Corrugated Asphalt Roofing by Onduline North America
ONDURA® Quick Tips for Installation
Installing ONDURA Sheets On A New Structure:
On new buildings, ONDURA sheets install either over purlins or over solid decking covered by roofing felt. Over decking, simply follow these same instructions making sure that decking is secure before nailing down sheets. We strongly recommend solid decking for buildings with interior ceilings. If installing over purlins, space purlins 24” (60cm) for greater than 15° slope and space purlins 18” (45cm) for a slope between 10°-15°.
CAUTION: Avoid installation when the material temperature is below 32° (0°C).
Re-Roofing With Ondura Sheets:
ONDURA works well as a new roof over an old asphalt shingle roof. Over roofs with a uniform surface, just install sheets using nails long enough to penetrate 1" (2.54cm) into supports of the decking beneath. Over corrugated metal or other irregular roofs, first install nailer strips using lumber spaced appropriately for the slope of the roof, then lay ONDURA sheets per instructions. Be sure that nailing strips are securely in place.
Drive Nails Correctly:
Drive ONDURA nails only through the top of corrugations. Always drive nails perpendicular into purlins-not at an angle-so the rubber washer is snugly in contact with the sheet. See Fig. 1. Do not overdrive or underdrive nails. Slight hand pressure on a nailed-down corrugation should not separate the sheet from washer contact.
Pulling Nails From Sheets:
To pull a nail from sheet, use a claw hammer and a 1-1/2" (3,81cm) wood dowel or pipe. Put the dowel or pipe in the valley of the corrugation next to the crown with the nail to be pulled. Then use the dowel or pipe as a leverage point for pulling the nail. See Fig. 2.
Walking On ONDURA Sheets:
When walking on nailed-down ONDURA sheets, walk on top of purlins only placing feet across corrugations. Also wear soft-soled shoes. ONDURA is more pliable in hot weather and less pliable in cold weather. Always use care when walking on ONDURA or any other roof.
Installing The First Sheet:
- From the corner where the eave and rake meet, measure along the eave 48 inches (122cm) and mark.
- From the corner of the rake and the ridge, measure along the ridge 48 inches (122cm) and mark.
- Snap a chalk line connecting these marks for sheet alignment.
- Starting at the eave/rake corner, fasten the rake corrugation of the first sheet at each purlin along the rake (see Fig. 3 for Nailing Pattern).
- Now align the opposite edge of the sheet with the chalk line. Nail in place along the second corrugation from the chalk line to allow for the side lap of the next sheet. Be sure to install closure strip before nailing eave.
Finishing The First Row Of Sheets:
You can now install the remainder of the first row.
- From the first chalk line, mark off successive 44 inch (112 cm) spaces along the eave. Do the same at the ridge. (This 44 inch /122cm distance allows for a 1 corrugation side lap.)
- Snap chalk lines between the eave and ridge marks for sheet alignment.
- Noting the nailing pattern in Figure 3, install the rest of the eave row.
Installing The Second Row Of Sheets:
The second row can be installed so that all side-laps meet lower sheets in the middle, or so that all side-laps line up from row to row up the slope of the roof to offset the side lap of one row from the other.
To stagger the side laps from row to row, begin the second row with a sheet cut in half along its length (see Fig. 4). Be certain to cut the sheet in its valley. Since the edge of this first sheet will not line up with the chalk line of the first row, make a new line half a sheet’s distance from the rake. Now install the remainder of the second row using full sheets and new chalk lines every 44 inches (112cm) for alignment. Lap the lower end of the second row 7 inches (17,8 cm) over the upper end of the first row. Be certain that the center of each lap is over the center of the purlin beneath.
To have all side laps of all rows line up, simply begin the second row with a full sheet and install this and all subsequent rows in the same manner as in the first row (see Fig. 5).
Installing Ridge Caps:
Install all sheets on both sides of roof before laying the ridge. At the ridge the upper end of the sheets should be no more than 2 inches (5,08cm) apart to properly support the ridge cap.
Place the first ridge cap at the end of the ridge away from the prevailing wind, allowing it to project out 3 to 6 inches (7,62 to15,24cm) from the ridge end. Insert closure strip then drive ONDURA nails through ridge piece, closure strip and every Crown (Not Valley) of the underlying sheets. Now cut in 3 to 6” inches (7,62 to 15,24cm) along the crown of the portion of ridge cap projecting out from the end. Fold down the resulting flaps for a weather guard. Position the subsequent ridge caps with a 7 inch (17,8cm) end lap.
Information for Quick Estimating:
- ONDURA Sheets are 79” x 48” (200cm x 122cm)
- ONDURA Ridge Caps are 79” x 19” (200cm x 48cm)
- Sheets needed to cover 100 square feet = 4.5
- End lap each ridge cap by 7” (17.8cm)
- Use 24 nails per sheet
- Use 38 nails per ridge cap
- Closure strips needed: Total the length in inches of the eaves plus twice the length of the hips, ridges, and valleys. Divide the total inches by the 44 (the length of the closure strips) to get the number of closures needed.