Deck Inspections
Every homeowner has or has thought of getting a deck installed to enjoy South Africa's great weather. The industry is however wholly unregulated with many poor tradesman out to make a quick buck at the expense and ultimately the safety of people. Internachi estimates that upwards of 60% of the 45m decks built in North America are unsafe because people assume that they are easy to build but they are subject to the same stresses as a home.
The Foundation
Any deck built higher than 30cm above the ground will need a foundation. Unfortunately, when inspecting your deck we will be unable to see the deck foundation as its a visual only inspection but evidence above the ground will point to whether there is a problem. The weight of a deck can be surprisingly high and uneven - if you think of it most people will normally congregate where the rail is located and that is at the very edge of the deck. A concrete foundation for each post is necessary to adequately transfer these loads into the soil below - best practice is to have cast or poured concrete pad that is below the soil line and in direct contact with solid compacted strong soil. The size of the foundation is generally 2ft square depending on the soil. An alternative would be a 'rika' or precast foundation which must be at least a foot below the soil. A good inspector will check how the foundation attaches to the post above - half inch anchor bolts into a metal post base is perfect.
​How many posts should you see? It will depend on the soil conditions and deck purpose, but typically they should be less than 8 feet apart.
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Posts
A professional home inspector will then test the posts for rot - the internet is littered with pictures of failed posts due to rot and insect infestation despite posts being pressure treated. Post size will then be inspected - it should never be less than 4x4 (10cmx10cm). Pictured below is a wholly undersized post, with a poor attachment found below a deck.
Beams, Ledger Board and Joists
Beams (beam is the main load-bearing element for the structural soundness of your deck. It’s not only responsible for supporting the weight of the joists but other building elements as well) should rest on posts and be attached with through bolts with washers on the end. Beams will typically be at least a foot above the ground as they are not pressure treated. If beams are joined, then that join should occur over the post. Picture below is a beam with a materially defective join.
A ledger board is the timber that attaches to the house and will hold your floor joists with hangers. Ledger boards are attached to masonry with bolts in a staggered fashion across the board. 90% of deck failures occur when the ledger board detaches from the house and collapses.
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Joists (Joists are the repeated structural members that are used to build a deck frame) are typically spaced 40cm apart for residential decks and will most of the time rest on the beams. Joists can be toenailed (driving of a nail at a roughly 30° angle to fasten two pieces of wood together) to beams but in high wind areas they should have steel straps to prevent wind uplift.
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A home inspector will check for diagonal bracing if the deck is free standing and post to beam bracing if its above 1.8m.
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Decking & Railing
The deck inspection will then move to the decking where the inspector will ensure that there is adequate spacing between the decking material, that the deck covers at least 4 joists and that it is properly staggered. All screws are typically galvanised or stainless steel to resist corrosion.
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Rails will be inspected with child safety in mind similar to the inspection of a flight of stairs inside a home. Rails will need to withstand high lateral loads as most people will typically lean against them when in use.
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If you are interested in this service please check our pricing and contact us today. We are certified deck inspectors and look forward to your call.
