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4 common causes of metal roof leaks around screws

Metal roof leaks around screws:

There are lots of contributing factors when it comes to roofing leaks. A properly driven screw will have achieved the following steps and as a result, provide the perfect weather seal.

Driven straight, perpendicular to the material it is fastened on to.

Adequate, clean penetration with no excess swarf protruding or overhanging from the drilled hole.

Driven until the gasket is compressed firmly against the surface.

Below is a list of common causes of metal roof leaks.

1. Choosing an incorrect screw:

Metal roofing screws are usually designed for fixing thin roofing sheets onto steel purlins, trusses or timber underneath. Depending on the thickness of steel underneath, correct drilling point sizes must be chosen in order to penetrate. Most suppliers will provide a list with corresponding drilling capacities to their screws. Read through the list carefully and don’t hesitate to ask questions.

The length of the screw is also important. The length of screw required can be calculated by adding the depth of the roofing sheet corrugation, plus the thickness of the purlin/truss underneath plus at least 2 to 3 full thread lengths to ensure proper fastening. Don’t forget that the thickness of the bonded EPDM washer or Domed BAZ washer should also be taken into consideration.

Thread type should be considered. A rule of thumb is, coarse threads for thinner sheets (<4.5mm), and fine threads for thicker sheets (>4.5mm). This will ensure the fixing to have adequate pullout values against pressure from high winds or snow.

2. Over–driven screws:

The rubber gasket should seat firmly but not over compressed against the surface. The rule of thumb is, the gasket should not be bulging at the sides of the washer flange, or even to the point of being squished. Workers should take extra care while making an attempt to ensure a tight seal between the metal roofing and the screw head because an over-torqued washer loses its elasticity, breaks down prematurely, and oftentimes disintegrate due to over-exposure to the elements.

3. Under-driven screws:

This is an easy one. An under-driven screw does not provide sufficient pressure to the washer to create a firm seal against the surface. This may happen due to incorrect drilling tip capacity selection and therefore could not adequately penetrate the metal substrate underneath to reach the desired depth.

4. Misaligned or skewed drilling:

A misaligned or crooked driven screw will result in the rubber washers not seating properly against the surface, which means insufficient seal of the hole, or one side over compressed, resulting in premature damage to the gasket. Another sometimes overlooked risk is the skewed side of the steel washer or hex washer flange digging in, deforming or sometimes even cracking the surface, which also contributes to leakage.

Some screws have extra features built in to enhance performance; oftentimes poor choice of fixings become the weakest link in a seemingly strong building structure. BDN Metal-Tite® series roofing screws come with an enlarged hex washer flange, anti-static EPDM washer, double thread, Scratshank, and Ruspert anti-corrosive coating.

The large washer flange is designed so that the EPDM washer will remain fully covered after compressed.
Anti-static EPDM washers prevent galvanic corrosion.
The larger diameter upper thread close to the hex washer flange increases pullout values on thin metal sheets.
Scratshank clears out excess swarf, smooths out the drilled hole, and prevents damages to the EPDM.
Ruspert anti-corrosive coating fully protects the screw from weathering and extends the lifespan of the screw and the sheets it is affixed to.

Learn more about BDN Fasteners >>
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How to use self tapping screws for metal?

2021-03-31

How to use self tapping screws for metal?

News

Self-Tapping and Self-Drilling screws are the bread and butter of our business and the most commonly known and used for fastening two different kinds of material, be it steel, timber, or plastic, and the list goes on.

BDN Fasteners offers TIMBER-Tite™ and TRUSS-Tite™ self-tapping screws.

TIMBER-Tite™ screws are designed for fixing metal roofing sheets or wall claddings to timber, whereas TRUSS-Tite™ is designed to fix steel roofs and floor trusses. Basically, all self-drilling and self-tapping screws are able to tap threads, where the main difference is that self-tapping screws normally come with either a blunt head, sharp point, or a reduced drill point.

Blunt headed screws such as the TRUSS-Tite™ is designed for truss components assembly, fixing into steel. These types of steel normally come with pre-punched or pre-drilled holes, and the blunt, slightly tapered leading threads makes it easier to fix the sheets down.

Our sharp pointed TIMBER-Tite™ are designed for fixing roof sheeting to timber. The longer versions such as the T17CG1265C3N or T17CG1250C3N are designed for crest fixing and shorter versions such as the T17H1020C3N are designed for valley fixing. People ask why screws should be fixed down on the crest but not the valley. The main reason being water runs by gravity and flows to the lowest point, and if fixed on the valleys on rooftops, might increase the risk of water pooling around the screws and with time, cause rust.

Shorter self-tapping screws which come with what we call a “reduced” drilling point, provides the same function as a sharp drilling point, but drills faster through thin metal sheeting, and is much more effective at clearing off excess swarf, as it is difficult if impossible to add flutes on smaller sharp pointed screws to due manufacturing limitations.

For roofing sheet fixing screws, always check if they come with a knurled, fluted, or slotted shank, and if the upper threads are larger in diameter compared to the lower threads. You might notice that the majority of BDN self-drilling and self tapping screws for metal are equipped with both. The larger diameter upper threads provide good pullout strength for the whole setup under high winds and the slotted Scratshank design clears out excess swarf which might damage EPDM washers if leftover, which could result in leaks.

