Building A Deck Over A Balcony Or Waterproofed Surface

When buildling a deck over a balcony or waterproofed surface, there are some important considerations to be made. As one of Sydney’s leading installers of timber and composite decking, #1 Decks has encountered this issue many times. Here’s our advice for you.

Here’s our checklist to building a deck over a balcony or waterpoofed surface

If you are on a balcony of a block of units, rooftop or there is a water drain in the area you are planning on decking, the chances are the flooring under the tiles has been waterproofed. Now you can deck over the area but we would strongly recommend you don’t drill into the slab to fix the battens down.

With a standard deck that is around 250mm or more off the ground you would use a standard bearer and joist set up. But in most cases with installing decking over a tiled balcony or rooftop you don’t have that much room to fit the framing in. With these lower decks we use battens, which we would normally screw into the slab if it isn’t waterproofed, but we can’t here. So here is a step by step procedure you can follow to ensure you get the best desired result from your decking

  1. First you need to make sure that you have enough room from your desired deck height and the existing flooring, you need more than 50mm for aluminium joist and 60mm for timber joist Measure the width of the decking boards you are using, the standard is 20mm or 19m but there are 25mm aw well
  2. Work our how much you need to pack up your decking to ensure your finished deck height work out right. The thicker joist you can use the better as they can span further, but you must have at least 10mm clearance under the joist and the sub straight.
  3. Cause you can’t just screw your joist down to the concrete because you would puncture the waterproofing, you need to be able to somehow stop them from bouncing & springing. This is where we use EuroTec’s Pedestal Foot. These give you a nice flat surface you can sikkaflex down. They come in all different sizes and they are adjustable so you can get your deck nice and level. You can also screw the batten to through the side of the fin sticking up. Once the sikkaflex holds them down they won’t bounce
  4. Mark out your joist centres at 450mm or less if need be and chalk a line on each joist centre. Lay out all your pedestals along your chalk line with spacing around 1.5m between each one (you can put them closer but they are expensive and you really only need them to hold the deck down and you can use plastic packers to support your battens between them). Glue the base of the pedestal down using sikkaflex once they are in line and in the right position. Its best to let the glue dry so you can work with them without knocking them aroundplug
  5. If you have a laser level go around to each pedestal and level each one to the desired deck height less the thickness of your decking boards and thickness of your batten/joist. If you don’t you will have to use either a water level or 2m spirit level
  6. Once they are all level lay your battens/joists on them and screw them off ensuring they are hard down on the top of the pedestal.
  7. Then all you need to do is pack in between the pedestal with plastic packers if there is spring in the battens/joist
  8. Now you can run your level over the whole frame and ensure its all level.
  9. Make sure you check each joist individually to make sure they don’t have any bounce in them.
  10. Now your ready for laying your boards 

Looking for Help to Install a Timber or Composite Deck?

To discuss the best timber or composite deck for your home or commercial project, request a callback today or call our office on 1300 65 44 78. We are one of Sydney’s leading installers of decking and have a heap of experience to advise you on the best timber, composite or new generation timber product that will suit your area. We work with all manner of properties and budgets.

You can also visit our showroom at 4/29 Bay Rd, Taren Point (click for map).

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