This is the question that should get asked before the model is chosen, and it usually gets asked after the deposit. So here is the whole thing, with the arithmetic in the open.
The short version: a typical residential deck in Canada is designed for a live load of about 40 to 50 lbs per square foot. A filled hot tub with people in it runs between roughly 88 and 108 lbs per square foot. That is not a small margin, it is roughly double, and it is why "my deck feels solid" is not an answer.
How to Work Out Your Own Number
Three inputs, all of which you can get off a spec sheet:
- Water. Volume in gallons multiplied by 8.34 lbs. Water is the dominant term and it is the one people leave out.
- The spa itself. Dry weight, which is the number the brochure leads with.
- People. Roughly 180 lbs each, at the seat count you will actually use.
Add all three, divide by the footprint in square feet. That is your load. Note that displacement means a person in the water does not add their full weight to the total, but sizing on the conservative figure is the right instinct for a structure you are trusting with your family.
Every Eco Spa Model, Calculated
We publish this on every model page because no one else in the category does. Loaded means filled and carrying its rated occupancy.
| Model | Footprint | Filled | Filled + people | Lbs / sq ft |
|---|---|---|---|---|
| E1 | 72" x 60" | 2,128 lbs | 2,848 lbs | 95 |
| E2 | 76" x 46" | 2,018 lbs | 2,378 lbs | 98 |
| E3 | 77" x 60" | 2,388 lbs | 2,928 lbs | 91 |
| E4 | 77" x 60" | 2,388 lbs | 3,108 lbs | 97 |
| E5 | 77" x 60" | 2,477 lbs | 2,837 lbs | 88 |
| E5 Deluxe | 77" x 60" | 2,477 lbs | 2,837 lbs | 88 |
| E6 | 78" x 78" | 3,292 lbs | 4,552 lbs | 108 |
| E6 Deluxe | 78" x 78" | 3,292 lbs | 4,552 lbs | 108 |
The pattern worth noticing: the lightest total load is not the lightest per square foot. The E2 holds the least water of anything we build but concentrates it on the smallest footprint, so it reads higher per square foot than the E5. Structure cares about the concentrated figure, not the total.
What a Deck Actually Needs
If the number comes back over what your deck was designed for, and it usually will, the fix is not normally to rebuild the deck. It is to carry the spa independently of it:
- Footings directly under the spa footprint, sized by an engineer, with posts and beams that take the load to ground rather than through the existing joists.
- Doubled or sistered joists under the load area on a shallower deck.
- Ground-level placement beside the deck, which is the option people dismiss too quickly. A spa on pavers next to a deck costs nothing structural and looks the same once it is in.
Whatever you do, get it in writing from someone qualified. A deck failure under a filled spa is not a repair, and it happens with people in it.
Rot, Which Is the Other Half of the Question
Load is the calculation everyone runs. Age is the one they skip. A deck built in 2004 was designed for 2004's loads and has had twenty BC winters since. Before anyone works out psf, check the posts at grade, the ledger board where the deck meets the house, and the joist hangers for corrosion. A structurally adequate deck with a rotted ledger is more dangerous than an undersized one in good condition.
Or Skip It Entirely
The reason this question comes up so much is that most hot tubs require a poured concrete pad or a purpose-rated deck, because their load concentrates on a wood frame. An Eco Spa distributes across a one-piece base, so it sits on compacted gravel, pavers or an existing patio as delivered. No pad, no cure time, no contractor, and none of the arithmetic above.
If a deck is the only place it can go, tell us the model you are considering and we will give you the loaded figure to hand to your engineer. See what surfaces work, or ask us.
Frequently Asked Questions
Can you put a hot tub on a deck?
Sometimes, and the answer is arithmetic rather than opinion. Residential decks in Canada are typically designed for a 40 to 50 lb per square foot live load. A filled hot tub with people in it runs between roughly 88 and 108 lbs per square foot depending on the model, so most decks need either a structural review or reinforcement before a spa goes on them.
How much does a hot tub weigh when full?
Take the water volume in gallons, multiply by 8.34 lbs, and add the dry weight, then add about 180 lbs per person who will be in it. A 230 gallon spa weighing 470 lbs dry comes to about 2,388 lbs filled and 2,928 lbs with three adults in it. Dry weight on a brochure badly understates the real load.
Do I need to reinforce my deck for a hot tub?
Unless the deck was specifically built to carry one, assume yes until an engineer or a competent builder tells you otherwise. Reinforcement usually means additional footings and beams directly under the spa footprint rather than rebuilding the deck. Get the opinion before you order, not after.
Is it cheaper to put a hot tub on the ground?
Almost always, and it is also faster. On grade an Eco Spa sits on compacted gravel, pavers or an existing patio with no concrete pad, no contractor and no cure time. That removes the entire structural question along with the cost of answering it.