Abstract: A method for applying a roofing membrane may include unrolling an adhesive material onto a roofing board to adhere a bottom surface of the adhesive material to the roofing board. The method may include removing a release liner from the adhesive material to expose a top surface of the adhesive material. The method may include applying a roofing membrane to the exposed top surface of the adhesive material to adhere the roofing membrane to the roofing board.

Abstract: A mounting device includes a first arm, a second arm positioned parallel to the first arm, and a top plate coupled to the first arm and the second arm. The top plate includes a center portion, a first coupling panel formed at a 90 degree angle with respect to a surface of the center portion, and a second coupling panel formed at a 90 degree angle with respect to a surface of the center portion. The second coupling panel is located at a side of the center portion opposite the first coupling panel.

Abstract: Apparatus for shielding a structure from bullets is disclosed. The structure includes an outside wall which has a vertical stud. The apparatus includes a prefabricated panel which has an armor plate having a front side and an opposite rear side. An exterior finish substructure is connected to the front side. After fabrication, the prefabricated panel is transported to the structure and connected to the vertical stud of the outside wall of the structure.

Abstract: In various representative aspects, an assembly for securing a solar panel rail and rail-less support structures to a shingle roof. More specifically, the apparatus includes a connection bracket and flashing device for use in installing solar panel rail support structures. The connection bracket is secured to the flashing device by rotating its base around a threaded connection until it locks in place so that a solar panel rail support guide can be connected to a generally U-shaped connection on the top of the bracket. The apparatus also offers an improved means to cover the penetration point on the flashing to protect it and prevent water from leaking into the roof as well as an improved way to install the apparatus over existing products. An alternate embodiment of the apparatus is offered to support a rail-less pivot mount as well.

Abstract: A fastener cap system can include a rigid cap and a sealing member which forms a liquid barrier so moisture is impaired from entering a space under the rigid cap and/or around a fastener installed through it. The sealing member can include a central seal disposed on an upper surface of the cap, the seal extending beyond a head of a fastener, which extends through the cap and sealing member, so that moisture is impaired from entering the cap under the head. The sealing member can be above and below respective lowermost and uppermost cap surfaces so the cap system can be fed cleanly and efficiently through a cap feeder during installation via a tool. The sealing member, which can have a higher coefficient of friction than the rigid cap, thereby does not drag along a cap feeder and cause feeding issues. Related methods of manufacture and use are provided.

Abstract: Disclosed herein is a roof mount installation assembly. The roof mount installation assembly includes a roof mount, a flashing patch, and an adapter cap. The roof mount has a base and a threaded post. The flashing patch has an opening. The flashing patch is configured to surround the base. The opening is configured to allow the threaded post to extend therethrough. The adapter cap is configured to be removably mounted over the flashing patch. The adapter cap is configured to apply a force to the flashing patch for sealing the flashing patch around the roof mount.

Abstract: A concrete slab underlayment product is used at an excavation area at which a concrete foundation slab is to be poured. The underlayment combines a vapour barrier layer with a set of foam insulation bodies. The vapour barrier layer spans fully over the entire set of foam insulation bodies, which are spaced apart from one another at least at lower ends thereof opposite the vapour barrier layer. This leaves drainage/air spaces open between the foam insulation bodies when laid in an installed position atop the floor of an excavated area. In use under a concrete slab, the vapour barrier layer forms a gas and moisture barrier, and the foam insulation bodies and the drainage/air spaces therebetween form a combination of void spaces, drainage channels and insulation blocks between the concrete slab and the floor of the excavation area.

Abstract: A fastener plate for use in coupling an underlayment to a roof surface is disclosed. In use, the fastener plate is arranged and configured to enable subsequently applied liquid coatings to flow through a top surface of the fastener plate and into one or more cavities so that the liquid coating seals any openings created by introduction of the fastener. In one embodiment, the fastener plate may include a top surface, a bottom surface, a fastener opening for receiving a fastener, a plurality of openings formed in the top surface, and one or more cavities positioned between the top surface and the bottom surface, the one or more cavities being in fluid communication with the plurality of openings so that the liquid coating can flow through the plurality of openings formed in the top surface and into the one or more cavities to seal any voids created by the fastener.

