Why We Build Outdoor Saunas on Concrete Footings

A sauna is a building. We believe its foundation should be treated like one.

A finished outdoor sauna may look simple.

But underneath the cedar, there is a real building carrying real weight.

Framing. Roofing. Siding. Insulation. Interior cladding. Benches. Glass. A heater filled with stone. Four, five, or six people at a time. Maybe an attached porch or cold plunge.

It adds up quickly.

And every pound eventually ends up in one place: The foundation.

That's why at Woodinville Sauna, the foundation isn't an afterthought. We build our outdoor saunas on concrete footings designed to give the structure stable, intentional bearing points and keep the building elevated above the wet Pacific Northwest ground.

We're not trying to find the easiest place to set down a sauna.

We're building something we expect to stay there.

A sauna carries more weight than you might think

Start with the building itself.

Floor decking, wall framing, roof structure, metal roofing, exterior siding, insulation,v interior wood, benches, doors, windows and everything else required to turn an empty structure into a finished sauna.

Then add the heater.

Depending on the heater, the mass of stone alone can be substantial. All of that weight may be concentrated into a relatively small area of the floor.

Then people walk in.

A sauna designed for six adults needs to support six adults—not just when it's new, but over thousands of heating and cooling cycles for years to come.

If the design includes a porch, cooling area or cold plunge, the loads can become even greater.

A 100-gallon cold plunge contains more than 830 pounds of water before adding the weight of the tub or the person sitting in it.

These aren't reasons to overbuild everything.

They're reasons to think about what's supporting it.

A solid foundation makes the sauna feel… solid

A sauna should feel stable the moment you step inside.

When sauna goers walk through the door, shift their weight, or climbs onto the upper bench, the building shouldn't sway beneath them. And when someone steps down or jumps off the high bench, the floor should feel firm.

Concrete footings help create that solid, grounded feel.

By giving the structure defined bearing points and a properly supported floor system, we reduce the movement that can occur when people enter, sit, stand or move around inside the sauna. The building feels connected to the ground instead of reacting to every change in weight.

That matters for comfort, but it also matters for the long-term performance of the structure.

Why not just put it on gravel?

A properly prepared gravel pad can provide a stable, well-draining base, and plenty of outdoor structures are successfully built on them.

Our approach is different.

Rather than supporting the sauna near the surface across a pad, concrete footings give us dedicated structural bearing points to build from.

We can establish the elevation of the building, level our floor system, locate structural loads and know where those loads are being transferred into the ground.

For a sauna we're designing as a permanent part of someone's property, we prefer having that foundation beneath us.

Get the wood off the ground

Then there's something every Pacific Northwest homeowner understands: Water.

Western Washington spends a significant part of the year wet.

Rain falls. Water moves across a property. Soil becomes saturated. Vegetation grows. Organic material collects.

Wood structures generally benefit from separation from that environment.

Concrete footings allow us to elevate the sauna's floor system above the ground rather than placing the building immediately over a large surface pad.

That creates space underneath the structure.

Water can drain.

Air can move.

The floor structure stays separated from the wet ground below.

And drainage can be considered as part of the site rather than as an afterthought.

A foundation is built for what happens over time

Most freshly installed saunas look great.

We're more interested in year ten.

Over time, ground gets wet and dries. Soil settles. Water finds paths through a property. Seasons change.

Small movements underneath a building can eventually become noticeable above it.

A door begins rubbing.

A deck moves slightly out of level.

Finish materials shift.

The foundation is one of those parts of a project that you may never think about again if it's done well.

That's exactly the point.

We're not building something we expect you to replace

This is ultimately why we care so much about something you'll barely see when the sauna is finished.

We don't think of a custom sauna as another backyard product.

It's not something we're designing to be dropped onto the property, used for a few years and eventually replaced.

We think a sauna should become part of the property.

It should respond to the landscape around it. It should weather and age naturally. It should be used through thousands of hot-and-cold cycles.

Ideally, it should still be there long after you've stopped thinking about what it's sitting on.

That changes the way we approach the foundation.

Build from the ground up

Not every outdoor sauna in the world needs to sit on the exact same foundation. Site conditions, building size, loads and local requirements all matter.

But for the custom outdoor saunas we build, we start with concrete footings.

They give us intentional structural bearing points. They elevate the wood structure away from wet ground. They create space for drainage and airflow beneath the building. They help keep the sauna from moving or swaying when people walk in, move around or step down from the high bench. And they give us a solid foundation for everything we're going to build above it.

Insulation matters.

Ventilation matters.

Bench height matters.

Heat matters.

But before any of those things can do their job, the building needs somewhere to stand.

We build our saunas like homes. We start with the foundation.