Modular Housing Development in Oeiras

Between December 2025 and March 2026, Rotopile built the deep foundations for a development of 14 modular houses in Leceia, Oeiras. The ground had a thick, highly variable fill layer, and modular construction called for speed: so helical piles were the main solution.

The fill ranged from 0.4 to 8.5 m thick across the site. Below it, the bedrock of the Lisbon Volcanic Complex, with pyroclastic rocks and basalts in a decomposed to highly weathered state. SPT tests showed medium-dense to very dense material beneath the fill, good for bearing once the surface deposits were passed. The wide variation in fill thickness called for a solution that could reach the competent strata at every point, under different loads.

For modules 5 to 12, Rotopile PRO400 and PRO250 helical piles were used, vertical and raked as the structural design required. 138 helical piles in all: 84 PRO400 (Ø88.9 × 9 mm shaft with a Ø400 × 10 mm helix, up to 150 kN) and 54 PRO250 (Ø88.9 × 9 mm with a Ø250 × 10 mm helix, up to 50 kN). Lengths ran from 2.0 to 9.0 m, depending on the fill thickness and the depth needed to reach the target torque and capacity. Installation used a 16-tonne excavator with Digga PD50 drive heads.

For modules 1 to 4 and 13 to 14, where conditions differed, a further 114 vertical micropiles were installed, in Ø88.9 × 9 mm tube 2.0 m long, by rotary-percussive drilling with a Comacchio MC 3D rig.

Helical piles brought clear advantages to a modular project, where the schedule is critical: fast installation, minimal ground disturbance, no major excavation and far less concrete than a conventional foundation. With no excavation spoil and less high-carbon material, the environmental impact was lower. And the flexibility of the system let the foundation adapt to the highly variable ground, carrying the loads down to the competent strata beneath the fill.

138 helical piles (84 PRO400 + 54 PRO250) + 114 micropiles · Ø88.9 × 9 mm · 2.0 to 9.0 m · 50 to 150 kN · 16 t excavator + Digga PD50