Tag: Corrugated

This article is regarding using polycarbonate (henceforth called PC) sheets for roofing or other applications, in the Indian market, as of June 2025.

    It is well known that Polycarbonate is generally much stronger than glass and as a roof, if installed properly, would last for 8-12 years without any issues. The good thing is that the PC sheet pricing has come down or remained the same over the past decade or so, due to better manufacturing and more manufacturers.  Price differentiations between different manufacturers are not much either.

    A few brand names are known for their PCs – Lexan by Polyvantis (earlier it was General Electric GE and then Sabic), PC Lite MG Polyplast, Ultralite and Poly Mac by Saraswati Plastopack, Lotus roofing, Natlite by Jaichittra and Palsun and Sunlite by Palram which had acquired an Indian company called Tuflite earlier. There are many more mass markets lesser-known-branded or unbranded sheets available in the market that are used more massively as I believe there are no obvious differences in the product, other than superior manufacturing which may not be that transparent to the customers.

   When it comes to roofing, a few alternatives are there in Polycarbonates – Multiwall starting with the most common Twinwall, Solid Compact sheets, Corrugated sheets and Embossed sheets. The PC sheets come with various thickness and depending on the place you reside, you need to investigate the thermal strength and the light transmittivity the most. The Clear sheets in all these usually transmits the most light through it. And lighter the thickness, more the light that passes through. The strength barely fluctuates with varying thickness. The thinner the sheet, more the noise generally if rain hits on the top. 

    Polycarbonate is not just strong but is also highly effective at blocking UV rays.   About 10% of the radiation generated by the sun is UV. Most polycarbonate sheets come with a co-extruded layer that provides UV protection, filtering out over 99% of harmful UV radiation. This layer can be about 50 microns or above but does gets thinner due to constant radiation and may be ineffective to block UV after a few years.  A handful advertise to having this UV layer on both sides, but it is good enough to have it on the sun-facing side. Unfortunately, the starting model 9030 of Lexan does not have any UV coating although they charge you an arm and a leg for it, but only their ExcelD has it.  Ultralite has UV protection in both sides whereas PolyMac has only on one side, when it comes to Saraswati sheets, just to name a few.

   Then you have a different variety of the same called Multicell which is mostly sold as a high-end product for day Lighting – they are usually of 16mm thickness and above and not like the square cells of multiwall but rather than a beehive V formation inside. They are called panels as they have a protrusion to fix them against the solid structure and a cap on top of it giving it a good watertight finish. Due to their thickness and nature of the sheet, unfortunately the light transmission is much lesser and closer to 60% for clear multicells. But this does give you a better watertight roofing alternative with end tapes and end caps.

  A good Silica sealant is important after screwing the sheets on the frame.  If you have it placed on a frame between two walls, it is a good idea to groove the concrete a little so that you push the sheet into the groove and apply sealant on it. If you are on a frame without walls, the end side must be closed properly with a U or a F Channel.

  Since the sheets costs a lot, especially the solid compact one, it is better to ensure you have an idea how to place the sheets and then try to find our how many sheets you need. Remember since the solid compact is much heavier than the multiwall sheets, the frames on which they sit should also support it properly. Also, the cost of the solid is about 3x to 5x of a Twinwall – so it may be product for you to buy the Twinwall and even though their longevity is lower than the solid compact ones, it is better to replace them after a few years.

  Remember, just because a particular brand is available in plenty in the market, does not mean this is the best.  Usually these are the cheap mass-produced sheets coming from some a generic manufacturer who will not even provide the specification of it.