Abstract: A fixing disc (1) for initially fixing a fastening element (2) in an opening of a component to be fastened, in particular a facade panel, during mounting of the fastening element (2) and for cutting into and/or removing a defined region of a protective film on the component to be fastened during mounting of the fastening element (2) is described. The fixing disc (1) has a fixing means for initially holding the fastening element (2) in a predetermined position relative to the opening during mounting of the fastening element (2), at least one connecting means (4) for at least temporarily producing a connection between the fixing disc (1) and the fastening element (2), and at least one cutting and/or friction means (5) on that side of the fixing disc (1) which faces the component to be fastened.

Abstract: A mounting system for attaching an object to a roof structure includes a roof membrane placed on to the roof structure, a mounting plate, an elastic membrane secured to the roof membrane. The mounting plate includes a fastener, the fastener being secured to the mounting plate and extending therefrom, the fastener is configured to secure the mounting plate to the roof structure, which in turn secures the roof membrane to the roof structure, the fastener is configured to extend through a thickness of the roof membrane; and a protrusion extending from a top surface of the mounting plate, the protrusion is configured to secure the object to the mounting plate.

Abstract: An underlayment system for a roof structure including underlayment material disposed in covering relation to a roof deck and a plurality of mechanical fasteners disposed and structured to interconnect the underlayment material to the roof deck. Each mechanical fastener includes an outer plate, an under plate and a connector penetrating through both the outer plate and under plate in secured relation to the roof structure. The under plate is disposed and structured to sealing engage the connector penetrating there through. The under plate is further disposed in engagement with an undersurface of said outer plate and beneath and in segregating relation between an outer peripheral edge of the outer plate and the underlayment material.

Abstract: Fastening system (1) for fastening an attachment (18) to a substrate (13) with an insulation layer (16), the fastening system (1) comprising an anchor bolt (2), with a first area (3) for anchoring in the substrate (13), a second area (4) to which the attachment (18) can be fastened, and a stop (5), a mounting tool (6) to form an opening in the insulation layer (16), and a sealing element (7) adapted to be disposed at the stop (5) after the mounting tool (6) has been removed and to seal the opening in the insulation layer (16) as well as a corresponding method.

Abstract: A tie system is provided for use with a wall form for a cementitious backup wall and for use with a wall tie to connect between the cementitious backup wall and a veneer. The tie system includes a backup wall connector and a form connector. The form connector is connectable to the form and secures the backup wall connector in position as the wall form is filled. The connector may have heat transfer reducing perforations. The connector may have an outwardly positioned flange to which external wall members may be attached. The connector may have multiple gap-setting features.

Abstract: A passive vent for venting a building enclosure having an opening in a roof portion, the vent being adjustable for mounting on roof portions of different slopes. The vent has a base pivotally attached to a vent structure with a pair of pivot joints. The vent structure has a collar attached to a vent body having a cover. At least one gas permeable screen is positioned on the vent body between the cover and the collar. The base comprises a lower attachment structure for attaching the base to the roof portion over the opening. An aperture through the lower attachment structure permits gas to pass in to and out of the opening in the roof portion through the base. A wall including a pair of opposed curvilinear wall sections surrounds the aperture. The pivot joints define a pivot axis about which the vent structure pivots along a range of angles relative to the base.

Abstract: A flashing laminate includes a non-reinforced thermoplastic sheet having a bottom surface, a first longitudinal edge, and a second longitudinal edge. The flashing laminate also includes an adhesive layer on a longitudinally extending portion of the bottom surface adjacent to one of the longitudinal edges. In one or more embodiments, the laminate also includes a release liner positioned over the adhesive tape.

Abstract: A system for assembling two-sided walls on, through, and around a pre-installed structural steel grid. System wall units have an outer side and an inner side, the outer side being an outer wall surface, the inner side opposing an inner side of one or more wall units on an opposing side of the structural steel grid. Interlock elements extend through spaces in the structural steel grid and connect opposing wall units to prevent separation of the opposing wall units. Installed in courses, the wall units create a continuous void between opposing wall units, such that structural void fill material can be poured into the assembled wall at one or more openings, and the void fill material will fill the continuous void from the top of the wall to the bottom of the wall. Plumbing, electrical, and other building systems can be installed on the steel grid prior to wall assembly.

