How to Build a Low Deck


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In many cases it is much easier to build a very low deck learn to pave a piece of level but waste ground near your house. The waste ground maybe clay fill for example, after a new house has been built, and concrete may be inappropriate and pavers maybe too expensive. Decking is very pleasant to live on as it is warmer, softer and free draining after heavy rain, and is not hard on the eye and bright sunlight. Why not build a pergola to go with it?

The big advantage of decking is that it can be carried around a difficult access, and it’s a fairly straightforward to build for the average home handyperson. A normal deck will have posts concreted in the ground about every 2 metres, then 150 x 50mm bearers are laid on top of the posts and firmly fixed. 150 x 50mm joists are there in laid on top of the bearers, generally at 500mm spacer, and finally the decking is attached to the joists. A deck using this building technique will generally be at least 400 mm high, and all timber will be H3.2 grade apart from the posts which will be H4.

In the case of a very low deck that is only 75-100mm off the ground, then obviously the above building technique cannot be used, it will be necessary to use H4 grade 100×50 for bearer’s and joists. Short post stumps should be used at 1.2m spacing, and set in concrete as per normal. It will be necessary to excavate a channel for each bearer and joist, in the excavated material should either be removed what least kept away from the bearers and joists before the decking is laid on top.

It is a good idea to lay weed mat over the over the deck frame before laying the decking, as this will make sure that no weeds come up through the deck. Laying out the bearers and joists can be a time-consuming process because of the amount of excavation involved, and because the joists need to be butted in to the bearers. However fixing the joists and bearers and posts can be made vastly simpler and safer by using a modern impact driver and 100 mm hex head galvanised screws. While the screws cost $0.30 each the only one is needed at each joint, and they are inserted extremely easily from any angle or position with a good impact driver. The screw is easily removed if the join is slightly off, and a screw can be easily reinserted. This fixing method there’s probably 5 times as fast as nailing, and is also many times safer.

It is very important to build a very strong and level throne for the deck, and while it is hidden in the finished job, any irregularities in level will be very noticeable on the final decking. Once the bearer’s and joists have been completed and the weed mat installed then it is time to lay the decking. This can generally only be purchased in random lengths, so one should expect to have to do some joints at some stage in the process, and you have quite a bit of short decking left over as offcuts. The ideal fixing method is 65 mm stainless steel square drive screws, but the decking will need to be pre drilled and countersunk before the screw is inserted. A modern countersink tool that drills and countersinks accurately is highly recommended, and it is important but the screw was inserted with a low torque setting so that it doesn’t enter deeper than the countersink.