Word about installers in India:

• The guys who would install just the sheet would be ideally a metal fabricator who do the underlying Mild-steel frames too. 
• Most of them do not do labour only although they charge you an arm and length unreasonably.  If you give them the entire thing including sourcing the sheet and the accessories, then their margins are so high which they lose if you buy the sheet.
• Installers do not care about the wastage – you do as you would be paying for it. So, you do the homework first and influence the installer accordingly
• Most of them also do just the basic fitting and barest minimum – remove the old sheet (if you are replacing), cut the sheet to size of frame, screw it and apply sealants – no other stuff.  You would find them very hollow in their design thinking and get offended if you try to add some design ideas to their installation
• None of them use Aluminium tapes or Vent tapes for Twinwall installation- it is good to have them so that the moisture and dust does not get in.
• If it is just on a frame, the installation would hardly take couple of hours.  If it is within a wall and sitting on a frame, add another hour
• Although there are Polycarbonate connectors for H Profile and U profile available which are more aesthetically appealing, they are not easily available in India except a few vendors in the NCR region, most of them use Aluminium connectors for the same
• Installers generally act busy and never would come for a small installation. If they come, they would ask for the big installation labour – just a mentality thing. In my case, couple of them acted so busy pretty much stating take it or leave it and not to bother them – just plain rude as they do not care about losing your business. Just like the auto drivers here who would rather sit and while their time rather than taking customers to short journeys.
• Most of them do NOT know their job – it is very easy for one to do as DIY – enough instructions available online and tools are easy. You just need an additional hand for installing due to the size of the sheet involved and carefully cutting, placing and screwing. All you need is a concrete grinder, a sheet cutter, a screw drier and a sealant gun.
• If you are replacing the sheet, no installer cares about close the holes left by the screws of the old sheet on the frame you use – you should close them before you screw the new sheet in another location of the frame. And if you want to reuse the old sheet for your garden or anywhere else, let them know about it upfront.
• Check around for the best waterproof sealant for your application – the installers would get you some no-name sealant only. Same with the sheet – if you let them buy which is one reason, I do not allow them to, they go after the generic makes stating everything comes from the same factory and not some good brand names like Lexan or Palram who have a good web presence. Most of the sheets available in the market do not even have a specification document that you can find, even the manufacturers do not post them on their website.
• Each installers installs them differently – none use U channel or Al frames or even grooves. So, ask them before you start using their services.  They do just plain vanilla work
• Ensure they guide you to use H frames if you are joining two PC sheets together and using U or F connectors at the end.  Using H frames would save you lots of leak problems at the border where the sheets join.  They would just use sealant without the H profile and if you big them hard, they would just install an Al beading on top of the joint. Always use a rubber gasket inside the connectors before they use them.
• If you are using U profile or a F connector at the slope ends, ensure there is a one mm gap so that the connector does not touch the vent or Al tapes you would have installed, so that there is some escape of moisture.
• And never have an installer guide you about what sheet or sealant to put for your purpose as they would suggest what is easy for them to install.

Word about the manufacturers in India of Polycarbonate sheets:

• It is important you get to know their manufacturing process and what resins they use and about the UV protection layer on the sheet.
• As I told earlier, many do not even provide specification of their sheets online or anywhere even if you ask them by email or WhatsApp. The most important specification you would need for roofing purposes is the light transmittivity, bending radius and their (tensile) strength. For skylights into your house, you need to have a transmission of a minimum of 80%.  For skylights in malls and commercial, may be 65% would be OK.  The strength does not vary much compared to thickness.
• Surprisingly none of the manufacturers carry the connectors that go with installation nor even the screws that they would recommend. Ideally the screw length should be the sum sheet thickness and 50% of the frame thickness, and one should get only the Stainless steel or a more expensive brass screws with washers as they do not rust easily.
• Most of the manufacturers do not even give you details of their manufacturing process to get confidence on their products.
• Talking to Palram or Lexan directly, they would not even bother answering your queries or solve your issues especially if this is not a large commercial business for them.
• Due to their die size and manufacturing process, only certain lengths are available in the market – for a solid compact PC sheet, it would be 4 ft x 8 ft and for a multiwall (rather twinwall for most of the thickness) they come in two widths, 4 ft and 7 ft and a standard length of 39 ft approx.   This limits your purchase as you need to plan for wastages which can be high.
• Manufacturers or the top distributor for the region never would sell cut lengths – they would sell a full roll of 39 ft for Twinwall. What would a residential owner do with a full roll if his needs are only quarter of it? It is easier for the dealer to sell the rest after cutting to another customer, is it not?
• Check for UV protection on one side or two sides. Put the UV protected layer on the top facing the sunlight. Since this is an additional layer they extrude, these microns would erode over years, and you may not get any UV protection after 5-7 years or so.
• In these times of 3D printing, it would be great if some manufacturer is able to turn around a particular size quickly and send it to the customer within couple of days straight from the factory. Supply chain becomes important as this is Just in Time manufacturing. This is mostly wishful thinking in India, as most of the market is controlled by the local distributor and the local dealers.