Abstract: A load transfer device is provided to connect concrete elements including, but not limited to, sandwich and double wall panel wythes, roof, floor, balcony and canopy members, and pavement. The device may be used to connect and transfer loads between the components of sandwich and double wall panels. The device includes two load transfer members positioned at an angle with respect to one another. Additionally provided are a retention housing for retaining one or more load transfer members at their angled positions and a depth locating means for retaining one or more load transfer members at their proper depth. Also provided are sandwich wall panels and double wall panels employing the load transfer device and methods for manufacturing sandwich wall panels and double wall panels employing the disclosed load transfer device.

Abstract: A prefabricated rain screen wall panel is provided comprising inner and outer concrete panels secured together by shear connectors. Intermediate members provide insulation, a drainage channel and a vapor barrier.

Abstract: A pre-engineered metal building configured to reduce air leakage through the shell of the building by providing an insulation system for fully sealing an enclosed space within the structural frame of the building. The insulation system includes a vapor barrier that defines the enclosed space, at least one insulation layer, and a continuous air barrier. Roof sheeting and side wall facing are attachable to the structural frame to form a shell about the building, and at least a portion of the insulation system is positioned between the shell and the structural frame.

Abstract: A water impermeable structure comprising a plurality of construction boards fastened to a structure or a building. Each construction board comprises a curable substrate and a water impermeable seamless resilient membrane adhered to the curable substrate. The water impermeable seamless resilient membrane comprises one or more flaps that extend beyond the curable substrate. The flaps affix to the adjoining construction board creating a water impermeable structure and a water impermeable structure with at least one water impermeable area.

Abstract: A system for assembling a pre-engineered building with a monolithic vapor retarder to control the formation of condensation on the walls. The system allows for numerous different combinations of insulation thickness, different kinds of walls, inside vapor retarders in different rigid panels, different facings or membranes. The system further provides for finished inside surfaces with high thermal quality.

Abstract: A mounting system for solar modules in which a mounting beam has its opposite ends bent downwardly to form a first and second leg that hold photovoltaic modules at an angle to a flat roof, wherein the first and second legs are screw fastened into a rafter and the bottom ends of the first and second legs are placed into receptacles into which sealant is poured, thereby forming a water-tight seal preventing any water from leaking into the holes formed by the fasteners securing the first and second legs to the building rafters.

Abstract: An apparatus and method for attaching a protective barrier to a surface, such as a wall, ceiling or floor. The protective barrier can be plastic sheeting or any other suitable, material, which is impermeable by water, dust, debris and related contaminants. The apparatus and method for its installation and use being capable of connecting the protective barrier to a surface so that no dust, debris or other contaminants can pass between the protective barrier and the surface to which it is being attached.

Abstract: A roof attachment assembly for mounting to a roof substrate. The roof attachment assembly comprises a plate having a substantially frustoconical protrusion defining an aperture extending therethrough, the plate defining a first surface and a second surface, the first surface facing the roof substrate and the second surface spaced from the roof substrate. The roof attachment assembly also comprises a membrane positioned adjacent one of the first surface and the second surface of the plate, and a bracket positioned proximate the second surface of the plate, the bracket operable to support one or more roof mounted fixtures. The roof attachment assembly further comprises a fastener extending through the bracket, the membrane and the plate, the fastener operable to couple the bracket, the membrane and the plate together, wherein the roof substrate is contiguous adjacent to an end of the fastener.

Abstract: A roof mounting system for mounting one or more roof-mounted fixtures to a roof includes a roofing system having a top surface and a roof attachment assembly mounted to the top surface of the roofing system. The roof attachment system includes a plate having an aperture, at least one membrane patch coupled to the plate, at least one disc including a disc aperture, a nut, and a first fastener including a head positioned adjacent the at least one membrane patch and a shaft extending through the at least one disc aperture and the nut. A second fastener includes a head positioned adjacent the plate and a shaft extending through the plate aperture and through the roofing system top surface, to connect the roof attachment assembly to the roofing system.

Abstract: A roof insulation fastening system employs a fastener and a compression plate with a tube which interacts with the compression plate to permit the plate to vertically move relative to the head of the fastener when the adjacent area and/or plate is subject to excessive compression. The tube includes a retainer shoulder and a pair of tabs wherein the plate captures the tube. The tube includes a throat and a tapered portion with a throughbore. The fastener is inserted into the tube and secured in place so that the head is retained at the intersection of the throat and the tapered portion and the shank is secured into the roofing substrate.

