Even though Ondura corrugated products are easy to install, before beginning, you should thoroughly read these instructions to understand how they apply to your corrugated roofing or siding job.

We recommend you have an architect or structural engineer check your roofing plan for soundness and especially for proper ventilation.

Ondura corrugated roofing, like all roofing materials, should be carefully installed. Mistakes in installation can cause roof problems later on. So take your time and closely follow these installation guidelines. As you can imagine, they cannot cover all possible situations.

Tools & Materials

All you need to install Ondura corrugated roofing are the following tools:

• Claw Hammer
  
• Steel Tape
  
• Electric circular saw with carbide-tipped blade
  
• Chalk line
  
• String
  
• Nail apron
  
• Utility knife
  

We recommend a 3" in 12" slope, or steeper, for satisfactory installation of both Ondura corrugated roofing sheets and tiles. For corrugated roofing sheets, these instructions treat a 3" in 12" slope (or greater) with purlins (supports - see fig. 10 for diagram) spaced 24" on center (o. c.); for tiles, a similar slope over solid decking.

For corrugated roofing sheets, this 24" purlin spacing should be reduced under certain circumstances. For example, in areas of heavy snow loads or potential snow drifting on a roof section, purlin spacing should be reduced to 18" or 12" on center. (When in doubt, we recommend that you consider the more narrow spacing. Ondura corrugated roofing can provide you with specific load test data to assist in your planning.) Do not use 16" on center spacing.

On curved roofs, the purlin spacing must be closer in the low slope areas near the top.

Another instance when purlins should be spaced closer is with slopes less than 3" in 12". Space no more than 18" on center at 2" in 12" to 3" in 12" slopes. Also, two-corrugation sidelaps may be advisable.

Wherever extreme weather conditions are possible or buildings have an interior ceiling, solid decking with felt is advisable.

We do not recommend installation on roofs with eave-to-peak distances greater than 80' unless the roof slope is 3" in 12" or more. We do not recommend installation on any roof with less than a 2" in 12" slope. Purlin spacing greater than 24" can cause serious problems and is not recommended.

How to Figure the Number of Corrugated Roofing Sheets You Need

Measure the ridge of your roof in inches, then divide this length by 44" (width of coverage per sheet) to determine the number of corrugated roofing sheets per row. For fractions, round up to the nearest quarter.

Measure the slope in feet, then divide this slope length by 6 feet (length of coverage per sheet) to determine the number of rows. For fractions, round up to the nearest half.

Now multiply the number of sheets per row by the number of sheets for this part of your roof. See example, Fig. 1.

After calculating the number of sheets for each roof area, add all amounts together to find the total number of sheets needed.
How to Figure the Number of Corrugated Roofing Tiles You Need

Measure the ridge of your roof in inches, then divide this length by 44" (width of coverage per corrugated roofing tile) to determine the number of corrugated roofing tiles per row.

Measure the slope length in inches. Subtract 4 3/4". Now divide by 14" to get the number of corrugated roofing tile rows. Round up this number to the next whole row. (The end-lap may be increased and the exposed surface decreased to make the number of corrugated roofing tile rows come out evenly.)

Multiply the number of corrugated roofing tiles per row by the number of rows per slope; then add up the corrugated roofing tiles for each roof area to get the total needed. See Fig 2.

Plan for Adequate Ventilation

Poor ventilation can cause severe heat build-up or condensation which may cause deterioration of roof framing and covering materials.

Positive ventilation, along with additional insulation, can prevent condensation. Figure 36 suggests ways to assist proper ventilation by taking advantage of the corrugated design of Ondura roffing sheets and tiles and by using Ridgeline® Ridge Vents.

We strongly suggest, however, that you check your ventilation plan with a qualified engineer or architect before beginning installation.

CAUTION: Improper or inadequate ventilation will void warranty.

Storage at the Job Site

While stored at the job site, Ondura corrugated roofing sheets or tiles should remain wrapped in their plastic shipping covers. Left outside and uncovered, damage can result from rainwater trapped between corrugated roofing sheets or tiles. Unwrap stacks as needed during installation. Don't allow stacked corrugated roofing sheets or tiles to get wet while stored.

Cutting Ondura Corrugated Roofing Sheets and Tiles

Use a utility knife with a sharp blade for cutting parallel with corrugations, (Fig. 3) or an electric circular saw with carbide-tipped blade for cutting across corrugations. Wear eye protection when cutting.