# Let’s Count Screws

Here is an excerpt from Chapter 16 of the Hansen Pole Buildings’ Construction Manual:

Use sheeting screws ONLY on one side of each high rib (See Figure 16-2) with the following exception:

• Roof – each high rib side at Eave Girt and Ridge Purlin (as well as at any end over end splices).

Figure 16-2

Use 1-1/2” long diaphragm screws at eave purlin and ridge purlin, installing one screw on EACH high rib side (unless instructions state otherwise).

If double screws are used at any other locations, there will NOT be enough screws.

Use a diaphragm screw next to each high rib (one side only) on field purlins.  These will be 9” on center, with first screw next to overlap rib.

This language also appears on the blueprints for every Hansen Pole Building which has steel roofing or siding. As not everyone is a reader, a handy diagram is also provided so as to clarify any possible confusion.

Earlier this week, Hansen Pole Buildings’ Shipping Wizard Justine forwarded to me this message from one of our clients:

“This client thinks he is short screws for the roof, would you run a quick count.  He feels he should have received 2618 screws for his building”.

As usual, I start with the premise of we must have done something wrong, so I did a complete breakdown by hand. This client’s particular building is a monitor style (https://www.hansenpolebuildings.com/building-styles/monitor-building-designs/).

Here was the breakdown I provided:  Each wing has 8 rows of fasciae, eave girts & purlins

Main roof has 10 rows

(8 X 2) + 10 + 8 extra (to account for double screws at eave and ridge of four roof planes) = 34 X 51′ of roof = 1734 X 4/3 (4 screws per 3′ width panel) = 2312

At times I am realizing I am not sufficiently verbose in my answers, and I might confuse some clients, as I did this one who responded:

I am unclear about what each of your numbers represent, it looks like this was calculated by linear foot per panel, but that would be incorrect.

1. Plans call for one screw at each raised rib on each purlin, with screws on both sides of each ridge at the eave and ridge.  That makes 8 screws on each end (2×8=16), and 5 screws for each remaining purlin (5×6=30).  That makes the total 46 for each sheet of steel.  There are 34 sheets between the two wings.  34 sheets x 46 screws each = 1564 screws for the wings
2. For the main roof that makes 8 screws on each end (2×8=16), and 5 screws for each remaining purlin (5×3=15).  That makes the total 31 screw for each sheet of steel.  There are 17 sheets on each side of the main roof, equaling 34 sheets x 31 screws each = 1054 screws for the main roof.
3. 1564 + 1054 = 2618 total screws.

Thank you for sending the additional screws, but I do want to clarify both for myself and others, as their method for calculating does not appear to work for all roof designs.”

The client told me where he went wrong – It is FOUR screws for each remaining purlin (36″ width / 9″ o.c. ribs = 4). Somehow he is using (or planning on using) a fifth screw.

The instructions on the blueprints even go so far as to specify the field screws as having four per panel.

The Hansen Pole Buildings Instant Pricing™ system is not perfect, but is pretty darn accurate. Assembling one of our buildings and find something which isn’t adding up? Contact us before it is too late and additional materials are needed to resolve the issue.

# Screw Ridges or Valleys?

Screw Through Ridges or Valleys?

Today’s article is courtesy of the Journal of Light Construction online:

Q: The new corrugated metal roofing on our client’s garage leaks. The installer had driven the fasteners through the valleys and into the 2-by rafters. We’ve since been told that corrugated roofing should always be fastened through the ridges of the corrugation. Which method is correct?

A: Rob Haddock, a metal-roof consultant and director of the Metal Roof Advisory Group, responds: The culture of fastening through the ridge (crest) or through the valley of the metal-roof profile seems to vary in the continental U.S. from one place to the next, from one contractor to the next, and even from one manufacturer to the next. Many years ago (before the advent of weather-sealing washers on fasteners), corrugated roofing was always fastened through the ridges using “lead head” nails. These were galvanized roofing nails with a lead washer under the head. As a nail was driven and its head came in contact with the roofing, the soft lead was supposed to conform to the surface of the roof to provide a seal. But these fasteners were notorious for leaking, which is why they were always driven through the high points of the roofing profile.

Today the fasteners of choice for corrugated roofing are gasketed hex-head screws with a metal and rubber washer below the head. As the screws are driven, the washer presses against the metal roofing to form a water­proof seal. If the screws are driven correctly, fastening through either the valleys or the ridges of the roofing is considered acceptable in this country. Valid arguments can be made for both preferences. If the fasteners on your roof were all properly driven, it is unlikely that they are the source of your leaks, regardless of whether they were driven through valleys or ridges.

No matter whether your installer prefers to screw ridges or valleys, there are several factors to consider when fastening metal roofing to a building. Be sure to choose the right fastener—the right length as well as the right material—for your particular application. Roofing manufacturers often recommend certain fasteners and fastening schedules for their products according to the structural material of the roof. Each fastener must be driven straight into the metal roofing perpendicular to the plane of the roof to ensure that the washer seals evenly around the fastener hole. Also, fasteners should be driven using a properly adjusted torque-sensitive tool to avoid over-driving. Applying too much torque when fastening through the ridges could crush or distort the profile of the roofing, and applying too much torque in the valleys could distort the washer to the point where it no would longer create an effective seal.