Abstract: A roofing support system includes a spacer bracket having a lower edge adapted to pierce through a layer of insulation to abut in direct contact with a purlin, a fastener that fastens the spacer bracket to the purlin, and an upper portion adapted to support a beam above the insulation layer and in spaced relationship to the purlin.

Abstract: A system and method for insulating a metal roof include a blanket of insulation laid over at least one purlin. A series of thermal blocks are fastened above the purlin over the blanket of insulation. Each thermal block in the series of thermal blocks has legs that pin the blanket of insulation to a top of each purlin. Gaps are defined between the legs, the gaps enabling regions between the legs wherein the blanket of insulation is only partially compressed between the purlin and an underside of each thermal block. Each thermal block can include a first end, a second end, and a first leg between the first and second ends. The first end includes slots for receiving clip legs of a first roof clip. The second end includes an abutment surface and a landing surface for receiving a next thermal block in a series of thermal blocks.

Abstract: Apparatus and methods for installing a penetration in a sheathing assembly and building structures. An opening can be formed at least partially through a sheathing assembly that includes a body; a barrier layer; and an adhesive disposed between at least a portion of the body and the barrier layer. At least a portion of the barrier layer adjacent the opening can be peeled back to expose at least a portion of the body. A penetration can be disposed at least partially within the opening. The penetration can include a contact member that at least partially contacts the exposed body, the barrier layer, or both. The penetration can be secured to at least a portion of the sheathing assembly, and the peeled back portion of the barrier layer can be repositioned such that the barrier layer covers at least a portion of the contact member.

Abstract: A roofing system includes a plurality of insulation boards adapted for overlying a roof deck to form a layer of insulation, and a plurality of cover boards adapted for overlying the layer of insulation. Each insulation board includes a foam material that includes polyisucyanurate, the foam material having a first density. Each cover board includes a material including polyisocyanurate, the material having a second density greater than the first. The roofing system may further include a waterproofing membrane adapted for overlying the cover boards. The insulation boards and cover boards may include facers on top or bottom surfaces.

Abstract: The system and method of securing a single ply membrane to a roof deck or structure described utilizes sections of cable or reinforced membrane material that are completely protected or surrounded by the single ply membrane. A set of perimeter cables or interior cables secure the membrane to a roof decking by stretching the cables or reinforced membrane sections until taut. The cables are secured at their endpoints and additional fasteners may be provided along their lengths. Membrane material is used to weatherproof the fastening of the cables to the roof decking.

Abstract: A roofing system includes an insulation layer and an exposed fiber surface of a sheet. A cement layer is placed intermediate therebetween. An elastomeric outer weatherproof coating overlies the sheet. A process for applying to a roofing system is provided that includes applying to a roofing substrate an insulation layer having an upper surface. Wet cement is applied on the upper surface of the insulation layer. An exposed fiber surface of a sheet is placed in contact cement. The sheet is then either directly or with intermediate layers therebetween overlayered with an elastomeric weatherproof coating. An insulation board is also provided that includes an exposed fiber backing. The exposed fiber backing accepts an overlayer of elastomer, cement, or mastic.

Abstract: A vapor retarder system includes a vapor retarder sheet. At least one and typically a plurality of parallel spaced-apart tie-straps are located adjacent an inner surface of the sheet, and the tie-strap extend across a width of the sheet and are connected to the sheet at multiple connection locations that are spaced from each other along a length of the tie strap. The sheet includes drape regions where the sheet is disconnected from the tie straps between successive connection locations. The tie-straps and drape regions ensure that the vapor retarder sheet is installed over roof purlins with the proper drape between the purlins to obtain the required insulation R-values. A fall-protection net or sheet can also be constructed and/or installed in the same manner.

Abstract: A roofing system includes a plurality of insulation boards adapted for overlying a roof deck to form a layer of insulation, and a plurality of cover boards adapted for overlying the layer of insulation. Each insulation board includes a polymer foam material having a first density. Each cover board includes a material including polyisocyanurate, the material having a second density greater than the first. The foam material of the insulation boards may include, for example, polystyrene, polyurethane, or a phenolic material. The insulation boards and cover boards may include facers on top or bottom surfaces.

