Product Guides and Tips

Home » Solutions

FAQ – Questions and answers

The most common questions in construction

BDN FASTENERS® Exclusive dealer, distributor and sales offices – Worldwide.

BDN FASTENERS® Sales offices Worldwide

Find your contact person for all BDN FASTENERS® distribution and our partner and sales offices – worldwide.

BDN Fasteners® Building Fasteners Product application

BDN Building Fasteners Product Series

BN3™ Corrosion Resistance Class 3: SST 1000 hrs + Kesternich 7 cycles

– Dual-Edge® METAL-Tite™ Self-Drilling Screws Series
– TIMBER-Tite™ Self-Tapping Screws Series
– Framing Screws Series
– Polycarbonate Roof Fasteners Series

C3 & C4 Surface Coating Corrosion Warranty

The below table is an indication of the warranty period based on the corrosivity of your location and is to be used as a guide only. To determine the appropriate ISO 9223 category for your environment, please contact your local representative. Environmental conditions and category is complex and can be influenced by a wide range of factors. Note that in certain instances, corrosion zones can extend out further to what is stated above.

Class 3 & Class 4 Surface Coating Corrosion Warranty

BDN Fasteners® has aligned the warranty period for its products to be consistent with the warranty period of major roofing material suppliers. AS3566.2 Outdoor Exposure testing results indicate the lifespan of our products to extend beyond the warranty period.

Fastener Corrosion Resistance Classification

CLASS 3: Withstand 1000hrs Salt-Spray Test (SST) + 15 Kesternich Cycles [Condensing the atmosphere containing Sulphur dioxide (SO2) at level SW 2.0 S – Simulates acid rain or industrial chemical exposure to evaluate the relative corrosion resistance.]
Class 4: Minimum Porosity Rating of 8 (Micrograph comparison). 45 um of 98% Zinc composition on hot-dipped galvanized coating. 25~30% of Tin balance zinc composition on Mechanical Zinc-Tin plating.

Fastener Corrosion Resistance Class 3 & Class 4

POLY-FAST Polycarbonate Fasteners Installation Procedure

POLY-FAST™ roofing fasteners feature a Thermal Expansion Hole Cutter that creates a much-required thermal expansion hole on plastic profiled roofing panels, The panels are then securely fastened onto the purlin support underneath in onego.

POLY-FAST Polycarbonate roofing Fasteners Installation Procedure

A nominal 11mm diameter hole is created by the Thermal Expansion Hole Cutter during the process. When mated with the Thermal Expansion Hole Cutter, with the Depth Stop Knurls acts as a stopper, the height at where it stops upon coming in contact with the purlins; enough so that it prevents screw over-run or over-drive, provide a perfect seal to the enlarged hole, but not deform the corrugations. BDN Fasteners polycarbonate roof fasteners are designed to create precise thermal expansion holes for fixing polycarbonate roof sheets.

Fast Plastic Roofing Fasteners (For Timber)

Fast Plastic Roofing Fasteners ( For Steel)

4 common causes of metal roof leaks around screws

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

1. Choosing an incorrect screw

2. Over–driven screws

3. Under-driven screws

4. Misaligned or skewed drilling

Roofing Screws-BDN Fasteners-Made in Taiwan

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.

Eco-BDN, Green EPDM Washer Installation Guide

Eco-BDN, Green Washer - BDN Fasteners

Building it right to make it watertight

Eco-BDN, Green EPDM Washer provide an excellent waterproof seal— even under the most severe weather conditions— if properly installed.

The trick is not to overdrive or underdrive the screws.

If the screw is not tightened enough, moisture leaks around the washer. An overtightened screw squishes the washer too thin, which can also result in leaks.
Important Tip: Replace worn sockets immediately if they cause the screw to wobble during installation. Crookedly driven screws can cause water leaks.

Screw Installation Guide

BDN POLYXPAND™ BAZ EPDM Washer Installation Instructions

BAZ EPDM washers are the ideal washers to be used on polycarbonate sheets, especially corrugated ones. With a large diameter to fully cover expansion holes to provide the perfect sea and flexibility to conform to the curvature of the skylight, but at the same time, providing enough strength against high wind situations.

However, it is absolutely critical to not drive the screw to the point that the washer is squished, which will result in the washer losing its flexibility, and a gaping hole gouged out by the hex washer flange.

Self-Tapping vs. Self-Drilling Screws: Do You Know the Difference?

Self-Tapping vs. Self-Drilling Screws:

Do You Know the Difference?

