All about the screw pile foundation

Screw piles, as soon as they appeared on the market, immediately established themselves well as supports for compact buildings and extensions. A terrace built on such stilts did not begin its journey away from the house, a bathhouse or barn did not fall to the side after a year or two, but stood as it was placed. In the last 7-8 years, screw piles have become quite widely used in the construction of frame houses – both small “modular buildings” and cottages with an area of 100-150 m2. Today, timber and log houses, and even foam block houses, are also built on such foundations.

A screw pile consists of a shaft (usually a steel pipe) and a lower blade, which ensures screwing into the ground and at the same time increases the load-bearing capacity of the pile. Sscrew piles are divided into narrow-bladed (with a ratio d/D = 0.6–0.8, where d is the diameter of the pile shaft and D is the diameter of the blade) and wide-bladed (d/D < 0.6). The former is intended for constructing foundations on dense clays and coarse soils, while the latter can be used on any other soil. In practice, narrow-blade multi-turn piles are also optimal for installing pillars that do not exert a significant compressive load on the ground (fences, pergolas, light canopies).

Design features

Screw piles make it possible to build a foundation in just a few days; moreover, it can immediately absorb the load from the building and is not afraid of the forces of frost heaving. Unlike shallowly buried tape and pillars, a pile-screw foundation on heaving soils does not make seasonal “jumps” up and down.

Advantages of a pile-screw foundation

Screw piles are produced by several dozen enterprises, including large factories and very small workshops. There is no single production technology or specialized standard for these products; as a result, products vary greatly in both price and quality. Here are the main parameters that you should pay attention to when choosing piles.

Criteria for selecting screw piles

The most common piles are made of St3 steel – not too hard and easily corroded, but the cheapest. Piles made of high-quality steel (grades 20, 25, 30, etc.) are more reliable – a thickness of 4–5 mm is sufficient here, provided there is good anti-corrosion protection. Stainless steel piles are designed to last for 60 years or more, but due to the very high price, their use is justified only when construction speed comes first – in other cases, a reinforced concrete foundation is more profitable.

Steel grade and thickness

The cheapest piles are those with one-sided protection with bitumen varnish or bitumen mastic – this coating is often applied directly on-site before installing the structure. And of course, in most cases, it is torn off by the pebbles contained in the soil when the pile is screwed in.

Corrosion protection method

1. Determination of pile pitch and planting depth 2. Installation 3. Concreting 4. Frame assembly 5. Creating a mock plinth

The process of installing a pile-screw foundation

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