Abstract: A cover board composite for overlying insulation of a roofing system includes a high-density core layer that is at least predominantly of a polymer material, a facer overlying and bonded to a bottom major surface of the core layer, and a reinforcement interposed between the facer and the bottom major surface of the core layer to coincide with a fastener pattern for securing the cover board composite to a roof deck and increase a per-fastener wind-uplift pull through rating for the cover board composite.

Abstract: The system and method of securing a single ply membrane to a roof deck or structure described herein is of a system that utilizes sections of cable that are completely protected or surrounded by the single ply membrane. There may be a set of perimeter cables or interior cables that secure the membrane according to the needs of the building and the necessary specifications on the roof. The cables are secured at their endpoints and, possibly, additional fasteners may be provided along their lengths. Flashing of the cables provides that they be completely protected from the elements, as are most fasteners in flat or low slope roofing systems.

Abstract: A method and apparatus comprising providing a temporary or permanent connection of one or multiple sheets of material and providing an attachment point to hold these materials. A mating two part base and cap connected by a central tube connector that securely sandwiches sheet material between the two. The base may have additional passthrough holes for affixation to supports or ground. The connector may be threaded or frictionally attached and may optionally have thumb wings for easy turning. The connector may have one or more wings for easy manipulation. The connector may also be configured to receive various staking means including ones with eyelits or other attachment points and have pass throughs for stable engagement to other structures.

Abstract: A foam roofing underlayment is provided with a reinforcement membrane having an array of fastener elements for engaging fastener elements on a flexible roof membrane. The underlayment is formed by molding foam between the reinforcement membrane and a carrier membrane. The underlayment in secured to the roof using washers having fastener elements for engaging the fastener elements of the flexible roof membrane. An anti-peel flap with fastener elements is provided around the periphery of the washers. A slip sheet is used between the underlayment and the flexible roof membrane to permit accurate positioning of the flexible roof membrane prior to engagement of the fastener elements. The interstices between the fastener elements provide lateral moisture paths to vents in the flexible roof membrane.

Abstract: A foam roofing underlayment is provided with a reinforcement membrane having an array of fastener elements for engaging fastener elements on a flexible roof membrane. The underlayment is formed by molding foam between the reinforcement membrane and a carrier membrane. The underlayment in secured to the roof using washers having fastener elements for engaging the fastener elements of the flexible roof membrane. An anti-peel flap with fastener elements is provided around the periphery of the washers. A slip sheet is used between the underlayment and the flexible roof membrane to permit accurate positioning of the flexible roof membrane prior to engagement of the fastener elements. The interstices between the fastener elements provide lateral moisture paths to vents in the flexible roof membrane.

Abstract: Provided is a roofing system comprising a thermoplastic roofing membrane and one or more raised metal profiles attached to the thermoplastic roofing membrane. In an embodiment, provided is a method of improving a roofing system comprising a thermoplastic roofing membrane. The method comprises installing one or more thermoplastic coated raised metal profiles on the roofing system. A side of the one or more thermoplastic coated raised metal profiles comprises a thermoplastic layer. Installing the one or more thermoplastic coated raised metal profiles on the roofing system comprises welding the thermoplastic layer to the thermoplastic roofing membrane. The presently disclosed raised profiles provide not only desirable aesthetics to thermoplastic roofing systems, but can also provide structural benefits to the roofing system.

Abstract: Anchoring systems for use in cavity wall structures having an inner wythe constructed of interengaged composite panels and a veneer outer wythe are disclosed. The wall anchor is disposed within the juncture of the interengaged composite panels and fastened to the frame. The wall anchor maintains a strong interlock with the composite panels and backup wall, maintains insulation integrity and limits thermal transfer, without obstructing the juncture of the composite panels. The anchoring system interlocks with varied veneer ties, allowing vertical and horizontal adjustment for alignment with the bed joints. The anchoring system for composite panels provides an economical, high strength, low weight, insulated backup wall construction for interengagement with a veneer outer wythe.

Abstract: A roofing system includes a plurality of insulation boards adapted for overlying a roof deck to form a layer of insulation, and a plurality of cover boards adapted for overlying the layer of insulation. Each insulation board includes a foam material that includes polyisocyanurate or polyurethane, the foam material having a first density. Each cover board includes a material including polyisocyanurate or polyurethane, the material having a second density greater than the first. The roofing system may further include a waterproofing membrane adapted for overlying the cover boards. The insulation boards and cover boards may include facers on top or bottom surfaces.

