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To a burglar with a hand truck, an unanchored safe is just a heavy box. Bolting it down stops the “carry it out and open it later” approach, and it also makes prying harder. Liberty Safe points out that prying a door is much easier when the safe can be tipped onto its back, and that a tall safe that tips over can seriously injure someone.
We covered where to put a safe in where to put a safe in your house. This guide covers how to bolt it down: what’s under your floor, which anchor to use, what to check before you drill, and when to call a professional.
This is general information. Your safe’s manual comes first. If it conflicts with anything here, follow the manual.
Before you start: read the manual and find the factory holes
Master Lock’s bolt-down guidance lists a few rules that apply to almost every safe:
- Confirm your safe is designed to be bolted down, and follow the instructions closely.
- Only use the anchor locations the manual shows. These are usually holes in the floor of the safe or its feet, and some safes have holes in the back.
- Don’t drill new holes in the safe. Master Lock says never to drill through the back of a fireproof safe, because that can ruin its fire protection.
- Don’t substitute parts for the recommended hardware.
Many safes hide the holes under a floor panel or carpet. On Liberty safes, for example, you lift the floor panel and pop out caps to reach pre-cut holes.
What to look for: a safe anchor bolt kit matched to the manufacturer’s hole size.
See safe anchor bolt kits (paid link)
Step 1: Figure out what you’re drilling into
Liberty Safe notes that the anchor depends on the subfloor, not the floor covering. Here’s a quick way to tell:
- Slab on grade, garage, or basement floor: almost always concrete.
- Main floor over a basement or crawlspace, or any upper floor: usually plywood or OSB on wood joists.
- Tile: Liberty says you can’t anchor a safe through tile, because bolting down puts enough pressure on it to crack it. Ask an installer about options.
Step 2: Safety checks before drilling
This is the step people skip, and it’s the one that causes the expensive mistakes.
Post-tension slabs. Some slabs have steel cables inside under very high tension. Liberty Safe says these slabs are usually stamped with a warning not to drill, cut, or core, and a cut cable can snap out of the concrete and hurt someone. If you see that stamp, or aren’t sure, stop and call a pro who can scan the slab.
Radiant floor heat. Liberty’s installation guide says not to drill a radiant-heat or post-tension slab until you’ve confirmed what’s in it and where. A case study from the Infraspection Institute shows that infrared (thermal) imaging can map heating tubes under concrete before drilling. Professional concrete scanners also offer this service.
Plumbing, wiring, and ducts. For wood floors, check from below. Go into the basement or crawlspace and look for pipes, wires, and ductwork under your planned holes. On slabs, look for nearby floor drains, plumbing walls, and outlets that hint at lines in or under the slab. If you can’t confirm a spot is clear, move the safe or get help.
Moisture. Liberty says concrete gives off moisture that can corrode the safe and the anchors. It suggests a hard rubber mat under the safe or sealing the slab with epoxy, plus anchors that are at least galvanized or zinc-plated. If anything in the safe is moisture-sensitive, see our document protection guide.
Step 3: Choose the right anchor
Concrete: wedge anchors vs. sleeve anchors
| Wedge anchor | Sleeve anchor | |
|---|---|---|
| How it holds | A clip at the bottom expands when you tighten the nut | A full-length sleeve expands along the hole |
| Base material (per Simpson Strong-Tie) | Solid concrete or grout-filled masonry | All types of solid base materials |
| Typical safe use | Poured concrete slabs | Solid masonry such as brick, or where the safe maker’s kit specifies them |
Both install the same basic way. Simpson Strong-Tie’s instructions:
- Drill with a carbide bit the same diameter as the anchor, to the specified depth (or deeper, to leave room for dust).
- Blow the hole clean with compressed air.
- Put the anchor through the safe’s hole and tap it in until the washer and nut sit tight.
- Tighten to the specified torque. Simpson says not to use an impact wrench, and warns that an oversized hole makes the anchor hard to set and lowers its holding power.
Simpson’s data also lists edge-distance and spacing adjustments, so anchors set too close to a slab edge or to each other hold less. Many safe makers sell kits with matched anchors. Liberty’s concrete kit, for example, uses a 3/8-inch masonry bit and a hammer drill.
What to look for: a zinc-plated wedge anchor kit for concrete and a hammer drill with carbide masonry bits.
See zinc-plated concrete wedge anchor kits (paid link)
See hammer drills and carbide masonry bits (paid link)
Wood: lag bolts into joists
On wood, use lag bolts with washers, driven into joists, not just the subfloor. Liberty’s guide says to avoid anchoring only into thin subfloor when you can.
How to do it:
- Find the joists with a stud finder, or by measuring from a known point in the basement or crawlspace below.
