You have finally decided to expand your living space by adding a deck, like everything in construction this can either be a good experience or a catastrophe. Decks that work well and are safe, can offer years of good memories with friends drinking and Barbequing, or it can be years of frustration tripping and slivers in the feet. We are going to explore some of the basics that will ensure your deck is a pleasant experience.
In this breakdown we are going to explore two deck styles, the stand-alone deck that is in a back yard not attached to any permanent structure (option 1), and the backyard deck attached to a home (option 2). Both of these decks will be over yard space and allow for drainage right into the ground.
Foundations.
The foundations you can use will vary depending on the option you choose. In both cases a proper concrete pad and post option is going to be the very best option. This style involves digging a hole 36 inches deep and 24 inches in length and width. You then pour a concrete pad, 6 -8 inches deep with rebar laid in a square inside the concrete. Two dowels are pushed vertically into the center of the pad and then a 24-inch tall sonotube is placed down around those dowels and filled with concrete to create a pad and post. A welded metal saddle is then pushed into the top of the tube while the concrete is wet or set in by drilling a hole and using a concrete epoxy, so the saddle is fixed in the concrete to prevent future lift of the deck in a windstorm.
This is always the very best option. But not always necessary. It depends on the ground type and what will be on the deck. If a hot tub was a future plan, then this is the only foundation option that is safe. But if a BBQ and some lawn chairs is the ultimate goal this option may be more than what’s required.
The ground around a deck can be significantly affected by water. The most evident time for this is in the winter and spring. When it gets really cold, frost penetrates the ground, when this happens the freezing water in the ground can cause the ground to raise and lower several inches. In Alberta where the ground is mostly clay, the ground can move 6-8 inches up and down. Here in BC we don’t have the same problem but around a home where the ground has been replaced by soil 1-3 inches can be expected. The method mentioned above will mitigate this issue. It will also prevent sinking of your deck if you put a heavy load on top like a hot tub when the ground is fully saturated by water as often happens in the spring. It’s also the best way to protect your home if the deck is attached to it. As you can imagine a deck going up and down while attached to your home could cause serious damage.
The second option is a concrete post put in the ground without a pad. This is the second-best option, a hole is dug 30 inches deep, a 8 inch sonotube is placed in the hole and concrete poured into the tube. A little extra concrete in the bottom of the hole is never a bad idea, this creates a makeshift pad as the concrete will usually spill out and create a lip making it harder for lift to take place and a little more surface area to prevent sinking. Again, a welded concrete saddle is added to the top to attach the legs for your deck. This option can be used when attaching small decks to a home that will have no serious weight and is also a good option for standalone decks. This is not an adequate option for decks that are attached to the second floor of a home, or decks with a hot tub.
Lastly, the concrete post holder option. This option is ok only for standalone decks not attached to any structures. This style allows for the maximum movement of the deck, to properly install these manufactured post blocks you will still need to dig out ground where you want to put them, remove a minimum of 8 inches of ground in a 24 inch square, fill that hole with gravel or crush. Make sure you tamp it with a mechanical packer. Place the block on top of the gravel as center as you can. Because this method offers no uplift protection you will have to make sure you put in some ground anchors with cables to protect against uplift. A deck sitting just above the ground will act like a giant wing in a windstorm and will want to lift right off the ground.
Structure.
There are 3 material options for structure; treated wood, cedar and fir/. All decks should be built out of these materials, I have seen sealed exterior decks rot from the inside, because of one small leak, a extra few hundred dollars in material would have saved a repair in the thousands of dollars. Treated is the bare minimum for any decks. Treated material is treated with a variety of chemicals to help wood resist rot and water. It is also insect resistant. Because of this it is an acceptable material for the structure of decks. It is also the cheapest option of the three listed above.
A few things to consider when using treated material, you have to use powder coated hangers and coated screws. Treated material is extremely corrosive to metal. Screws that would normally last 100 years will lose all structural strength within a year if placed in treated material. Coatings on screws and hangers will prevent the corrosive aspects of the wood from rusting the metal.
Cedar is a naturally treated material, it is what we are trying to achieve by using chemicals, but we all know nature does it best.
Fir is also a good option as long as there is air movement and the material can dry out. Fir does not last if submerged or permanently wet. However, in the case of a deck where it will have lots of opportunity to dry out regularly fir is a great option. It is stronger than treated spruce and is also naturally bug resistant. It’s also a natural product and if you will see the structure it is much better looking than treated material.
