Screw piles in Batumi: for terraces, gazebos and light houses

What screw piles are suitable for

A screw pile is a steel tube with a helix at the end, screwed into the ground like a wood screw. It goes in within a day without concrete or heavy machinery, so it is handy where the load is light and you do not want to dig a pit: under a timber terrace, a gazebo or pergola, a carport, a garden store, a timber-frame sauna, a light timber-frame country house.

We do not put a masonry house by the sea on screw piles. A thin steel shaft rusts in wet salty ground, and the pile resists sideways movement poorly in an earthquake. For a house of blocks or cast-in-place concrete we use bored piles with ground beams.

Screw piles in Batumi: corrosion protection

By the sea the ground is damp all year and contains salt, so the life of a pile is set by how the steel is protected. We use piles with a thick shaft wall and a factory coating, preferably hot-dip galvanising. After installation the shaft is filled with cement grout: it pushes air and water out of the inside, and the tube can only rust from the outside. The cut above ground and the head plate are painted, and the section of pile at the boundary between ground and air, where corrosion is fastest, gets extra protection.

Cheap thin-walled piles with paint instead of zinc last noticeably less on the seafront than the building above them. So we write the make and wall thickness into the estimate and put the batch certificate into the project documents.

Ground and a trial pile

A screw pile needs ground the helix can grip: clay, loam, sand. In pebbles and rock the helix jams and tears, and in fill full of building rubble the pile goes in crooked. So on an unfamiliar plot we first screw in a trial pile and see at what depth the torque rises. For light buildings this is usually enough; for a timber-frame house the engineer asks for a ground survey.

If the trial pile hits rock at a shallow depth, it makes more sense to switch to a pier foundation or concrete footings.

Installation and the frame on top

We screw the piles in by hand with a lever or with a compact machine, keep them vertical with a level and make sure each one reaches the right ground. Then we cut the shafts to one level with a surveyor's level, fill them with grout and fit head plates. On top the piles are tied together by a frame of steel channel or glulam: without it the individual supports sway and the building settles unevenly.

Mistakes that make a building lean

• Piles screwed to the same depth regardless of the ground: some stand in the dense layer, some in fill, and the building settles unevenly.
• The shaft not filled with grout: condensation collects inside and the tube rusts from within.
• No frame, or one put together with self-tapping screws: the individual supports sway and the terrace deck skews over time.
• Head plates buried under soil or gravel: moisture stays against the steel all year round.
• Pile spacing taken by eye, without calculating the load from snow in the mountains or a heavy carport roof.

If there are already piles on the plot, we check their levels and the state of the cuts before building on top.

How much screw piles cost

A screw pile with installation and head plate costs from 300 ₾ each, and a frame of steel channel or timber from 110 ₾ per linear metre. For comparison, a reinforced concrete foundation pier is from 240 ₾ and a bored pile from 540 ₾. A 4×4 m gazebo usually needs 6–9 piles, a terrace along the house more; the number comes from a load calculation. The final cost is set after a trial pile on the plot and agreement on the estimate.