Lesson 10

Roofing Agricultural Structures

Next Generation Science/Common Core Standards Addressed!

CCSS.ELA Literacy Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions..RST.9‐10.1

CCSS.ELA Literacy.RST.11‐12.3 Follow precisely a complex multistep procedure when carrying out experiments, taking measurments,or performing technical tasks; analyze the specific results based on ex HSNQ.

HSNQ.A.1 Use units as a way to understand problems and to guide the solution of multi‐step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and

Student Learning Objectives/Bell Work

Explain the application of asphalt and fiberglass roofing materials.

Explain the application of metal roofing materials.

Terms

Drill screwsFlashingH-clipsMetal drip edgePipe flashing

collarPlastic cap nailsPurlins

RidgeRidge capRidge ventRing or screw-

shank roofing mails

Rolled roofingRoof vents

Terms

Roofing feltSelvage-edge roll roofingShingleSmooth-surfaced roll roofingStraight blade utility knifeWood shingles

Interest Approach

What kind of roof do you have on your house?

How was it secured down

(nailed, screwed, fastened)?

What is a shingle?

A shingle is the individual roofing unit made of slate, wood, asphalt, or fiberglass.

The shingles used today are almost all three tab seal-down asphalt or asphalt-fiberglass combination shingles.

What is a shingle?

In the early years of this country, most roofs were covered with wood or slate shingles.

The Roofing Process

Regardless of the type of shingle used, roofing starts with the covering of the rafters or trusses with roof sheeting.

The Roofing Process

1st - H-clips are metal brackets shaped like an H installed between each set of rafters where two pieces of sheeting meet.

The clip helps strengthen the joint.

Roofing Process

2nd - Metal drip edge, commonly called T-tin because of its shape, is nailed in place at the outer edges of the roof.

Roofing Process3rd - Cover the sheeting with

roofing felt. Roofing felt is an asphalt

saturated felt that comes in a roll.

Most common thickness used are 15 & 30 lbs. – Straight blade utility knife is a

retractable triangular pointed knife that works well to cut the felt.

Roofing Process

4th - Plastic cap nails are used to nail on the felt.

Plastic cap nails have a one inch diameter cap on a ring shank nail. – When the wind blows, the felt is less

likely to blow off than if regular roofing nails are used.

Wood Shingles

Wood shingles give a natural rustic look to a building but are very expensive and rarely used on agricultural buildings.

Wood Shingles

Usually Cedar or other rot resistant wood is cut in a beveled 16 inch long piece with an approximate ½ inch base thickness.

They are sold by the thousand or in bundles of 250 each.

Asphalt Roofing Materials

Rolled roofing is a three foot wide and 36 foot long roll.

Rolled roofing is not as attractive as shingles and has a shorter life expectancy, but is cheaper.

Asphalt Roofing Materials

Smooth-surfaced roll roofing is used in a single coverage type installation where it is overlapped only a few inches.

Today’s Shingles

Most shingles used today are three tab seal-down asphalt or asphalt-fiberglass combination shingles.

Metal Roofing

Metal has gradually replaced asphalt and asphalt-fiberglass shingles in many agricultural buildings especially when the pole-type or rigid-arch type buildings are built.

Metal Roofing

While metal roofing is noisy in a rain storm and not as attractive as shingles, it is fire resistant, cheaper, and much easier and faster to install.

Metal roofing will be either steel or aluminum sheets.

Installing Metal Roofing

With metal roofing after the rafters or trusses are in place, horizontal nailing boards called purlins. Metal perlins are actually more common in NM.

Installing Metal Roofing

Purlins are installed to attach the roofing sheets.

The purlin spacing depends on the type and thickness of the roofing sheets.

Metal roofing is installed in a particular order.

Installing Metal Roofing

Ridge Cap or Ridge Vent is installed to allow warm moisture to escape.

Metal roofing may be fastened with ring or screw-shank nails.– Ring or screw-shank roofing nails have a lead,

neoprene, or rubber washer to prevent leakage and rings or screws to prevent the nail from popping out over time.

– Metal screws with a rubber washer may be used on wood or metal perlin.

All metal agricultural structures are more common and economical in the southwest US as the metal may be more inexpensive than wood. Metal is often faster to assemble.

Metal roofing is attached to metal perlin using TEK screws.

Lap Screws Perlin Screws

Common Metal Perlin

Comparison of Types of Metal Roofing

While steel sheets are stronger than aluminum they are subject to rust.

To prevent rust,steel can be purchased with a baked on enamel paint or a galvanized coating.

Comparison of Types of Metal Roofing

Galvanized steel roofing comes as corrugated sheets with a zinc coating.

Aluminum Roofing

Aluminum roof sheeting will not rust but is expensive, thin, and easily damaged.

Buildings covered with aluminum must have nailing boards with closer spacing than for galvanized steel.

Corrugated Roofing

Corrugated roofing is made from flat sheets that have been formed into a series of alternate ridges and grooves, or hills and valleys, that run in the same direction.

Corrugated Roofing

The corrugations give the sheets a greater stiffness, increased load-carrying ability, and prevent water siphoning between the sheets into the building.

Review/Summary

What are the kinds of materials used to roof agricultural buildings?

What different practices are used when installing a metal or aluminum roof?

The end!