down EVERY tile. His usual practice is to only nail the tiles around the perimeter. How important is it that every tile be nailed down?
A. There are a number of different fastening requirements for concrete tile depending on the type of application, the roof slope and the local building requirements. The Uniform Building Code Table 15-D-2 stipulates that tiles installed on battens need only to be fastened at the perimeter of the roof (three tiles in from eaves, rakes, ridges and hips)at slopes less than 5:12. From slopes of 5:12 to 12:12, alternate courses must be fastened in addition to the perimeter. Above 12:12 all tiles must be fastened. In areas designated as snow areas by the local building official, all tiles must be attached with two fasteners or with one fastener if installed on battens. Your contractor may very well have had good success without fastening all tiles, but these are the code requirements and are not left to your roofer’s opinion.
Q. I have an open beam ceiling with 2×6 tongue and groove. I have a 1 inch sheet of insulation with shakes over that. I want to add 2 more inches of insulation over the existing. What has to be done to put a concrete tile roof on?
A. Since you have an existing shake roof, I would assume that the shakes are attached to 1″x6″ spaced sheathing that is installed above the 1″ insulation. You did not mention whether you intended to remove the 1″x6″ or add the new insulation on top of it. Whichever assembly you select, you should be cognizant of the need to attach the new roof deck and/or roofing material to the support system of the roof. In your case this would be either the 2″x6″ roof sheathing or the rafter system. The tiles may be attached directly to a solid roof deck or to a batten system. As long as you make certain that the roof deck and/or batten is securely attached to the roof structure, you may proceed as normal with your installation. I would also like to point out the importance of proper ventilation on this type of application. The UBC building code requires ventilation of roof structures and this includes open beam and cathedral ceilings. There should be some space in your assembly for venting.
Q. Can Hip and ridge sealer be used as a glue to hold small cut tiles in place? If so is it a good strong glue that won’t weaken in the heat of summer? I want to hold tiles at the valleys of my new roof because I hear that you aren’t supposed to nail at all at the valleys.
A. Unless the manufacturer specifically states that his material is designed for the attachment of concrete roof tiles, I would not use it as such. There are other adhesives available that are specifically designed for the attachment of cut tile pieces and they may be used to attach individual tiles to adjacent tiles that are mechanically attached. When using these adhesives on steep slopes or in valleys, it may be necessary to further attach the tile with wires to keep them from sliding prior to the adhesive bond.
Q. I need to find out what the maximum slope is for tile installation on a roof.
A. Tiles may be installed on any roof slope but, on slopes exceeding 24:12(200%), the nose ends of all tiles must be securely fastened. This is typically accomplished with special clips and/or adhesives.
Q. When installing the roof ridge tile, what is the minimum overlap between ridge tiles?
A. Ridge tiles must be lapped sufficiently to cover the nail holding the preceding tile. This nail hole must be sealed with roofing cement or other adhesive that will effectively seal the nail hole and provide a firm bond between the two tiles.
Q. We are planning to install colonial slate tile on a dome roof with varying pitch from approx. 12:12 to 2:12. What kind of special precautions should be used to prevent wind driven rain from penetrating the system of the lower slopes?
A. It is difficult to totally prevent the entry of wind driven rain into low slope roofs but there are steps that may be taken to guard against leakage and roof damage. Increasing the head lap of the tiles installed at low roof slopes can be helpful in preventing water intrusion but steps must still be taken to prevent damage beneath the tiles. On slopes below 3:12, a sealed underlayment is required and a counterbatten system is required to keep the battens and tile above the roof deck to prevent damming and minimize fastener penetrations.