Polycarbonate (Twinwall) installation process:

1.  First, if you are placing your old sheet, find out where the old holes are, take a photo, and see how the top part is fixed on or above the wall. Check for grooving on concrete where the sheet was place.  Ensure you understand where the old holes were as it would be painted upon. Do not drill in the same place.

2. Remove the old PC sheet carefully without breaking – to be used for gardening and other purposes

3.  Remove all debris and old sealant off completely and clean the walls of dust, of edges and MS Frame

4. Using machine, cut a groove into the two or three walls that is deep enough, if you need it.  If you are putting a U frame around the sheet, this may not be necessary.   Remove the dust. Wipe the frame properly now.  Even with Grooving, although the sheet can be set inside, there is still a chance for the sheet corners to leak after a good rainfall.

5.  Apply metal paste on all old holes and close it. Let it dry.  Mark the old holes. 

6.  Paint the MS frame from all sides. Let it dry.

7.  Apply sealant/concrete paste between the walls and the frames to close all gaps properly.  Let it dry.  

8.  Cut sheet by placing on top itself with actual measurement, including the groove and fit it properly. Make sure there is no leakage from the top – placement on top is important.  There should be a small tongue on the side for overlap, if you have one.

9.  Apply 2-inch Al adhesive tape on the sheet edges on all three sides.  Or on the top side. Attach the 5 ft U cap to the top width side and apply sealant on both sides

10.  Attach the U cap on the two length sides, cut properly with the hole in the overlap section.   If you are setting it up against the groove, then no need for a U Frame but after installing the sheet, it would be better to put a 2-inch Al thin beading on the corers

11.  Screw on the corners (1.5 inch away from the wall) and apply clear Silica sealant between the wall and the Al U frame, and then sealant on the edge of the frame to the sheet. 

12.  Make 3-4 small holes for vapour escape on U cap. Attach the 5 ft U cap to the bottom with 1 mm gap between the edge of sheet and U cap.   If vent tape is available, put this one first before you do the U cap.

13.  Screw in all places and apply sealant on top of the screw. For any overlap section, may be one needs a longer screw.    Apply a dot of sealant on top of all screws to ensure there is no holes that rains can come through.

14.  Apply a waterproof transparent or Al tape on the top side between the wall the sheet so that rain does not come through.

15.  Put the Transparent waterproof tape on the length sides between the wall and the sheet. 

     IN short, polycarbonate market is not mature in India and is not a flourishing one. PC is used only for odd jobs and that too the cheapest solid 2- or 3-mm compact sheets, the alternatives being Glass and Acrylic.  No manufacturer has an end-to-end service from selling to installation which is unfortunate but may be a good business opportunity for one who wants to take the risk. PC beats Glass anytime in strength and does not break easy, especially if you have a done a good frame underneath.   Almost all PC would turn yellow from white over a few years and one needs to replace it, hence the manufacturer does not want longevity in their sheets but may be under designing them for replacement market.   IN short, if you are a homeowner, getting to install a PC is hard and takes time.