Polymer Deck
One of the most common things people like to work on is building a deck or a patio at this time of year. Towards the end of May usually the frost comes out of the ground in the Ottawa area and that’s when things begin to happen.
Whether you are building a new deck or replacing an old one, the right process needs to be thought about before beginning. The first thing of course is to have a plan and to think it out to determine how you will be using the deck. Will you barbecue on it or are you looking for a shady place or a sunny place? This will determine what side of the house you build it on.
For example, our deck on our house is built on the north side of the house and what’s nice about that is that we get sun in the morning and as the sun rises in the sky we get a partal shade from our house behind us and as it comes down on the west we get t he sun in the afternoon.
Now we are not going to get into building gazebos or putting a roof on the deck. We want to stick with the basic structure for now. So the most important thing after you have your plan is to determine whether it is a floating deck, or is it going to be one built on piers down below frost level. There are two different things you have to think about here. Building a deck on floating or deck blocks will require that this structure will have to be separate from the house. It will have to stand alone, so that it can move up and down with the different movements of the soil from summer to winter. The house is typically built below frost unless it’s made with a slab construction, so you can have a minimum ¼” spacing but cannot connect to it.
Wood Decks
If you are going to have a floating deck, deck blocks are a good option. If you are going with deck blocks make sure that you dig down below 10” to 12” below each deck block in an area slightly larger size than the size of the deck block and install gravel and or stone dust and pack it before you put that deck block on. Usually the deck block has a spot in the middle where you can insert a pressure treated post and it fits right in the square part. There is a new option on the market now too that you can take these adjusting brackets that you can install in the deck block and then put your 4”x4” post right in the adjusting bracket . This is so that if you have movement or a little bit of settlement, you can adjust the deck . If you have an access door to get under your deck, you can turn these brackets. They are almost like an adjusting telepost where you can thread them up or down to adjust the height of your deck.
The other way to do it (which is the way I built my deck) is to build it below frost. In this case you would build it on piers and you want to be at least 5-6’ down in to the ground because the frost does drop quite a ways and you don’t want it to be heaving those posts. When you put these posts in , some people use a special pressure treated post that goes down on to a concrete foot down in the ground. Make sure you have the treated end down and treat the sides of the post with foundation coating as well up to grade level. The other way to do it is with concrete in a concrete pier which goes straight down, coming in different sizes such as 8”,10” or 12” diameter. I like to go with the minimum 10” diameter and on the bottom I like to go with a footing that kind of goes out and becomes part of the concrete pier. When the concrete is poured, it’s like a big foot on the bottom. This way the frost can never heave that post up because it is held down by the “foot” of the concrete at the bottom way down below grade. Make sure when you dig the holes that you do not have loose soil at the bottom and that you are on a solid bed. Once you have those piers poured and you back fill them, make sure they are at least 8” out of the ground. If not your posts and or beams could rot because they are too close to grade. Next step is to set your posts and beams on. The size and spacing of your beam work will be determined by your plan and the building code. I like to use a 2” x 10” built up beam, either a 2ply or 3ply depending on the distance between and over top of that I would go over it with either 2” x 6”, 2” x 8”or 2”x 10” joists depending on the span above. I like to stick with a 16”on centre spacing for the joisting. You can go with a wider spacing up to a 24”, but then there is a little bit of spring in the deck boards. I am a fan of using something other than pressure treated to finish the deck, but many decks are built with it . I like to use cedar with whatever you see. There are many types of deck boards you can go with now that don’t need any painting or maintenance. They are more expensive than wood although cedar is a step up from pressure treated. So what to go with? Whether you go with a wood deck on the outside or polymer deck on the outside, both requires a basic wood structure underneath. I always recommend a pressure treated undercarriage and the joisting and beam work to be pressure treated. Make sure when you do your cuts that you treat the ends because when you cut a pressure treated board the inside is still susceptible to rotting if you do not field treat it with end cut preservative. So the difference between wood and polymer is price first of all. Looks and feel are important too. Some polymers have a wood grain. Others are smooth. The thing that you have to think about here in Ottawa is that if you have something smooth, you may get a very slippery surface when the weather gets colder and/or icy. It can be very dangerous in the winter time. So if you go with the wood deck it looks nice but it will require repeated staining’s over a period of time not unless you let it go gray if its cedar. You can do that as well – some people like this look and they don’t want to have to do the maintenance but they still like the look of wood. There are so many brands of manufactured deck boards and most of them are good. Different price ranges doesn’t mean one is better or worse than the other. A lot of it has to do with the esthetics, feel and the look of what you are getting.
There are different systems for attaching the polymer boards, you can go with the surface screw method to fasten it down or you can use hidden fasteners. A lot of people like to use that instead and usually put a space in between to let the water get out. When you are doing the posts on a wood deck, I always like to take the posts that go up for the railing and put them down in to the joisting and brace them back so they are very solid instead of a surface post. In this instance I am talking about wood railings or a vinyl sleeve that goes over a wood post. If you go with an aluminum railing it can be surface mounted and its very solid and that’s how it is designed. You do however, want to make sure that you put proper blocking in underneath to support the aluminum post. For the decking I recommend a 5/4” x 6” radius edge board. That’s a board that has a little bit of a routered edge so that it wears a little better rather than a square edge board although square will work as well. On the outside edge of the deck we like to use a trim board to cover the end cuts whether its polymer or wood.
Also, there are different styles of decks. If you are up off the ground a ways, it’s going to have to have knee bracing underneath to make sure that the deck is properly braced. Some people like to skirt it in. If we skirt in a deck, we like to build a pressure treated skirting wall out of 2”x 4” lumber that is braced back to the underside of the deck. We cover it either with a lattice work or a solid type board with a similar spacing to what is on the deck, either a 5/4” x 6” or 1”x 6”. This works quite well and makes a solid surface. You have to make sure that you leave the bottom of the skirting up 2-3” off the ground so that when the soil heaves in the winter time it won’t grab the edge of your deck on the skirting and heave it up and down between the seasons. This keeps the animals out as well. Some decks are up quite high. Those decks don’t really require skirting. Sometimes light needs to come in through a basement window or if it’s a two storey deck you need light coming in to the one storey windows. So that’s something to think about. The most important thing is to make sure you have proper bracing back to keep that deck solid so that it does not move when you have a bunch of people on it. Always stick to building code standards in any deck design or construction.
So hopefully that gives you some solid deck building advice. Cheers.
Jacob Huyer
Huyvan Home Improvement
ph:613-821-9300
www.huyvan.com
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