When building the structure of a deck it’s important to follow the BC building code for structural requirements. Something to consider when building a deck is to always double your outside boards. We do this for a couple of reasons. One it prevents bowing and warpage which can pull the deck apart as it dries. It also gives us significantly more meat to lag bolt our railings into. I have seen many railings screwed only into the decking boards. If one too many people decide to lean on the railing those decking boards won’t hold. They simply aren’t designed to hold that kind of weight.
For the legs of the deck 4×4 posts sitting on top of whatever foundation method you chose is adequate. Don’t forget to cross brace your legs, I have watched decks shift and lean, the ground moves or too much weight is added to a side of the deck, without those cross braces where the legs connect to the deck shift and like when one leg of a chair gives out the deck becomes unsafe.
Decking
Decking material is usually the most expensive part of the deck. When you consider that a 20×20 deck is 400 square feet and will require 70 plus boards of material the costs start to add up. There are a lot of options out there, I am only going to talk about the three, manufactured, cedar and treated.
Manufactured boards are the most expensive by far. They usually come in at a minimum of twice the price of the wood products. Please don’t be fooled, not all manufactured products are created equal. Scratch resistance, dent resistance, and UV protection are all important elements to consider when choosing a decking. I have had to replace manufactured decks for clients because they bought a dog and the decking they chose originally could not handle the toenails of a big german shepherd. I have also replaced wood decks with manufactured material because the sun warped the wood to a point that the screws weren’t holding the deck down any longer.
Manufactured is more expensive but it doesn’t need to be coated every 2-5 years. It won’t warp, it’s 100% water resistant, making it the only real option for a hot tub deck. It won’t give you slivers when hanging out with bare feet. It does have a way of heating up more than wood though. So, while the darker colors might be much more attractive it is rarely the best option for a deck. Lighter colored decks will stay cooler and it is no fun having to slip on sandals every time you climb out of the pool.
Cedar is the next most expensive wood option, if wood is your choice then I will always recommend cedar before treatment. Because it is a natural product it is much safer. Slivers from a cedar deck won’t get infected, it’s safe if your dog decides they want to chew on a corner of the deck it isn’t toxic. And decks need to be family safe. The other bonus about cedar is that it is more attractive and is stain ready right from the store. Properly coated with a UV resistant stain and clear coat it can resist sunlight, it’s naturally water resistant so it won’t rot or swell but remember it still needs to be serviced every 2-5 years. Cedar still needs to be installed correctly, making sure you put the grain down so it looks like a rainbow will prevent the edges from raising, creating toe catching lips. Just remember if you look at the end of the board and it looks like a cup you need to flip the board. Wood will always warp. There is no way to prevent this, it is simply an aspect of wood that we cannot mitigate. So keep that in mind when choosing a decking material.
Lastly, I have already mentioned the reasons I don’t prefer treated material for decking. It’s the cheapest option. It’s not a bad option for a back set of stairs. But I don’t suggest it ever for a patio style deck. It is a functional material but that’s about all. It will also need 30-60 days to be ready for coating. Meaning that your contractor will need to return in 1-2 months to finish your deck properly. If it isn’t given this time, the deck will fail. The moisture in the wood will be trapped and warpage will be more significant, and the stain will not dry or seal properly and your deck will need to be serviced again within 6-12 months.
Finally, railings. Any deck with a drop of more than 24 inches requires a railing, often people will attach a planter next to a deck creating a big step that makes the drop less, and this is a really good option. However, if you have kids, I would always recommend a railing. It only takes one person missing a step and falling off the edge to ruin a good thing. There are many options and they will depend on your budget, in order of cost effectiveness – a wood railing, these can be painted or stained. They will require servicing every 2-5 years. Metal spindle railings, these are a beautiful option and come in a variety of color options. Glass railing, this is of course the most expensive option, in recent years a top cap has been required by different districts meaning you don’t get the truly invisible look most people are going for. Diamond rings tapped on the edge of a piece of tempered glass have the nasty habit of shattering the railing. A required top rail has been added as a safety precaution. They may be beautiful, but they do require constant glass cleaning. One thing to note is that if your deck is around a pool that deck is required to have a locking gate, this is for child safety
There are a lot of things to consider when building a deck and like all successful projects your deck will start with good planning. Make sure to look at all the variables and understand the effects that adding a deck will have on any structure you attach your deck to.