There are a couple of considerations that you need for a deck that is going to have a Hot Tub sitting on it. Firstly, what type of wood are you going to make it out of and secondly, is it going to be strong enough to take the weight of a filled hot tub. Let’s start with the weight.
Calculating the weight of a filled hot tub is pretty straight forward. If you can’t find it in the spec sheet or the manual, find the water capacity for example, 1500 litres and then multiply that buy 1kg. 1500 x 1kg = 1500 KG or 1.5 metric tonnes. It’s quite a lot; these Tubs are heavy when filled! What you don’t want is your deck to start to sink or indeed subside in one area. If you tub is not level on the deck, this can cause problems later on.
Therefore, your deck is going to have to be a lot stronger than it would be normally. Firstly, I would suggest seating all of your posts in concrete, at least a couple of feet deep. Just like you would for a 8′ high fence post.
This is a deck that I built in my garden. It was never designed to take a Hot Tub on top but it is super strong with the sunken fence post footers and the cross members are doubled up too. I know it is strong as I build a BBQ on one side of it this year with poured in concrete tops. Probably weighs a good 300 KG but didn’t budge an inch!
Each of the posts were set into post crete. With hindsight, If I had placed the cross members on top of the posts, it would have been even stronger as the weight would have been pressing down onto the posts, rather than the screws holding it in on each side.
Anyway, the point here is that strength is key. Also, the “off the shelf’ deck kits that you can buy are probably not going to cut it. You are going to need something custom for the strength.
What Materials for the Hot Tub Deck.
I think my main point here would be to go for wood rather than composite. I think wood is much stronger and looks so much better. There is also very little difference in cost.
My second point is really a decision on budget. Hard Woods or Soft Woods. You need to be a little bit careful here as some of the decorative hard woods are not particularly strong. My favourite, western red cedar (which I actually made my deck out of but it is not “hot tub weight bearing”) is very light and not very strong at all. Beautiful to look at, but has no real strength. I am sure with the right amount of supports you could make it work, but I would be thinking twice.
The thicker soft woods like pine which is what most of the cheaper decking panels are made from work just fine. They are extremely strong with they have close cross member centres and are screwed into each one. This makes for a good choice if you are going to be sitting your Hot Tub onto a deck.
What about the Finish of your Hot Tub Deck?
Even if your wood is pressure treated with the blue “tanilith-E” chemical that makes it more durable, you are still going to want to stain your deck. I say stain on purpose as I would stay away from anything that is “decking paint”. If it is paint, over time, it is going to flake off and look awful. Spend a little bit more and go with oils or stains. These seep into the wood, bring out the natural beauty of the wood and the grain and most importantly, they don’t flake.
However, you do need to check whether the particular stain is good for horizontal surfaces that are going to have standing water on. Rain and of course the water from your Hot Tub. On my deck, I have a UV protection oil on the vertical deck fence, but I had to use a different oil on the surface of the deck as the UV oil was not suitable, basically doesn’t like having water sit on it. Just read the label first.
The above picture is a before and after when I was staining the deck back in March. This deck has been down 18 months and still looks as good as it did when it was first installed. Maintenance, keeping it clean and oiling it once a year is a must. It will last for ages!
Hot Tub Sunken Into a Deck
The holy grail of hot tub decks? Perhaps? It is certainly my favourite and it was the one that I opted for when I built my own hot tub. There are some considerations that you need to be thinking about. Firstly, is access. My tub was custom build so it was designed to be in ground and the “control room” as I call it is separate and accessible from the top deck through an access hatch.
If you are planning on dropping a hard shell or even an inflatable hot tub into a deck, you need to think about access to the filter and spa pack for maintenance. The last thing you need is having to rip up your deck because you can’t open the door enough to get to the filter to change it. Have a good think and take proper measurements before you drop your Hot Tub in.
You have to admit though, sunken hot tubs just look the part. The are easy to get in and out of and my main aim in doing so was to not be on display to the neighbours when I am in the tub.