The increasing demand for sustainable and easily constructible housing has led to the exploration of alternative foundation systems for lightweight modular structures. This research investigates the feasibility of using short helical piles to support a lightweight wooden building, assessing its settlement behaviour and structural integrity over time. Unlike traditional deep pile foundations, short helical piles are designed to be easily installed, removed, and reused, offering both environmental and economic advantages. However, their application in soft soils raises concerns regarding excessive and differential settlement.

The main research question for this thesis is:
”What is the structural feasibility of a lightweight, modular wooden building design on short, screwed foundation piles that is expected to have large amount of settlement?”
To answer this question, a literature study was done in combination with a case study. The literature established the boundary conditions for the use of helical foundation piles and explores the expected capacity and settlement behaviour in soft soil. Afterwards, it focusses on aspects such as decay and modular systems of timber construction elements.
With the knowledge obtained from the literature, a case study was developed. To investigate the behaviour of a lightweight structure that is expected to settle, a numerical modelling approach is used, combining PLAXIS 2D and SCIA Engineer. PLAXIS 2D was used for simulating the settlement behaviour of the structure at multiple stages in time, while the effect of these settlements on the superstructure was analysed in SCIA Engineer. Different wall systems were investigated, focusing on the influence of the wall stiffness, varying pile capacities, and the impact of uneven loading. Time-dependent settlement effects were evaluated at time stages just after the completion of the construction and at three additional points further in time. This provides insight on the short-term and long-term behaviour of the structure. To prove that a structure of this typology is sufficient for housing, it is tested on total settlement (𝑈), differential rotations (𝛽), tilt (𝜔), and element capacity (𝜎).

The results of the calculations indicate that for a lightweight, timber structure placed on short helical piles large amount of settlement can be expected when positioned in soft soil. However, the settlements will not lead to a significant stress increase that causes failure of structural elements. A stiffer wall system has the ability to redistribute more force to the foundation piles at the most outer position. This reduces the differential settlement between piles, but also reduces the maximum total settlement of the wall. The resistance to deformations of the outer foundation piles is therefore more impactful with a stiffer superstructure. In general, the findings suggest that with careful consideration of settlement behaviour, short helical piles can be a viable foundation solution for supporting lightweight houses.