Hot Tub on a Deck

What a filled hot tub weighs

A hot tub is mostly water, and water is heavy. These are the makers' own published figures for common sizes, read on 2026-11-02:

Those weights are before anyone gets in. Six adults add several hundred kilograms more, all inside the same square.

Source: Arctic Spas: Whistler specifications · Arctic Spas: Eagle specifications · Beachcomber: all models specifications · Jacuzzi Canada: J-335 · Arctic Spas: McKinley specifications

Can a normal deck hold a hot tub?

Usually not without changes underneath it. The Eagle above, spread over its own 50 square feet, puts about 67 pounds on every square foot before anyone climbs in. A standard house deck is designed for less than that.

The Town of Carleton Place's 2025 deck guideline, written to the 2024 Ontario Building Code, uses the standard residential live load of 1.9 kPa, or 39.7 pounds per square foot. It says plainly that decks supporting hot tubs are not covered by it.

What the hot tub makers ask for

The manufacturers set the bar higher still, and they do not agree on the number:

• Arctic Spas' owner's manual: a deck that can support 146 pounds per square foot (7 kPa). Its spec pages say 100.
• Hydropool's 2025 owner's manual: a properly built deck that can carry 250 pounds per square foot (1,220 kg per square metre).
• Both: know the deck's rated capacity before the tub arrives, and ask a qualified contractor or structural engineer.

Hydropool adds two rules worth knowing. The tub's cabinet is decorative, never support, so the tub must never hang from the deck or the cabinet. And the deck has to leave room to reach the tub on every side for repairs.

Source: Town of Carleton Place: Part 9 decks guideline, OBC 2024 edition (PDF) · Arctic Spas owner's manual (PDF) · Hydropool 2025 Signature owner's manual (PDF)

How to build a deck that can hold a hot tub

The load goes down through the framing to the footings, so that is where a hot tub deck is different. The boards carry the people; the frame and the footings carry the tub.

• Joists: Trex's 2026 installation guide says to plan joist spans ahead, "especially important if installing a hot tub", and to ask a local building engineer or inspector for span recommendations under heavy items.
• Footings: below the frost line. On clay, or soil nobody has identified, the Code sets at least 1.2 metres below grade. Hydropool recommends footings below the frost line where freeze and thaw can move the ground.
• Access: Arctic Spas asks for at least 24 inches (600 mm) of clear space around the tub for service.

As a deck builder in Ottawa, we design the deck in 3D and AutoCAD first, so the tub, its footprint and the framing under it are on the drawing before anything is built. Our guide to frost depth for deck footings in Ottawa explains the 1.2 metre rule.

Can you put a hot tub on a composite deck?

Yes, if the frame under it is built for the load. TimberTech's own FAQ answers that question with a yes, and says the joist system, not the boards, is what carries the weight. It also caps joist spacing at 16 inches on centre for residential decks.

Trex says its decking cannot be used for structural applications. In other words, composite boards are a surface. Our composite decks page covers the boards we install from Trex, TimberTech and Fiberon.

Source: Trex 2026 installation guide, page 8 · Trex 2026 installation guide, page 22 · TimberTech FAQ

Do you need a permit for a hot tub on a deck in Ottawa?

Probably two, and sometimes three. The deck, the enclosure and the wiring are separate questions.

The deck

The City of Ottawa requires a building permit for a deck attached to or beside the house once its walking surface is more than 600 mm (24 in.) above the ground, whatever its size. A freestanding deck needs one when it is both over 10 square metres and over 600 mm high. Our Ottawa deck permit guide has the full wording.

A deck under 600 mm needs no permit, but the City says exempt projects must still meet the Building Code. The hot tub's weight does not stop counting because nobody inspects it.

The enclosure: Ottawa's Pool Enclosure By-law

Ottawa's Pool Enclosure By-law (2013-39) treats a hot tub that can hold 600 mm of water as a pool. It needs a fence and gate like a pool, unless it has a safety cover that meets the by-law:

• able to hold a 90 kg load, or compliant with ASTM F1346;
• permanently attached to the hot tub or its supporting structure;
• fastened and locked whenever the tub is not in use.

A locking cover saves the fence. It does not save the permit. The City's FAQ says you must still get a Pool Enclosure Permit, with an inspection, even when the lid locks, and you must provide the cover maker's specifications with the application.

If you would rather fence it, our pool fences page covers the iron and aluminium enclosures we build.

The wiring: an ESA permit

The Electrical Safety Authority says pool and hot tub installations usually need both a building permit and an electrical permit, and that the electrical one is often overlooked. The person doing the electrical work files the notification of work with ESA; a Licensed Electrical Contractor files it for you.

ESA's 2025 bulletin on pools and hot tubs adds three rules that shape where the tub sits:

• no receptacle closer than 1.5 m to the tub;
• equipment within 3 m of the tub GFCI-protected, unless a permanent barrier separates it;
• the tub's controls behind a barrier or at least 1 m away, unless they are built into the factory unit.

The makers add their own. Arctic Spas asks for the disconnect to be visible from the tub and at least 1.5 m (5 feet) from the water, and Hydropool asks for a dedicated circuit on a two-pole Class A GFCI.

Source: City of Ottawa: decks · City of Ottawa: projects not requiring a building permit · City of Ottawa: Pool Enclosure By-law 2013-39 (PDF) · City of Ottawa: pool enclosure FAQ · City of Ottawa: pool enclosures, pool, hot tub, pond · ESA: Toolbox Talks, May 2025 (PDF) · ESA: how do I notify ESA about electrical work · ESA Bulletin 68-7-16, May 2025 (PDF)

Where not to put a hot tub on a deck

The deck is not always the best place for the tub. Three spots cause most of the trouble:

• On an existing deck nobody has checked. You cannot see the joists or footings from the top, and the makers say to know the rated capacity first.
• On the cantilevered edge. The overhang past the beam is the weakest part of a deck, so a heavy load belongs over posts and footings.
• Hard against the house wall. Both makers want access on every side for service.

The alternative is a pad at ground level with the deck built around it. A ground-level interlock patio carries the tub on a stone base instead of a frame. Our guide to deck vs. patio in Ottawa compares the two.

Running a hot tub on a deck through an Ottawa winter

Most Ottawa owners keep the tub running all winter, and the makers build for that. Hydropool's manual describes a winter mode that runs the pump when the water in the heater reaches 4 °C, to stop it freezing.

If a tub will sit unused in deep cold, both makers say to winterize it properly. Arctic Spas says improper winterizing can void its warranty and that damage from ice in the spa is excluded. On the deck side, clear snow off the cover and the boards around it, so the weight you are carrying is the weight the deck was built for.