- Position the safe so as many anchor holes as possible line up over a joist. You may have to shift it a few inches.
- Drill pilot holes at the size the kit specifies. Liberty’s wood kit calls for 1/4-inch holes and a 9/16-inch socket.
- Drive the lag bolts with washers, snug but not stripped.
If no hole lines up with a joist, don’t settle for subfloor only. Ask an installer about options, such as adding solid blocking between the joists from below.
What to look for: a lag bolt and washer kit for anchoring a safe to a wood floor.
See lag bolt and washer kits for safe anchoring (paid link)
Step 4: Set, level, and tighten
- Mark the holes. Set the safe in place and mark through its anchor holes with a long marker or punch. Then move the safe aside to drill. Having a second person makes this safer.
- Drill, clean, and test-fit the anchors.
- Move the safe back and shim it level if the floor isn’t flat. A level door closes and latches correctly.
- Tighten in a cross pattern, the way you’d tighten a wheel’s lug nuts, so the safe pulls down evenly.
- Reinstall the floor caps or panel, and seal the holes if the manual says to.
- Open and close the door several times. If it rubs or won’t latch, a corner was pulled out of level.
Common mistakes
- Using fewer anchors than the safe has holes.
- Hitting only subfloor on a wood floor.
- Oversized or dusty holes in concrete, which Simpson warns reduce holding power.
- Over-torquing with an impact wrench, which Simpson specifically warns against.
- Drilling an unknown slab without checking for post-tension cables or radiant tubing.
- Skipping the door test. If the door binds after tightening, the safe has been pulled out of level.
When to hire a professional
Liberty Safe recommends professional installation unless you have experience moving and installing safes, and says professional installation keeps its safes’ warranty intact. Hire one if:
- The safe is large or heavy. Higher-rated safes often assume anchoring or a lot of weight. TL-rated safes must weigh at least 750 lbs or be anchored, and per SafesPick’s summary of UL 1037, RSC Level II safes must weigh 750 lbs or be anchorable.
- It’s going on an upper floor, where load and joist placement matter.
- You find a post-tension stamp, radiant heat, or tile.
- You don’t own a hammer drill or aren’t comfortable with one.
A safe technician or installer can also add wall anchoring where the maker allows it.
Renters and other limits
If you rent, drilling the floor usually needs written permission. See our renter-friendly guide to securing valuables for options.
Bottom line
Read the manual, find out what’s under the floor, and check for cables, tubing, pipes, and wires before you drill. Use wedge anchors in solid concrete or lag bolts into joists, install them exactly to spec, and use every hole. An hour of careful work keeps a thief from simply wheeling your safe away. If you’re also choosing a lock, our safe lock types guide covers the options.
Sources
- Master Lock — Do’s and Don’ts of Bolting Down a Safe. https://www.masterlock.com/insights/bolting-down-your-safe-for-an-added-layer-of-protection
- Liberty Safe — Anchoring Your Gun Safe to the Floor (tipping and prying, subfloor types, wood and concrete steps, tile, pro installation). https://libertysafe.com/blogs/the-vault/anchoring-your-gun-safe-to-the-floor
- Liberty Safe — Your Gun Safe and Concrete Floors (post-tension slabs, concrete moisture, anchor coatings, rubber mat or epoxy). https://libertysafe.com/blogs/the-vault/your-gun-safe-and-concrete-floors
- Liberty Safe — Builder-Friendly Small-Space Safe Installation Tips (radiant heat and post-tension checks, joists vs. subfloor). https://libertysafe.com/blogs/the-vault/builder-friendly-small-space-safe-installation-tips-without-compromising-security
- Simpson Strong-Tie — Wedge-All Wedge Anchor catalog pages (base materials, installation steps, no impact wrench, oversized holes). https://bristolmachinecompany.com/wp-content/uploads/2019/01/Simpson-Strong-Tie-Catalog-Wedge-All.pdf
- Simpson Strong-Tie — Sleeve-All Sleeve Anchor product data (base materials, installation, edge distance and spacing). https://www.buildsite.com/pdf/simpsonstrongtie/Sleeve-All-Sleeve-Anchor-Product-Data-2420716.pdf
- Infraspection Institute / W. Swirnow — Thermography Inspection of In-floor Radiant Heating Systems — Case Study. https://irinfo.org/images/articles/pdf/05-01-2015-swirnow.pdf
- Blue Dot Safes — Understanding Burglary Ratings (TL 750 lb / anchoring requirement). https://bluedotsafes.com/wp-content/uploads/2025/01/Understanding-Burglary-Ratings.pdf
- SafesPick — Gun Safe Test: What UL, ETL and In-House Tests Mean (UL 1037 RSC Level II weight/anchoring requirement). https://safespick.com/guides/gun-safe-testing/