COATING

ELECTRO-ZINC COATED SCREWS DOES NOT CONFIRM TO STANDARD AS3566CLASSIII AND ARE BEST SUITED FOR INTERIOR APPLICATION ONLY. DOES NOT CARRY ANY RUST PROOF WARRANTY. WILL FAIL ACID TEST.

HEAD

ELECTRO-ZINC SCREWS HAVE SMALL HEX HEAD AND USE OF EXTRA METAL BONDED WASHER IS COMPULSARY.

THREAD

ELECTRO-ZINC PLATED CREST /PROFILE SCREWS ARE FULLY THREADED. DOES NOT HAVE DOUBLE SIZE THREADS TO HOLD THE CREST UPRIGHT. THERE IS A CHANCE OF CREST GOING DOWN WHILE WALKED ON ROOF AND CHANCE FOR WATER LEAKAGE.

SHANK PROTECTION

DOES NOT HAVE ANY FEATURES FOR SHANK PROTECTION.. THE ZINC COATING BELOW THE PROFILE IS RIPPED OFF WHILE DRILLING THE SCREW AND IT IS WHERE THE RUSTING STARTS BECAUSE THERE IS NO COATING TO PROTECT THE SCREW.

THE CORRECT METHOD FOR FIXING A ROOF SHEET IS CREST FIXING AND NOT VALLEY FIXING.

IT HAS BEEN NOTICED THAT TO SAVE COSTS ON INSTALLATION VALLEY FIXING IS DONE, BUT THIS IS A VERY SERIOUS AND DANGEROUS SITUATION.

DURING RAIN, WATER FLOWS THROUGH THE VALLEY [PAN] AND FIXING SCREWS ON VALLEY CAN OBSTRUCT THE FLOW OF WATER,AS THE VALLEY IS NOT CLEAN,IT HAS DRY LEAVES,DUST AND INDUSTRIAL FALLOUT DEPOSITED ON IT. THE CONSTANT FLOW OF WATER MAKES THE VALLEY SCREW WET ALL THE TIME AND THE WATER STAGNATION HELPS IN SEEPAGE OF WATER THROUGH TINY GAPS AROUND THE SCREW.

WITHIN TWO RAINS THE SCREWS ON VALLEY WILL START RUSTING AND THIS SITUATION GOES UNNOTICED UNLESS THE SHEETS STARTS FLYING ON A WINDY DAY.

HENCE IT IS ALLWAYS ADVISABLE TO DO CREST FIXING ON A ROOF,JUST TO SAVE SOME COST WE CAN NOT BE RISKING THE WHOLE ROOF.

Those who think that self-drilling fasteners (or more commonly known as roofing fasteners) are the least important part of their entire steel building are severely wrong. If you think about it, the self-drilling fasteners (SDF) are the ones that pierce holes into the sheets covering your building. Whether the application is concealed or exposed, this opens your building to potential problems like water leakages, pre-mature corrosion and even your sheets being blown off in the event of strong winds.

Several people have the tendency to neglect this particular fastening requirement in steel building construction. Normally constituting only about 1% ~ 2% of the entire building cost, owners of the building, architects and engineers find it either too trivial an item to take notice of, or are totally not bothered about it. While irresponsible roofing contractors will rejoice with one less criteria imposed upon them, owners of the building are entirely blinded.

In simple logic, if you are using premium sheets with wrong quality of SDF, it is like tailoring a suit using high quality fabric with poor quality thread where in the end, the seams are just waiting to burst or fray.

Just a general comparison of the performance of Zinc plated (3 ~ 6mu) SDF versus one that complies with Class 3 standard (Class 3 standard is explained below). The Zinc plated SDF would fail the Salt Spray Test within 45hrs while the latter lasts till 1,000hrs and beyond. There is obvious difference in the corrosion resistance of these two types of SDF. At least by 20 fold, actually.

WHAT IS CLASS 3?

