Polycarbonate sheets have the versatility and the clarity needed to take any home improvement project to the next level. Clearly, home improvement projects need to have a level of diversity in order to break through the boundaries of traditional home improvement constructs. Also polycarbonate sheets are 250 times stronger than traditional glazing! Because of this they are the choice for greenhouses, and windows for sheds.
If DIY projects are your thing, despite polycarbonate sheets being shock resistant, the installation has to be done a very particular way in order to achieve the best results. And in order to achieve the best results, avoid being rough DIYer (which results in cracks and large fractures in materials).
With this in mind, we deliver to you a detailed step by step guide to installing polycarbonate sheets, and to avoid the pitfalls of cracking. Crystal clarity and structural soundness for years to come!
Material Science: Why Polycarbonate Develops Cracks
Before we talk about preventing cracking, we need to talk about the material’s physics. Polycarbonate is a type of thermoplastic. Polycarbonate is very different from glass in that it has a very large coefficient of thermal expansion. This means that it expands when heated and contracts when cooled. It does this more significantly than the timber or metal frames it is typically attached to, and can lead to cracking.
Some causes of cracks include:
Movement Deficiency: The sheet is pinned too closely. This causes buckling, and cracking, of the sheet when it is attempting to expand.
Misguided Tooling: The use of incorrect drill bits, or blades, can lead to micro fractures that will expand over time.
Phase 1: Preparation and Tooling
Preparation is the stage where I can determine 90% of your success. Before peeling back that protective film, I want to make sure you have the tools.
1. The Proper Saw
If you will be cutting your clear polycarbonate sheet on site, use a fine toothed circular saw, or a jigsaw with a plastics specific blade.
Pro Tip: Avoid the use of a coarse wood blade. Big teeth will grab the material and cause vibration, which can result in shattering along the cut.
2. The Secret With Drill Bits
Metal drill bits are created to bite into materials. When drill bits bite into polycarbonate, they can cause something called the polycarbonate sheet to climb the bit, which can cause a crack.
The fix: use a drill bit that is made for drilling plastics (has a flatter tip) or filet a standard bit by using it to drill into concrete. When drilling, support the sheet with a piece of scrap wood to avoid a blowout crack when the bit exits.
Phase 2: The Installation Process (Steps 1 and 2)
Step 1: Measure Correctly and the “Expansion Gap”
This rule is the most important when it comes to polycarbonate installation, always, and I mean always, leave room for the sheet to breathe.
The Rule of Thumb: For every linear meter of the material, leave a 3mm – 5mm gap on all edges.
Why?: a 3 meter sheet can expand by several mm on a hot summer day. If it gets trapped by the frame with nowhere to go, it will bow and crack at the fixing points.
Step 2: Pre-Drilling the Fixing Holes
You cannot, at any circumstance, use self-tapping screws as you go through the sheet without pre-drilling.
The Technique: If you use a 5mm screw, then the hole you drill in the polycarbonate should be 7mm or 8mm. This is because you should drill a hole 2 to 3mm larger than the screw. This will create a “floating” fixing that allows the polycarbonate sheet to slide under the screw head as the temperature changes.
Step 3: Making Sure You Have the Right Fixings
Epdm bonded washers, also known as selascrews, or “mushroom” fixings have large washers. Use these.
Why? Because these large washers spread out the load and help to ensure the fixings do not cause cracking.
How tight? It should be tight enough that the washer is against the sheet but not so tight that the sheet starts to indent.
Step 4: Glazing Bar System (The Professional Choice)
For roofing projects like carports or patio covers, we highly recommend using a Glazing Bar System rather than fixing screws directly through the material.
How it works: The rafter gets a fixing put into it, and then the clear polycarbonate sheet gets “sandwiched” between rubber gaskets.
The Benefit: Friction and gaskets hold the sheet firmly, yet it is not “pinned” by a screw. This almost completely alleviates the possibility of cracking, because the material can expand and contract along length of the bar.
Phase 3: Evading Chemical Fractures
Many DIY enthusiasts notice cracks forming a few weeks after what they thought was a successful installation. This is due to what is often referred to as “Environmental Stress Cracking” (ESC).
Polycarbonate reacts with certain standard DIY products, especially the chemicals.
Sealants: Standard acetoxy (vinegar-smelling) silicone should be avoided. The acetic acid in it will, in fact, damage the polycarbonate. Use Neutral Cure Silicone or an adhesive meant for polycarbonate.
Cleaning: Ammonia and alcohol window cleaners should be avoided. Lukewarm water with a touch of a mild detergent and a soft microfiber cloth will do just fine
Specific Use Cases: Greenhouse and Shed Windows
The process is a bit different if you’re swapping out shed windows or greenhouse panes for clear polycarbonate.
Glazing Clips: For greenhouses, “Z” or “W” clips. These offer adequate spring tension to keep the pane in place without forming a hard, fixed point.
Beading: In wooden sheds, use wooden beads and a bead of neutral-cure silicone. Make sure the bead is not nailed down too tightly so that it doesn’t “pinch” the sheet.
Checklist for a Crack-Free Installation
- Support the Material: Cutting requires the sheet to be flat to avoid vibrations.
- Leave the Film On: You should keep the blue or clear protective film on until the last moment and at all costs to avoid scratches.
- Check the UV Side: Most clear UV polycarbonate sheets are only UV protected on one side. Ensure the film printed side is the one facing the sun.
- Oversize the Holes: Ensure that the screw holes are all bigger than the screw.
- Use the Right Sealant: Only neutral cure silicone.
Why Choose Wholesale POS for Your Polycarbonate Needs?
Why would anyone choose Wholesale POS for polycarbonate products? Because it represents clear polycarbonate sheets and the knowledge that will make your project work. Do you need custom cut sheets for a POS display or resistant glazing for a structure outdoors? With top grade CNC technology, our people make clear edges and stress free glazing, minimizing cracking from day one.
Are you ready to undertake a new project? Take a look at our Polycarbonate Sheets and get the right cut for your project.
While not complicated, installing polycarbonate requires a different way of thinking. With understanding and respect for the material’s need to move and the appropriate drilling and cutting methods, you get to enjoy a timeless, crystal-clear, shatterproof finish.
Helpful Final Tips: Always measure twice, drill wide, and never over-tighten.
