Deck footings: Installing deck footings

deck footingsWhen using timber deck posts, it is highly recommended and considered best practise to connect your timber posts to the deck footings using a metal stirrup or bracket. Installing timber deck posts directly into concrete deck footings will encourage dry rot in your posts. This is outlined in our “15 Most Common Deck Construction Mistakes” report.

The image to the left is a very poor example of installing a stirrup into a concrete footing. When you install your stirrups into your concrete deck footings you need to keep the top cross bar (this is what your timber post sits on) above the top of the concrete footing by 75mm. In this example the builder has not installed the stirrup deep enough into the concrete footing leaving much larger gap than 75mm. In an attempt to repair the incorrect installation, the builder has added extra concrete around the stirrup. You can do this is some instances, however you need to maintain a minimum of 50mm of concrete around the stirrup and keep the top of the concrete below the bottom of the post by 75mm. As you can see this never happened in this example. To learn how to install deck footings correctly you can purchase your own copy of our “Digging and Installing Footings” guide.

Composite decking boards

Composite decking boards have been around for quite a number of years. It has been in the last few years that the composite decking boards and products have really started to attract the attention of builders and home owners alike. When composite materials where first released, they where expensive and really didn’t have the true test of time. As time has gone by, timber prices have sky rocketed, and composite products and their technology has improved along with their popularity, making them a very competitive alternative to traditional decking boards.

The biggest advantage of the composite decking boards is their long, low to no maintenance free life. Unlike traditional timber where you need to keep the sealer and vanish in good order to prevent root, you also having inspect regularly for termites and other inspects eating your deck. Please remember that if you are using timber sub floor framing (posts, bearers & joists etc) that you still need to maintain good termite protection practices and regular inspections as the sub floor framing will deteriorate over time.

In the last few years, many composite decking board manufactures have started to play with the colours of their products to give a more natural look. This has resulted in some magnificent looking decks, privacy screens and even decorative fencing.

When installing these prodcuts it is best to follow the installation guides, at the end of the day, the manufacture is the who over time as developed the best way to install their product. There is one tip that I highly recommend keeping in mind when installing composite decking boards, which some manufactures do not mention in their manuals. When laying the boards, do not change the direction of the boards (end for end the boards) as they will look different in colour due to the way the boards a manufactured.

For those that like the technical stuff the boards are predominately made from reconstituted timber and recycled plastics. The percentage of the mix, and the type of plastic used vary from brand to brand. There are many overseas brands coming to Australia, some of these brands haven’t been tested in Australian conditions and may preform poorly. Also keep in mind that if you live in a bush fire prone area you are required by law to use products that meet the building codes bush fire performance requirements which all suppliers of composite decking boards will be able to help you with.

Deck footings: How deep to dig deck footings?

deck footings, deck footing sizes
How big do you make deck footings?

Warning about your deck footings: You MUST, and I mean MUST engage a structural engineer or licensed builder to get the exact size for your deck footings. All ground conditions vary and as such the National Construction Code of Australia (formerly the Building Code of Australia) outlines the different types of soils and the performance requirements for each type of soil conditions. As you can imagine, the performance requirements exist to keep you, your family and friends safe.
So many factors come into designing the size of deck footings that there will never be one size fits all deck footing applications. For example, the size of the deck plus whether it has a roof will change the depth of the footing.
Also, the soil type will alter the width of the deck footing. For example, say a deck footing is required to be 450mm diameter in stiff soil the footing will likely be increased to 600mm in diameter with soft soils.

How deep to dig deck footings?

When digging footings, dig down until solid ground is reached (solid ground is the term used to describe where the ground changes consistencies from soft to hard). Solid ground does not necessarily mean digging until you reach rock, however, at times you may reach rock. When solid ground is reached, it is recommended to dig an additional 50mm into the solid ground. Regardless of reaching solid ground before a minimum depth of 600mm, the deck footing should be at 600mm deep (always dig bigger, never smaller). If your engineer has specified a minimum depth, you need to dig to that depth. If you reach rock (when I say “rock” I mean a layer of bedrock as described in the National Construction Code, rather than stones as defined in the Webster Dictionary) you need to call the engineer for direction.

deck footings, deck footing, deck foundation
Deck footings need to be dug a minimum of 50mm into solid ground.

How wide to dig deck footings?

