Flat roofs are the simplest of roofs and easily accommodated with the Utilihab system by duplicating the same Secondary floor frame structure at the top of the Primary frame. For a roof overhang, the same structure employed for the perimeter decking is used. Where the roof is not used as a walkable deck, spacer frame members are omitted and the overhanging frame can be left cantilevered up to a meter wide. Self-supporting roofing panel systems, such as the Epic roof systems or alloy SIPs, are preferred for Utilihab and can eliminate most or all Secondary framing pieces, the panels relying on attachment to just the Primary framing and its overhang extensions alone. Traditional composite roofing for flat roofs is not recommended for use with Utilihab as it is not demountable and does not employ modular components.
In the simplest approach, roofing panels are aligned perpendicular to the roof joists and attached either by simple through-panel bolts to T-nuts in the upper profile slots of the joists and parallel Primary roof beams. Standard weather-strips or wear strips can be used in the upper slots as well to cushion the paneling and reduce sound transmission. Weather strips or foam tape is employed along the Primary frame perimeter as a seal and some panel products may include special shaped profile strips to accommodate sealing along panel corrugations. In some cases wood or plastic battens may be employed between joists and roof panels to create a slight curve that assists drainage. The standard 1m spacing of the Utilihab Secondary framing grid is generally sufficient to support most corrugated or SIP panel products.
For very flexible materials without integral insulation aluminum alloy channel purlins (‘z’ or ‘c’ shape) may be used to provide additional rigidity for the roof panels, the panels bolted to these rather than the roof joists.
A roof underlayment of plywood or cement panel may also be used to support a sandwich of rigid foam insulation panels on top of which the thinner alloy roof panel are laid and through-bolted. These panels are simply clamped in place between joist and roof panel without additional attachment. In some cases, rigid foam paneling may be used alone when it has a sufficiently resilient surface -usually an aluminized backing.
In the case of SIP alloy roofing with their own integral insulation, no underlayment is necessary and the panels may be attached from the underside of the roof using screws running in prepared holes though the joists or on small angles attached to the profile sides. A special angle-clip profile may also be employed which locks between one flange of a side profile slot and is clamped in place as the screw attaching the roof panel is tightened.
Some roofing panel systems employ special locking strips or base roof deck that are attached by through-bolts to the joists first and then the roofing layer is snapped or bolted in place to that, fully concealing the roof attachment and eliminating much assembly labor. In the case of structural decking, these lower planks can provide a fully finished appearance, eliminating the need for the standard ceiling grid, and sometimes support special channel hangers that lock into plank slots to allow hanging of lights, utilities, or suspended ceiling grids. They can also sometimes form the basis of walkable roof decks.
Membrane roofing is supported using single-piece prefabricated membrane sheets matched to specific roof dimensions. Preferred materials are elastomeric and EPDM, which offer ease of handling and safety from chemical leaching so that run-off can be collected and re-used in rain catchment systems. With Utilihab’s standard unit dimensions, made-to-order roof membranes are easily fashioned for a variety of roof forms. Normally, the Utilihab system favors more modular roofing, but for use with green roofs and walkable decks a continuous membrane roofing may be the only practical option. The compromise is that re-use of the membrane is precluded and expansion without whole membrane replacement requires adhesive joining of the old and new membrane sections.
Membrane roofing installation is performed by first preparing a foundation surface using fiber-cement panel, plywood, or specialized rigid insulated foundation panel. Panels are mounted in alternating pattern with counter-sunk button heads bolts to T-nuts on the upper profile slots and with ends over joists lap-joined. Additional layers of foundation panels, with rounded edges may be attached on top of the base panel layer to provide a slight curve to the roof surface to help shed water. Plastic end-cap covers are applied to the vertical post corners of the structure and plastic wear strips or wood cover plates with countersunk screws applied to the exposed top edge T-slots. Adhesive is then applied to the cleaned deck surface and the pre-made membrane is rolled on and smoothed. The edge overlap of the membrane is then glued to a plastic cover strip installed in the upper outside facing perimeter edge slots with enough overlap left free to cover the edge of gutters and fascia channels bolted along the lower adjacent slot. Corners are folded and glued flat. Penetrations of the roof membrane for plumbing, vents, skylights, and the like are accommodated by cut openings sealed with membrane flashing adhesive-bonded to the main membrane and surface of the penetrating shape and then sealed along flashing edges with a sealant. Some membrane materials makers offer ‘boot’ shape pre-formed flashing elements to accommodate common pipe and opening shapes.
Another possibly simpler mechanical attachment for membrane roof systems employs pre-fitting the prefabricated roof membrane with long snap-lock profile cover strips, usually along the shortest axis of the roof plane. The roof employs the standard floor grid and insulated fiber-cement foundation panels that are mounted just as sub-floor panels using press-fit battens. Optionally, they may be fixed into the battens by counter-sunk screws from the top. The foundation panels are mounted at a height to match the thickness of the profile cover strips, so they will lay flush. Additional cover strips are mounted on the spacers between the primary roof joists. The roof membrane is then mounted simply by rolling out and press-fitting the long snap-lock cover strips into the top profile slots. These are spaced so that the roof membrane is tensioned somewhat as each cover strip is plugged in. The two parallel side strips are then pulled over the edge of the roof and plugged into the upper perimeter facing profile slots. These may be additionally bolted in place to T-nuts using pre-made holes. Alternatively, a variation of a locking angle clamp profile may be employed. Formed as a flat plate adhesive bonded to the membrane, this is tensioned to fit a flange into the slot, engaging one side of the profile slot flange. This is then secured by bolts to T-nuts are pre-drilled points. An overlap of membrane material is left to cover the edge of gutter/facia channels attached to the lower perimeter facing profiles. The perpendicular sides are attached by adhesive using a double-sided tape to cover strips installed in those upper perimeter facing profile slots and, again, possibly secured by bolts and T-nuts in pre-made holes. This mechanical approach may be limited to smaller roof areas.
Flat roofs are finished with aluminum fascia channels along the perimeter edge of the roof line and perforated or screened soffit paneling along the underside of any overhang, all simply bolted to facing profile slots. Edge fascia will typically be ridged, offering concealment for raised seam roofing and may integrate a box gutter channel along the roof edge using perimeter edge spouts or gutter channels attaching to corner framing. (rain chains are another novel -though actually ancient- option for gutter drainage well suited to an Asian or Polynesian inspired look) Where a roof overhang is particularly large or the roof line is extended by features like pergolas, the hollow framing profile can be used as a drain channel. The profile framing can additionally allow for a unique Utilihab-specific fascia and soffit paneling system that uses 1m panels for the wide overhangs that snap-lock into the profile slots for simple assembly and a clean look. Recessed lighting is also commonly employed with large roof overhangs and is accommodated in the same fashion as its indoor forms. Additionally, strip lighting integrated into standard alloy cover strips can snap-lock along exposed profile slots.
[Study needed to identify specific compatible roofing panel products.]
[Study needed for angle-clamp profiles to see if off-the-shelf forms are available.]
[Study needed for adhesive-free mechanical attachment options for membrane roofing]