How to Anchor a Greenhouse to Concrete: Step-by-Step Guide (2026)

To anchor a greenhouse to concrete, you bolt its base frame or brackets to a level, fully cured slab or strip footing with masonry anchors. Most kits use concrete screws or wedge anchors set in holes drilled with a hammer drill. The steps are simple, but the details matter: the right anchor, a clean hole and the manufacturer's own instructions.

We are a small, woman-owned greenhouse business in Georgia. Anchoring is one of the most common questions our customers ask before delivery day. This guide pulls together what the manufacturers we work with actually say, plus the anchor makers' own install rules.

Why do you need to anchor a greenhouse to concrete?

A greenhouse is light for its size and catches wind like a sail. Without anchors, a strong gust can lift or shift it. That can twist the frame and crack panes.

Anchoring also keeps the frame square. Doors and roof vents only close well when the base stays put. Exaco's Riga manual adds that anchoring "is vital and should be checked periodically."

Each greenhouse is rated for a certain wind and snow load. Those ratings assume it is anchored as the maker directs. For example:

• Cross Country Parkside: rated for wind gusts up to 85 mph and 32 lbs per sq ft of snow as standard, with upgrades to 140 mph and 110 psf.
• Riverstone MONT: rated for 65 mph wind and 24 lbs per sq ft of snow.

Should you use a concrete slab or a strip footing?

You can anchor to either. Each has trade-offs.

Base	What it is	Pros	Watch out for
Strip footing	A narrow concrete band under the walls only	Soil floor inside; good drainage; uses less concrete	Must be level all the way around
Full slab	Concrete under the whole greenhouse	Clean, solid floor; easy to sweep	Needs a slope and a drain inside
Existing patio	A slab you already have	No new pour	Check it is level, solid and uncracked

For the Riga, Exaco suggests an 8-inch-wide strip foundation, poured to the frost line as the manufacturer recommends. If you pour a full slab instead, the Riga manual says it must be "100% level and flat," with a slope and drain inside.

Hoklartherm, the Riga's German maker, recommends a concrete base for large houses and for insulated glass. Our practical guide to a greenhouse foundation compares every base type in detail.

How much concrete do I need for a greenhouse footing?

If you are pouring a new strip footing, this quick formula gives you a good starting estimate.

What anchors should I use to attach a greenhouse to concrete?

Three types cover most backyard greenhouses. Always check your greenhouse manual first, since it may name a specific type and size.

Anchor	How it holds	Drill bit	Embedment	Used by
1/4" concrete screw (Tapcon type)	Threads cut into the concrete	3/16" carbide	1" to 1-3/4"	Riga (Exaco's suggestion)
Wedge anchor	A clip expands as you tighten the nut	Same size as the anchor	From 1" for a 1/4" anchor	Cross Country posts (stainless)
Screw + masonry plug	Plug expands as the screw goes in	Sized to the plug	Per plug maker	Cross Country base, Hoklartherm frames

Bit and embedment figures come from Tapcon's and wedge-anchor makers' published install guides. Always follow the instructions on the box you buy.

Choose stainless steel hardware where you can. A greenhouse is warm and damp, and Exaco recommends stainless for that reason. Plain steel can rust over time.

How each greenhouse brand anchors

• Hoklartherm Riga and Riga XL: the kit includes L brackets for a concrete strip or knee wall. Concrete anchors are not included. Exaco suggests 1/4" concrete screws, 2.5 or 3 inches long.
• Cross Country (BC Greenhouses): the base fastens with a 1-3/4" screw into a masonry plug. Structural posts are fastened with heavy-duty stainless steel wedge anchors.
• Exaco Janssens Royal Victorian: comes with a 4-1/4" high foundation frame. Follow the assembly and foundation document on the product page to fix it down.
• Other models: check the product page's foundation document, or call us and we will look it up for you.

How do you anchor a greenhouse to concrete, step by step?

Here is the method we walk our customers through. Read your greenhouse manual alongside it, since it always comes first.

What you will need

• Hammer drill and carbide-tipped masonry bits of the right size
• Concrete anchors (stainless steel if possible), sized per your manual
• Tape measure, long level and a marker
• Shop vacuum, hand pump or compressed air, and a nylon hole brush
• Hand torque wrench (for wedge anchors) and safety glasses

The steps

1. Check the concrete. Make sure it is fully cured, level and free of cracks where the anchors will go.
2. Set the base frame in place. Square it by measuring both diagonals. They should match.
3. Level it. Check every side with a long level before you mark anything.
4. Mark the holes through the brackets or base frame holes.
5. Drill each hole to the right depth (see the box below). Wedge anchors are usually drilled and set right through the bracket. For other anchors, follow the box on whether to move the frame aside.
6. Clean every hole. Brush, then blow or vacuum out the dust. This step is easy to skip and costs you holding power.
7. Fit the anchors loosely first. Get all of them started before you tighten any.
8. Tighten evenly, working around the frame. Recheck square and level as you go.
9. Seal the base if your manual allows. A bead of sealant along the outside edge stops drafts and water.

How far from the edge of concrete should anchors be?

Anchors set too close to a slab edge can crack the concrete. One wedge-anchor supplier gives a simple rule of thumb:

• Edge distance: at least 5 anchor diameters from any free edge.
• Spacing: at least 10 anchor diameters between two anchors.

For a 1/4" anchor, that means at least 1-1/4 inches from the edge. An 8-inch strip footing gives you plenty of room if you center the base on it. Your anchor maker's data sheet has the exact numbers, so check it.

Can you anchor a greenhouse without concrete?

Yes, for some models. The Riga Foundation Frame is made of anodized aluminum and fits every Riga and Riga XL size. Exaco says it is buried in a trench about 4 to 5 inches deep, with no concrete work.

Hoklartherm says small free-standing houses up to about 15 square meters (about 160 sq ft) don't need concrete. The frame sits in the soil on flat supports at the corners. On long houses, add supports about every 2 meters (6.5 ft) along the long sides.

For a bigger house, a glass house or a windy site, concrete is still the safest choice. See our comparison of gravel, concrete and base kit foundations. Building on a low wall instead? Read our stem wall guide.

What mistakes should you avoid when anchoring a greenhouse?

• Drilling green concrete. Anchors don't hold well in concrete that hasn't cured.
• Skipping hole cleaning. Dust stops the anchor from reaching full depth and cuts its holding power.
• Over-tightening. Too much torque can snap a concrete screw or weaken the anchor. Use a hand torque wrench, not an impact wrench, on wedge anchors.
• Going too deep with screws. Tapcon says embedding deeper than 1-3/4" can make the screw bind in the hole.
• Anchoring out of square. Once it's bolted down, doors and vents will fight you forever. Check diagonals first.
• Forgetting drainage. On a full slab, water needs a way out.

How often should you check greenhouse anchors?

Check them at least once a year, and after any big storm. Fall is a good time, before winter wind and snow arrive.

1. Try each anchor by hand. Snug any that have loosened.
2. Look for rust on steel hardware. Replace rusty pieces with stainless steel.
3. Look for new cracks in the concrete near anchors.
4. Check that doors and vents still close smoothly. If they bind, the frame may have shifted.

Choosing a greenhouse for a windy or snowy site? Our list of the most durable greenhouses for wind, snow and harsh winters can help. You can also browse our full Riga greenhouse collection or the Cross Country Parkside 8x12.

Frequently asked questions