The best rule of thumb (remembering that an engineer must design your footings) is to have a minimum of 100mm of concrete around your post. If using metal stirrups for timber posts, allow 100mm from the outside of the post, not the stirrup. Metal stirrups keep timber posts out of the concrete footing helping to prevent the timber posts rotting.  The stirrups when installed correctly create a 75mm visual termite barrier.

Tip: When digging deck footings, I always allow a minimum width of 400mm. Two reasons; first, it’s easier to dig; second, the wider deck footing provides enough room for me to move the post around in the deck footing while maintaining the minimum 100mm clearance around the deck post.

deck footings, deck foundations, deck posts
Where to position posts in deck footings.

FYI: It is best to keep the bottom of all deck footings to the same soil type. For example, if one footing is into rock, you should take all footings down to rock. The reasoning, as the ground moves, the different soil types react differently and push deck footings around differently. This movement will result in your deck being pushed out of shape.

Looking for more information about deck footings?  Click here.

Related article: Measuring and taking photos of your footings

How to calculate decking board quantities

Calculate decking board quantities
Calculating decking board quantities is relatively straight forward.

1- Calculate the amount of decking board rows

To calculate decking board quantities required to build a deck is relatively simply process. It is best to start by working out how many rows of decking boards are needed. To do this, measure the width of the deck ensuring you allow for the fascia board and the decking overhang (a detailed outline can be found in the “Installing decking boards” guide). Then divide the width of the deck by the width of your decking boards plus the gap between the decking boards, which is recommended to be 3-4mm. Your calculation should look like this:

“Overall width of the deck in millimetres” / “decking board width in millimetres + spacing between decking boards in millimetres” = the number of rows of decking boards required. (It is always best to round up the answer to the next whole number.)

Example: If the deck is 3 metres wide and 5 metres long (including fascia board and decking board overhang) and the decking boards are 90mm wide and using a 4mm spacing between decking boards, your calculation would be:

3000/(90+4) = 3000/94 = 31.9149 which you would round up to 32.

This deck will require 32 rows of decking boards.

2- Calculate the total decking board lineal meters

Next, we need to work out the total lineal metres of decking required.

Multiply the “number of rows” by the length of the deck – again ensuring to allow for the fascia and the overhangs on both sides of the deck. I suggest and recommend allowing 10% for waste. The final calculation is as follows:

“Number of decking board rows” x “length of the deck in metres” x “1.1″ (multiplying by 1.1 automatically adds on the 10% waste) = total lineal metres.

Using the previous example your calculation would be:

32 x 5 x 1.1 = 176 lineal metres.

Now we have the figure for the total lineal metres of decking boards we need to order.

For more detailed information on how to calculate decking board quantities and how to install your decking boards correctly; you can purchase your own copy of our “Installing decking boards” guide or you may like to visit the “Resource Shop

What to do with your old step treads?

old step treads, recycling old step treads, step treads into coffee table

You finished pulling down your old timber stairs, now you could throw away the old timber step treads, or you could try something a little different.
What I am talking about is you could turn your old steps treads into a coffee table, which will be the envy of all your friends.  I am not going to lie, this will take some effort especially if your old step treads that are really weathered like the ones in the first photo.

Here’s how to build your new coffee table, start by giving your old treads a good sanding on four sides. Now glue your step treads together side by side using small joining dowels (these are available from all hardware stores including the drill bits and mark gauges) and clamp tight. Next you will need to sand the top until you reach your desired finish, if you like all the rustic look you won’t need to sand as much as someone that wants a smoother finish. Now cut the ends of your table top, either to the size you would like or so the ends are nice and straight.

After the top is made, you will need to make your legs and surrounds (the surrounds are the sides that connect the legs together under the table top). To make the legs simply use the offcuts from the posts and for the surrounds use the off cuts from old floor joists. Turn the table top over and mark where you want the legs and cut the surrounds to sit in between the legs. To fix the legs to the table top you will need to glue and dowel the legs to the surrounds (this may get a little messy) and then screw the surrounds to the underside of the table top with the legs attached.

coffee table, step treads into coffee table

Time to sand your new coffee table one last time and coat with some vanish, stain, bees wax or whatever you would like. I do need to warn you before you embark on this endeavour, you friends will want you to make one for them, so best not to tell them if you have any leftover step treads.