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Key takeaways
- Gravel with a base frame suits most hobby kits. It's cheaper, drains freely and can be changed later.
- Concrete suits heavy glass houses, large walk-ins, windy sites and anyone who wants a clean, level floor for carts.
- Concrete anchors best, but it's permanent, more expensive, and more likely to need a permit.
- Both need good site drainage and a level, square perimeter.
- You can combine them: concrete footings or a perimeter with a gravel floor gives you strong anchoring and good drainage.
Quick verdict
Choose gravel for most hobby greenhouses on reasonably drained ground, for renters, and for anyone who wants a cheaper, easier, reversible base. Pair it with a timber or steel base frame and ground anchors.
Choose concrete for heavy glass houses, large or permanent structures, very windy sites, and greenhouses that double as workshops or need a smooth floor.
This comparison is about the base the greenhouse sits on. For interior floor surfaces such as pavers, mats and weed fabric, see best greenhouse flooring. For the full range of options, including piers and pavers, read the greenhouse foundation guide.
Side-by-side comparison
| Factor | Gravel base | Concrete base |
|---|---|---|
| Drainage | Excellent. Water passes through | Poor unless sloped or drained |
| Anchoring | Ground anchors through gravel | Concrete anchors. Strongest option |
| Level and flat floor | Good if compacted well | Excellent |
| Frost behavior | Moves as one unit if well drained | Can crack or heave without proper footing |
| Heat | Little thermal mass | Stores some heat by day, releases at night |
| Cleaning | Harder to sweep. Can be raked | Easy to sweep and hose |
| Permanence | Removable | Permanent |
| Permit likelihood | Lower | Higher (varies by jurisdiction) |
| DIY difficulty | Moderate (heavy work) | Hard. Often a contractor job |
| Price tier | $ | $$$–$$$$ |
Drainage
Drainage is gravel's strongest point. Water passes through crushed stone and away, so spills and irrigation runoff disappear, humidity stays lower, and the base frame doesn't sit wet. That's a real advantage in a greenhouse, where you're watering every day.
Concrete doesn't drain. A slab needs a slight slope toward a drain or doorway, or a built-in floor drain, or you'll have puddles after every watering. Plan that before the pour. Both types still need good site drainage around the outside. Roof runoff can undermine either. See greenhouse gutter and rainwater kits.
Anchoring and wind
Concrete wins here. Anchor bolts into a slab or footing give the strongest hold of any base, which matters on exposed sites. Gravel relies on ground anchors driven through the stone into firm soil below. Those work well in most soils, but holding power depends on what's underneath.
On windy sites, a common compromise is concrete footings or piers at the corners and along the sides with a gravel floor in between. Read how to anchor a greenhouse against wind and best storm anchors and bracing.
Heat and thermal mass
A concrete slab absorbs some heat on sunny days and releases it at night, which can smooth out temperature swings a little. It also conducts cold from the ground if it isn't insulated beneath. Gravel has little useful thermal mass, but it lets you keep soil beds in contact with the ground, and the ground itself stores heat.
Neither base is a heating strategy on its own. If you want thermal mass, water barrels or a climate battery do more. See best thermal mass options and climate batteries and GAHT.
Frost and movement
In freezing climates, water in the ground expands and lifts whatever is on top. A well-drained gravel pad with a rigid base frame tends to move as a unit and settle back, which suits light kits. A thin slab without proper footings can crack or tilt. Permanent concrete bases in frost areas are usually designed with footings below the local frost depth. Ask your building department about local requirements rather than relying on a general figure.
Cost and effort
Gravel is the lower-cost option. The work is mostly digging out sod and topsoil, spreading crushed stone in layers, and compacting each layer with a plate compactor or hand tamper. It's heavy, but most people can do it over a weekend or two.
Concrete costs more in materials and usually in labor. Forms, reinforcement, a pour and finishing are skilled work, and many owners hire a contractor. You'll also need to plan any conduit, drains and water lines before the pour. See how to run electricity to a greenhouse safely, and have a licensed electrician handle the wiring.
Permanence and permits
Gravel can be raked out and reused. Concrete is there for good. That matters if you rent, might move the greenhouse, or might sell a house to buyers who don't want one.
Permanent foundations are more likely to need a permit, but rules vary widely by jurisdiction. Check with your local building department before you buy materials, and get HOA approval in writing if you have one. See can you build a greenhouse in an HOA.
Keep the practical details general
The right gravel depth, stone type, slab thickness and reinforcement depend on your soil, frost conditions, greenhouse weight and local code. Your greenhouse manual may specify requirements, and a local contractor or your building department can tell you what works in your area. The principles hold everywhere: remove organic topsoil, use compactable crushed stone rather than round pea gravel, compact in layers, and keep water moving away from the base.
Choose gravel if…
- You have a light or mid-size hobby kit.
- The site drains reasonably well.
- You rent, or might move the greenhouse later.
- You want to do the work yourself on a modest budget.
- You want in-ground beds or a floor that drains spills.
Choose concrete if…
- You're building a heavy glass greenhouse or a large, permanent walk-in.
- The site is very exposed to wind.
- You want a smooth, clean floor for carts, benches or wheelchair access.
- The greenhouse will double as a potting shed or workshop.
- You're willing to plan drainage, utilities and permits up front.
The hybrid option
You don't have to pick one. Many growers use concrete footings or a concrete perimeter for anchoring, with a gravel floor inside for drainage and in-ground beds. Others lay pavers on a gravel bed for a hard floor that still drains at the joints. For most hobby greenhouses, gravel with a good base frame and anchors is enough. Save concrete for when weight, wind or permanence really call for it.
Frequently asked questions
Is gravel or concrete better for a greenhouse base?
Gravel is better for drainage, cost and flexibility, and suits most hobby kits. Concrete is better for anchoring, cleaning and permanence, and suits heavy glass houses, large walk-ins and windy sites.
Can you put a greenhouse on gravel?
Yes. A compacted crushed-stone pad with a timber or steel base frame and ground anchors is one of the most common greenhouse bases. Use angular crushed stone, not round pea gravel.
Does a greenhouse on concrete need a drain?
It needs a way for water to leave. Slope the slab toward a door or drain, or install a floor drain before pouring. Otherwise, every watering leaves puddles.
Do I need a permit for a concrete greenhouse base?
It depends on your jurisdiction. Permanent foundations are more likely to need a permit than gravel pads. Check with your local building department before you start.
Does a concrete floor keep a greenhouse warmer?
A slab stores some daytime heat and releases it at night, which can smooth temperature swings slightly. It can also conduct cold from the ground. It's not a substitute for insulation or heating.
Can I combine concrete and gravel?
Yes. Concrete footings or a perimeter give strong anchoring, and a gravel floor inside drains well and allows in-ground beds. It's a common compromise.