A concrete tiki torch combines a tall, slender concrete casting with a fuel cup and wick, and it does double duty in a yard: it lights the space after dark, and the smoke from the flame helps keep mosquitoes away. The build uses a section of PVC pipe as both the form and the permanent socket for the fuel cup, which keeps the casting process simple. The techniques for mixing, placing, and curing the concrete are the same ones used in larger DIY concrete projects for homeowners, scaled down to a single slender column.
Planning the Torch Design
A torch that looks right in a garden bed stands 90 to 120 cm tall, tall enough to clear plants and seating but short enough to fill easily. The proportions come from the PVC pipe, the concrete shell, and the fuel cup that sits on top.
Height and proportions
The concrete column should make up roughly one-third of the total height, with the fuel cup and flame accounting for the rest. A 10 cm diameter column reads as solid from a distance, while a 7.5 cm pipe keeps the torch lighter and easier to move. Tapered forms are possible but require more elaborate molds and bracing.
Choosing the fuel cup and wick
Tiki torch fuel cups are metal or ceramic vessels that hold a wick and a reservoir of fuel. A metal cup with a threaded base screws into a fitting embedded in the concrete, which makes replacement easy when the cup corrodes. Ceramic cups sit in a recess cast into the top of the column. The decorative finish of the surrounding concrete can echo the patterns used for decorative concrete tiles, from smooth rubbed surfaces to lightly textured bands.
Sizing the wick for the cup
The wick should reach from the bottom of the fuel reservoir to about 1 cm above the cup rim. A wick that is too short starves the flame of fuel, while one that is too long burns with a tall, smoky flame. Fiberglass wicks outlast cotton wicks in outdoor use.
| Cup diameter | Reservoir volume | Wick length | Typical burn time |
|---|---|---|---|
| 5 cm | 150 ml | 12 cm | 2 to 3 hours |
| 7.5 cm | 250 ml | 15 cm | 3 to 4 hours |
| 10 cm | 400 ml | 18 cm | 4 to 6 hours |
Concrete Mix for Tall Slender Castings
A torch column is a vertical, unreinforced concrete element with a small cross-section, so the mix has to be cohesive enough to hold together when the form is stripped and strong enough to resist handling. A stiff mix that works in a wide form will leave voids in a narrow column.
Mix design for vertical pours
Use a 1:2:2 mix by volume, one part cement, two parts sand, and two parts small aggregate with a maximum size of 10 mm, at a water-cement ratio of about 0.45. For a smooth exterior, cast a first layer of mortar in the form, then fill the core with the aggregate mix. The mortar skin gives the column a finished face without a separate rubbing step.
Strength and testing
A column cast at a 0.45 water-cement ratio reaches a 28-day compressive strength of roughly 25 to 35 MPa, more than enough for a freestanding garden element. The standard way to verify concrete strength is the cube compression test, and the reason laboratories use 150 mm concrete cube samples for compression testing is that larger cubes give more reliable results with normal aggregate sizes.
Why water control matters
Extra water is the most common cause of weak concrete in small castings. Each additional liter of water per 50 kg bag lowers strength measurably and increases shrinkage, which shows up as surface crazing on a smooth column. Mix to a firm, cohesive consistency, not a soupy one.
Building the PVC Formwork
PVC pipe does two jobs in this project: it forms the concrete into a cylinder, and it can stay in place as the socket that holds the fuel cup assembly. Schedule 40 pipe is rigid enough to hold its shape under the pressure of wet concrete.
Pipe as both mold and permanent insert
Cut the pipe to the column height plus 5 cm. If the pipe stays in the concrete, the fuel cup fitting sits inside the pipe at the top and the concrete fills around it. If you want a bare concrete column, wrap the pipe in tape and pull it out after the concrete firms up, leaving a smooth cylindrical socket.
Sealing and bracing the form
Seal the bottom of the pipe with a cap, a plug, or a plastic plate taped in place so wet concrete cannot leak out. Brace the pipe vertically with a stake and a clamp so the pour does not push it out of plumb. The same rules for working concrete into tight spaces apply here, and the techniques for consolidating concrete in congested reinforced members are exactly what a narrow pipe demands.
- Cut the pipe to length and seal the bottom.
- Set the pipe plumb on a flat, level base.
- Clamp or stake the pipe so it cannot move during the pour.
- Insert the fuel cup fitting at the top, centered in the pipe.
- Mix the concrete in small batches so it stays workable.
Pouring, Consolidation, and Curing
Pour the concrete in layers no deeper than 15 cm, rodding each layer with a length of rebar or a wooden dowel to release trapped air. A narrow column traps air easily, and air voids at the surface show up immediately after stripping.
Layered placement
Work around the fitting at the top of the pipe carefully so it stays centered. Tap the outside of the pipe with a rubber mallet after each layer; the vibration settles the paste against the form and closes surface voids. Stop the pour 1 cm below the top of the pipe so the rim of concrete stays hidden.
Curing a vertical casting
Leave the torch in the form for 48 hours, then strip the pipe if it is a temporary form. Keep the concrete moist for 7 days by wrapping it in wet burlap or plastic sheeting. The column gains about 70 percent of its 28-day strength in the first week, and early moisture is what lets that strength develop. If you later set the torch on an existing concrete pad, prepare the surface with the bonding rules for pouring new concrete over an old concrete surface so the base does not separate.
Mounting the Fuel Cup and Wick
The fuel cup has to sit securely on the column, because a torch that tips spills burning fuel. A threaded metal cup screwed into a fitting embedded in the concrete is the most secure arrangement.
Setting the cup before or after casting
Embed the fitting in the wet concrete for a permanent installation, or cast a recess and set the cup with a removable sleeve for easy replacement. Either way, the cup must stand level, because a tilted cup lets fuel pool at one edge of the wick.
Wick preparation and fuel rules
- Fill the cup to three-quarters full with torch fuel designed for outdoor lamps.
- Wait 20 minutes after filling so the wick soaks before lighting.
- Never add fuel to a hot or lit torch.
- Extinguish by snuffing the flame; do not blow it out.
- Store fuel away from the torch and out of reach of children.
Before the first lighting, go through the checks in post-concrete inspection and testing to catch cracks or soft patches that would get worse under heat.
Placement, Maintenance, and Long-Term Care
A concrete torch is heavy enough to stand on its own, but placement decides how safely it burns. Site it on level, non-combustible ground, away from overhanging branches, and at least 3 m from structures and seating.
Siting torches outdoors
- Keep at least 3 m from house walls, decks, and dry vegetation.
- Set the torch in a bed or on pavers, never in tall dry grass.
- Place torches where the flame is visible but not under a canopy.
- Angle the torch away from walkways so a gust cannot push flame toward passers-by.
Seasonal care
Inspect the concrete for hairline cracks before each season and seal the column with an exterior concrete sealer every 1 to 2 years. Clean the fuel cup and replace the wick when it frays. In freezing climates, drain the fuel and store the torch upright under cover, because water trapped in the cup can freeze and crack the concrete.
The column is a small-scale version of a structural member carrying a live load, and understanding how concrete handles compression explains why the torch works: concrete is strong in compression and weak in tension, which is why reinforcement appears wherever concrete is asked to bend. The detailed analysis of prestressed concrete over reinforced concrete walks through those material limits and the design responses to them.