So how does one know that they are purchasing SDF of the correct quality? AS 3566 established by Standards of Australia is one standard SDF manufacturers should use as a guideline to gauge the corrosion resistance of their fastener’s coating. Separated into various classes, each class determines the level of corrosion resistance and the recommended environment to be used.

For the general outdoor application of SDF, Class 3 standard is recommended as the minimum classification of corrosion resistance. The Standards of Australia calls for SDF meeting Class 3 classification to pass the following tests:

1.1,000hrs of Neutral Salt Spray in accordance with AS 2331.3.1
2.1,000hrs of Relative Humidity in accordance with ASTM D2247
3.2,000hrs of UV Condensation in accordance with ASTM G154
4.15 cycles of Sulfur Dioxide (At level SFW 2.05) condensing atmosphere in accordance with DIN 50018

Suppliers of genuine Class 3 SDF should be able to show you test reports for the above FOUR tests. Any one less report, you should be wary of the integrity of their product. These test reports should also be produced by internationally accredited laboratories rather than in-house. Better still if the suppliers can show you a series of reports showing that the testing is constantly being updated.

Some manufacturers in the market are even willing to produce a factory warranty for the SDF sold. Assuring buyers against pre-mature corrosion of their SDF.

DRILLING EFFECTIVENESS

Perhaps another factor that is greatly neglected by many is its drill effectiveness. The design of the drill point determines how easy and fast it is for the contractor to install your sheets. A poorly designed drill point requires more effort to fasten into the sheets and hence have a high tendency to affect workmanship. This is the common starting point to your leakage problems. A quality SDF manufacturer would have taken the design of their drill point as seriously as the corrosion resistance itself. Such manufacturer would also be able to provide you with drill test results as a basis of comparison.

To the builders, a more effective drill point would translate to higher standards of workmanship and lesser man-hours required to complete the same job.

NO ROOFING CONTRACTOR/SUPPLIER/ROLL FORMER OF COLOUR COATED ZINCALUME/GALVALUME SHEETS CAN EVER WARRANTY HIS PRODUCT IF SELF DRILLING SCREWS CONFORMING TO AS3566 CLASSIII ARE NOT USED WHILE FIXING THE SAME.

THE REASON IS SIMPLE! IF AS3566 CLASSIII SCREWS ARE NOT CHOSEN, THE SCREWS WILL START CORRODING AND WILL DESTROY THE ROOF SHEETING AND STRUCTURE IN A VERY SHORT TIME

ROOFING SCREWS COSTS JUST 4 TO 5% OF THE TOTAL ROOF COST, BY CHOOSING A SCREW NOT CONFORMING TO AS3566-CLASSIII THE BALANCE 96% OF THE ROOF INVESTMENT IS AT RISK!

HENCE IT IS WISE TO USE A AS3566 –CLASSIII COMPLIANT SELF DRILLING SCREWS FOR ROOF FIXING AND WALL CLADDING.

THE AS3566 IS A STANDARD ESTABLISHED BY THE STANDARDS ASSOCIATION OF AUSTRALIA TO SPECIFY THE REQUIREMENTS FOR A SELF-DRILLING SCREW TO BE SUITABLE FOR USE IN STEEL AND TIMBER. IT CLEARLY SPECIFIES CERTAIN CRITERIA THAT A SUITABLE FASTENER SHOULD MEET. ONE OF THE MOST IMPORTANT CRITERIA OF THIS STANDARD COVERS THE CORROSION RESISTANT REQUIREMENTS OF A SELF-DRILLING SCREW. THIS CORROSION RESISTANT CRITERION HAS BEEN USED BY SEVERAL MAJOR MANUFACTURERS AND CONTRACTORS OF METAL ROOFS AND STEEL BUILDING STRUCTURES AS THE MINIMUM STANDARD FOR ANY SELF-DRILLING MANUFACTURER TO ACHIEVE IN ORDER FOR THEIR FASTENERS TO BE FIT FOR USE WITH THEIR STEEL STRUCTURAL PRODUCTS.