Complete technical package
One coordinated scope: soil data, foundation calculations, structural drawings and technical substantiation.
Small Rear Extension • Foundation Calculations • Soil Investigation • Pile Plan
Small Rear Extension: foundation calculations, soil investigation & pile plan
Planning a small rear extension and need a safe, municipality-ready foundation design? Aboss delivers a complete technical package including soil investigation coordination, foundation calculations, a pile plan where required, and the structural drawings needed for construction and permit submission.
This is particularly relevant for narrow urban plots, tight property boundaries and extensions that must tie into an existing house without causing settlement issues, structural conflicts or unnecessary permit delays.
Amsterdam & region • Den-Haag • Rotterdam • Groningen • Deventer
Typical scope: soil data, foundation concept, structural calculations, execution details and permit-ready substantiation.
Designed for constrained sites
Optimised for limited width, tight boundaries and sensitive interfaces with existing urban buildings.
Clear permit-ready output
Practical documentation that reduces follow-up questions from contractors and municipality reviewers.
What we deliver
- Soil investigation coordination: planning, scope alignment and interpretation of results.
- Foundation calculations: bearing capacity, settlement risk, load transfer and interaction with the existing building.
- Pile plan where required: pile positions, preliminary sizing, pile loads and structural layout logic.
- Structural drawings and details: foundation plan, sections, connections, beams or steel where needed, and execution notes.
- Municipality-ready technical substantiation: clear narrative and calculation report suitable for permit submission.
Typical small extension constraints we account for
- Limited width and short spans, but high sensitivity to differential settlement.
- Proximity to neighbours and existing foundations.
- Existing house structure, load paths and wall openings.
- Execution practicality on constrained urban sites.
Process: efficient and controlled
1 — Intake and available information
We review your extension concept, approximate dimensions, photos and any existing drawings. Previous reports, foundation information or architectural plans are especially useful.
2 — Soil investigation
If needed, we coordinate the soil investigation and define the appropriate scope. The results are then interpreted in the context of your building, your extension loads and the surrounding site conditions.
3 — Foundation concept and calculations
Based on ground parameters and structural loads, we develop a feasible foundation concept and substantiate it with calculations for safety, stability and serviceability.
4 — Pile plan and execution drawings
Where piles are required, we prepare the pile plan and detailing so the contractor can execute reliably and the municipality can assess the proposal logically.
5 — Final file for permit and construction
You receive a clear package in PDF and, where agreed, DWG. This can be used both for contractor execution and municipality submission.
Why soil investigation matters
A small rear extension may look modest, but foundation design is often the most sensitive technical element. In Dutch urban soils, seemingly small differences in ground conditions can lead to settlement, cracking or differential movement if the wrong foundation strategy is chosen.
- Soil investigation helps determine bearing layers and feasibility of piles or strip foundations.
- It improves insight into settlement risk and structural interaction with the existing building.
- It supports clear design decisions instead of assumption-based construction.
- It strengthens the permit file when technical substantiation is requested.
Especially in Amsterdam and similar urban conditions, correct interpretation of soil data can prevent costly redesign or execution problems later.
Typical situations for a small rear extension
Example situations include tight rear gardens, constrained access, close neighbouring foundations, and extensions that require careful connection to existing walls, beams or floor levels.
FAQ
What is a pile plan and when do I need it?
A pile plan defines pile positions and load distribution logic for the extension foundation. It is typically needed when the soil profile requires deep foundations, when loads are significant, or when settlement risk needs to be controlled carefully.
Can you also provide structural calculations for the superstructure?
Yes. If the extension includes steel beams, wall openings, roof structure or specific framing, we can integrate the full structural scope into one coordinated package.
Do you only work in Amsterdam?
We primarily work in Amsterdam and the surrounding region, but we also support projects in other municipalities. The package can be aligned to the local review context.
What should I send for a quick intake?
Please send a short description, address, approximate extension dimensions, photos and any existing drawings or reports. That allows us to indicate quickly what is required and prepare a clear quote.
Contact Aboss
Send your address, a short project description, approximate extension dimensions, photos and any available drawings. We can then indicate quickly whether soil investigation, pile plan, calculations and drawings are needed, and prepare a clear quote.