Learn more about BDN Fasteners >>

Internal Roof Insulation Installation with Self-Drilling Fasteners
How to use self tapping screws for metal?

2021-03-17

10 Screw Head Types: Different Self-Tapping Screw Head Types

News

Self-Tapping Screw Head Types

A self-tapping screw has the ability to tap threads as it is driven into the material. It is often used only to describe a specific type of thread-cutting screw intended to produce threads in various types of materials, with sheet metal and wood being the most common.

BDN Fasteners offers a range of self-tapping screws. The screws come with either a self-drilling tip for metal or pointed tip for timber. After the tip creates a pilot hole, the thread then taps into the metal or wood the screw is affixed to.

Regarding head types, screws are available in many different head types. Some head types are very application-specific, while others are more versatile for general applications. Head types are usually manufactured according to set standards according to the region used, though some might tweak or even tailer the design here and there in order to meet special requirements.

BDN Fasteners are manufactured according to the tried-and-true Australian AS standards, offering a good balance between cost and performance, and backed with an industry-leading warranty.

10 Screw Head Types

HEAD STYLE	DESCRIPTION
	BUGLE HEAD In the smaller gauges up to 8–gauge, this head style is generally used for plasterboard as it does not damage the face of the sheet. The 14-gauge screws with this head style are often used for landscaping and fixing heavy duty decking boards.
	BUTTON HEAD Screws with this head type are used for stitching thin steel together and the large head provides a good clamping force on the materials being fixed.
	COUNTERSUNK (CSK) HEAD WITH RIBS (NIBS) This head style is used in a broad range of timber applications where a flush finish is required for the fixing, and the ribs countersink the screw into the timber. It also comes in a variety of drive types depending on the application.
	COUNTERSUNK (CSK) HEAD WITHOUT RIBS (NIBS) This head style is generally used with screws that are fixing steel, where a countersunk recess has been pre-drilled.
	FLAT HEAD / FLUSH HEAD This head style is a low-profile type typically used where cladding is to be fixed over the top, including where plasterboard is fixed to a steel house frame. It is imperative that the head sits absolutely flat.
	HEX FLANGE HEAD This head style is used for a broad range of applications including roofing, cladding and timber fabrication, and comes in a range of gauges for heavier duty applications.
	PAN HEAD This head style is used with general purpose fasteners for fixing thin steel to steel or timber substrate.
	SELF EMBEDDING HEAD This head style is mainly used for fixing 3-6mm thick cladding such as Cement Sheet or Blue Board, and the ribs under the head countersink the screw into the material for a flush finish.
	TRIM HEAD This head style is normally used for decking or picket applications where a smaller head is required to avoid splitting the timber when it is installed.
	WAFER HEAD This head style is mainly used for fixing a variety of generally lighter materials to a steel or timber substrate.

Learn more about roofing screws >>
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2021-03-17

How to Master Use of Self-Drilling Screws

News

Self-drilling screws – commonly known as Tek screws – are some of the most widely used metal fasteners in the building and construction industry.

Tek screws or self-drilling screws come with an additional pair of bladed flutes which extends from the threaded portion of the body all the way to the drilling tip. The purpose of this is to combine the drilling and tapping function onto the same screw, thus eliminating the need to pre-drill pilot holes and tap threads. Drill, tap and fasten are completed in one go, saving time and money. The best Tek screws come with various types of surface treatments to cope with the environment and provide weathering resistance to itself and the fastened substrate.

Tek screws are popular for many general sheet metal applications like roofing, cladding, and HVAC, etc.

Larger Tek screws (No.3 Tek and above) are strong enough to penetrate 12~20-gauge galvanized steel, as well as 3/8” to ½” (10~12.5 mm) structural steel and can be used on various civil and naval engineering applications.

What is the best way to use Tek Screws?

To ensure optimum use and extended lifetime, here are some tips and recommendations for fastening Tek screws successfully onto various kinds of metal material.

Choose the right size Tek screw to match the material you are working with.
Make sure that the Tek screw drill point capacity exceeds the thickness of the material to be drilled. Failing to do so may result in burnt out or broken drilling tips.

Power drills with adjustable clutch settings are better suited for use with Tek screws on light sheet metal than Impact drills.
The hammering action generated by impact drills can cause metal dimpling or oil canning deformations on lightweight metal sheets.

Do not overtighten the Tek screw and washer when fastening them onto sheet metal. The washers should be compressed just enough to fill any uneven surface to provide a perfect seal.
Two things can happen if the washers are over-compressed. One, the sheet panel may deform from overtightening, and two, the exposed portion will be exposed to the sun and the elements, which accelerates the weathering process and reduces lifespan.

When fastening Tek screws onto hardened galvanized or structural steel, set your (cordless) power drill clutch speed to approx. 1500 rpm, and apply steady, consistent, pressure throughout the process.
Drill speed exceeding 2300 rpm or more can result in premature drill point wear or burnout, causing it to lose its function.

Do not compromise the quality and workmanship of your construction projects. Your building is only as strong as its weakest fastener. Choose only quality self-drilling screws from a reliable Tek screw manufacturer – Choose BDN Fasteners today, every day.

2020-07-29