Self-Drilling Screw – Steel Sheet / Steel Purlins

Trident Drill Point
✔ Improved Drill Performance
✔ Time Saving

Self-Tapping Screw – Timber

Type 17 Sharp Point
✔ Reduce Splitting

Patented Trident Drill Point

The patented Trident Drill Point provides fast and

steady drill performance, effectively clears swarf,

and drills through 6mm thick steel.

“S” Swirl: Creates a larger area of engagement from the initial drill drive.

Improved “Cutting Edge” Design: Larger, curved cutting blade edge lower manual load required.

Incorrect screws create stress cracks and thus leakage on Polycarbonate or other Plastic Sheets

BDN Fasteners® POLYXPAND™ (Skylight Fixing Fasteners)

True Australian AS3566 Standard Hex Washer Flanged Head:
Separate EPDM steel bonded washer NOT required. (No risk of leakage)

Thermoset 100% EPDM BAZ washer:
☑Weathering Resistant (UV / Ozone / Acid)
☑100% Leak proof sealing
☑Perfect fit under hex washer flange
☑Optional metal washer add-on
☑Shock absorbing (for high wind areas)

Creates a 10mm dia:
Thermal expansion hole for plastics.

Winged Drilling Tip:
Wings break off once in contact with the steel purlins,
keeping the plastics sheets securely fastened.

BDN Fasteners Surface Coating Class

Here at BDN Fasteners, we have categorized the kind of environments to the following based on its characteristics. Scope of warranty for our products are also based on the category the environment is classified to.

Dry, Rural Areas – Areas remote from the coast and sources of pollution; as well as all of the areas listed below.
Mild Urban or Rural Areas –
- Areas with little to no chemical pollution, including but not limited to natural chemicals such as ammonia from livestock or carbon monoxide from log-ﬁre.
- Areas far from the coast with no impact from salt water spray.
- Areas at least 2 kilometers away from any type of industry, light or heavy.
Light Industrial or Urban Areas
- Light industrial zones, light manufacturing, warehousing, distribution, or limited light intensity activity areas.
- Built up areas constituted of high human population and infrastructures.
- Areas at least 1~2 kilometers away from light industrial or urban areas.
Small Industrial Zones
- Areas located in or adjacent to small industrial zones.
Coastal Areas
- Areas located approximately 2 kilometers from the coast.

BDN Fasteners – Surface Coating Class

Corrosion Resistance

Class2 – SST 500hrs + Kesternich 5 Cycles
Class3 – SST 1000hrs + Kesternich 7 Cycles & 15 Cycles
Class4 – SST 2000hrs + Kesternich 15 Cycles

✓ Australian AS3566 Standard
✓ SGS Certified

True Australian Standard-AS3566

The BDN Comparison-AS3566

BDN Fasteners

True Australian Standard-AS3566

Washer Diameter=13.97-14.78mm

Scratshank

SCRATSHANK FEATURES

Cutting / Break out the metal filings
Remain free of damage to sealing washer during installation
Weatherseal

SCRATSHANK, Clear/Break out metal filings - BDN Fasteners

Double Scratshank: Swarf Free

BDN Fasteners – Dual-Tite™ (Roofing Screw Duofix 2 IN 1)

Double Scratshank: Removes sealing washer damaging swarf during installation.

Harpoon Thread: Anti-stripping, roof fixing threads

BDN Fsateners – Dual-Tite™ (Roofing Screw Duofix 2 IN 1)

Harpoon Thread: Anti-stripping, roof fixing threads

BDN Fasteners 100% Weather Sealed

DEKS Dekseal® Trueblue® 100% Weather Sealed

BDN Fasteners – B//> Series: Silver Blue / SST 5000hrs / Kesternich 5 Cycles

Hex Washer Flange: True Australian Standard-AS3566
DEKS Dekseal® Trueblue® 100% Weather Sealed
100% Made In Taiwan

BN3 Series - DEKS Dekseal® Trueblue® 100% Leak proof sealing

BN3 Series – DEKS Dekseal® Trueblue® 100% Leak proof sealing

BDN Fasteners – BN3 Series: Silver Grey / SST1000hrs / Kesternich 7 Cycles

DEKS Dekseal® Trueblue®: 100% Weather Sealed
Hex Washer Flange: True Australian Standard-AS3566
100% Made In Taiwan

4 common causes of metal roof leaks around screws

News

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.

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 >>
Internal Roof Insulation Installation with Self-Drilling Fasteners
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.