Phase 0 foundation survey
A fast and affordable way to identify the risk of foundation problems. Increasingly important when buying or selling a home — and mandatory for property valuers from 1 April 2026.
Check the foundation risk of your home for free
Enter your address and get an indicative risk assessment based on construction year, soil type, groundwater level and subsidence.
What is a Phase 0 foundation survey?
A Phase 0 foundation survey is the first and most accessible step in foundation research. Instead of immediately digging costly trial trenches, a certified inspector assesses in 30 to 60 minutes whether there is an elevated risk of foundation problems.
The methodology was developed by NAFO (Dutch Association of Foundation Researchers) and combines the KCAF QuickScan with visual inspection and measurements inside and outside the home. The survey is non-destructive: nothing is dug up, drilled or demolished.
The result is an official NAFO certificate with one of four outcomes: no action needed, monitoring, Phase 1 survey recommended or required. This certificate is accepted by valuers, lenders and the NWWI.
When is a Phase 0 survey needed?
A Phase 0 survey is recommended in the following situations:
- When buying a home — especially if the property is from before 1970, sits on peat or clay soil, or lies in a designated risk area.
- When selling a home with elevated foundation risk, so you don't get surprised in the valuation phase.
- When the valuer flags a high foundation risk during the purchase based on the central foundation database.
- With visible signs: cracks in walls, sticking doors or windows, tilting, cracking around frames.
- As an owner of an older property who wants to periodically monitor whether the foundation is still in order.
Mandatory for property valuers from 1 April 2026
From 1 April 2026, NRVT-registered property valuers must include foundation information in their valuation report. If the valuer flags an elevated foundation risk based on the central foundation database, a Phase 0 survey becomes a mandatory part of the file.
As a seller, you can stay ahead of this: have a Phase 0 survey carried out yourself to avoid surprises and delays in the sales process.
What is examined?
The Phase 0 survey consists of four parts that together provide an objective picture of the foundation risk:
01
Visual inspection
The inspector assesses cracking, deformation, sticking doors and windows, and other visual signals on both the inside and outside of the home.
02
Measurements
Mortar joint measurements for tilting, level measurements for settlement, and slopes of floors and façades. Everything is photographically documented.
03
Surroundings analysis
The inspector assesses environmental factors such as nearby trees, basements, subsidence in street and garden, new-build projects and recent works in the area.
04
Desk research
Construction year, foundation type, soil map, groundwater table and KCAF risk areas are consulted to determine the indicative risk class.
Five factors that determine foundation risk
Together these factors determine the chance of foundation problems. Our online check combines them into an indicative risk class A to E.
Construction year
Homes from before 1970 often have wooden foundation piles that are sensitive to dry standing and fungal decay. The risk is highest for properties from the 19th and first half of the 20th century.
Soil type
Peat soil is highly compressible and gives the highest risk of uneven settlement. Clay has a moderate risk due to shrinking and swelling. Sandy soil is stable.
Groundwater level
A low groundwater level (more than 140 cm below ground) causes wooden piles to dry out and leads to pile rot. This is one of the main causes of foundation problems.
Subsidence
Strong subsidence (more than 2.5 mm/year) can lead to cracks in walls, sticking doors and windows, and damage to the foundation.
Risk area
The Knowledge Centre for Foundation Issues (KCAF) has mapped areas with known elevated risks. If your home is in one, additional research is recommended.
The NAFO certificate: four possible outcomes
After the survey you receive an official NAFO certificate within a few business days, with one of these conclusions:
No action needed
There are no concerning signals. You can leave the foundation out of consideration.
Monitoring recommended
There are points of attention, but no acute problem. Periodic monitoring is sufficient.
Phase 1 survey recommended
There are signs of possible issues. A more extensive Phase 1 survey with trial trenches gives more certainty.
Phase 1 survey required
There are clear signs of foundation problems. Immediate follow-up research is needed to determine the scope.
What does a Phase 0 survey cost?
Combined with a building inspection
€ 200 – € 300
The inspector is on site anyway, so the survey can be carried out at a reduced rate.
As a standalone survey
€ 350 – € 495
Excluding building inspection, focused only on the foundation. Suitable for owners who only want the foundation assessed.
Duration: the on-site survey takes 30 to 60 minutes. You usually receive the NAFO certificate and underlying report within 48 hours to a few business days after the inspection.
Want to check the risk online first?
Our free check combines construction year, soil type, groundwater level, subsidence and KCAF risk area into an indicative risk class. So you'll instantly know whether an on-site Phase 0 survey is worthwhile.
Difference between Phase 0, Phase 1 and Phase 2
Foundation research is organised in three escalating phases. Each phase has its own purpose, depth and price tag:
Phase 0
Risk assessment
€ 200 – € 495
- Duration
- 30-60 min on site, report within 48 hours
- Method
- Non-destructive — visual inspection, measurements and data analysis
- End result
- NAFO certificate with indication and advice
Phase 1
In-depth survey
€ 3,000 – € 6,000
- Duration
- 3-4 weeks including report
- Method
- Trial trench, pile head inspection, wood samples
- End result
- Report with condition per pile and need for repair
Phase 2
Specialist survey
€ 8,000 +
- Duration
- 6+ weeks, depending on scope
- Method
- Soil and bearing capacity research, structural calculations
- End result
- Repair plan and cost estimate for foundation restoration
Sources: NAFO, KCAF, NRVT. The HuisAssist online check provides an indicative risk assessment based on public data (BAG, BRO, GeoTOP, KCAF, SkyGeo subsidence map) and does not replace a professional Phase 0 survey. Always consult a certified foundation specialist for a definitive assessment.
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