Abstract: The invention relates to an attachment element for studded plastic sheets comprising a base body with at least one stud projecting from a front of the base body. To provide an attachment means that results both in a tear-resistant attachment of the studded plastic sheet to the building wall and in extensive surface contact at a top edge of the studded plastic sheet, it is provided that a head portion is arranged on the base body, which fully or at least partially projects from the front of the base body with a resiliently deformable area.

Abstract: Systems and methods for a secure metal roofing system are provided. The secure metal roofing system includes one or more elongate bars. The elongate bars include a number of slots spaced apart from one another in a longitudinal direction. Fasteners are disposed within the respective slots for securing the elongate bars to the roof structure. In this manner, the slots are sized and shaped to accommodate a difference in thermal expansion between the elongate bars, the fasteners, and the roof structure so as to minimize or prevent the fasteners from backing out of the roof structure due to changes in thermal and/or environmental conditions. The secure metal roofing system includes one or more roofing panels and a number of fasteners configured to secure the roofing panels to the elongate bars. Further, a moisture barrier is disposed between the roof structure and the elongate bars and roofing panels.

Abstract: The invention relates to a dowel having cutting devices at the lower side of the pressing plate at the circumference of said pressing plate for cutting into the insulating panel when the pressing plate is pulled into the insulating panel. The invention further relates to a method, in which a bore-hole is drilled through the insulating panel into the substructure, the dowel and the expansion element are inserted into the bore-hole, the expansion element is driven into the pressing plate and the dowel sleeve, and wherein simultaneously the pressing plate is pulled into the insulating panel under compression of the insulating panel, and the insulating panel is cut in at the circumference of the pressing plate by means of cutting devices.

Abstract: The invention relates to an under rafters insulation system for a steep roof, comprising at least two mutually parallel extending building elements (3) which are spaced from each other, and insulation elements (4), in particular mineral fiber insulation elements, are arranged in a space between the building elements (3). The building elements (3) are mountable to rafters (2) of the steep roof by means of holding elements (5). For further developing an under rafters insulation system of the described type to the effect that the insulation elements (4) are easily supported between the building elements (3) at least over a period of time in which the under rafters insulation system (1) is not yet completed with a final cover, it is proposed that the holding elements (5) additionally secure the insulation elements (4) against falling out of the space between the building elements (3).

Abstract: A roof membrane is disclosed, for use in simulating a standing seam metal roof when applied to a roof surface and a roof system is also provided, that employs the roof membrane, disposed between longitudinal, but spaced-apart, generally parallel roof battens. Underlayments of various constructions are also provided, beneath the membrane, as an option. Caps are provided for upstanding legs of the roof battens.

Abstract: A system and method for insulating a metal roof includes a thermal block arrangement disposed over each of a pair of purlins. A vapor-barrier sheet spans between and is secured over the opposing pair of purlins, the vapor-barrier sheet being secured underneath each thermal block arrangement. A batt insulation receiving cavity is defined by an upper surface of the vapor-barrier sheet and between opposing faces of each of the thermal block arrangements.

Abstract: Each of a plurality of vertically disposed trusses having angled rafters and a joint is coupled to a ridge board. Upper TboxTrusses function as the rafters. Each upper TboxTruss has a planar plate. The planar plate has a hollow box depending downwardly there from. An interior sheet of fire resistant fabric sheet material is above the upper TboxTrusses. An exterior sheet of the fire resistant fabric sheet material is below the upper TboxTrusses. Insulation material is located between the interior and exterior sheets and bounded by adjacent hollow boxes.

Abstract: A roofing membrane retainer is provided having a cylindrical plate. The cylindrical plate has a central aperture for receiving a fastener. The plate also includes a pair of concentric inner and outer raised reinforcing ribs and a plurality of scoop-shaped projections. The scoop-shaped projections extend downwardly from the plate in concentric inner and outer cylindrical arrays. The inner cylindrical array of projections and the outer cylindrical array of projections are radially outward of the inner rib and the outer rib, respectively. The projections each comprise a scoop with a base periphery having an open mouth edge and a remaining peripheral portion contiguous with the plate. The projections in each array are spaced equidistance about the plate. The mouth edge of adjacent projections are oriented in alternating radial inward and outward directions.