New build inspection · Foundation and basement
Foundation and basement defects in a new build
The foundation is the one part of the house covered by the longest warranty period and the one most buyers never see, because it is backfilled within days of being poured.
What goes wrong with foundation and basement in a new build?
Reviewed · 2026-09-03The foundation is the one part of the house covered by the longest warranty period and the one most buyers never see, because it is backfilled within days of being poured.
Why it matters
Foundation and basement in a new home
A poured concrete foundation is visible for a very short window. It comes out of the forms, gets damp proofed and a drainage membrane, and is buried. If you are buying a home still under construction, the few days before backfill are worth a site visit, because nothing below grade can be checked afterwards without excavation.
Concrete cracks. That fact alone is not a defect, and a builder telling you so is not brushing you off. What matters is the type of crack, whether it is moving, and whether water is coming through it. A narrow vertical shrinkage crack in a basement wall is ordinary. A diagonal crack at a corner that grows over a winter is not.
Calgary adds two local factors. Expansive clay soils move seasonally with moisture, which stresses foundations and slabs. And Alberta has some of the highest indoor radon levels in the country, which is why the building code requires a rough-in for a future radon system in new homes.
Best moment to look
Excavation and foundation
Before backfill you can see the damp proofing, the drainage membrane, the weeping tile and the pipe penetrations. After backfill you are limited to what shows from inside the basement.
In Alberta
Health Canada testing has repeatedly found Alberta among the provinces with the highest proportion of homes above the national radon guideline, and the Alberta Building Code requires a radon rough-in in new residential construction. A rough-in is not a mitigation system: it is the pipe that makes one cheap to add later. Test your finished home over at least three months in the heating season, and keep the rough-in accessible when you finish the basement. Structural defects in the foundation fall under the longest coverage period of the Alberta New Home Warranty, which is why documenting cracks early is worth the effort.
The flags
What to look for
Each item lists what the defect is, how to spot it without tools, and the stage of construction when it is still visible. None of this replaces a licensed inspector. It makes you a useful witness on your own site.
01Damp proofing missed at corners and penetrations
Water and envelopeWhat it is. The black coating on the outside of the foundation is the primary barrier against soil moisture. It is sprayed quickly, and corners, form-tie holes and pipe penetrations are the spots that get missed.
How to spot it. Before backfill, walk the perimeter and look for bare grey concrete showing through, especially at inside corners and around any pipe passing through the wall.
Visible at: Excavation and foundation
02Weeping tile installed without protection or fall
Water and envelopeWhat it is. The perforated pipe at the footing carries groundwater to the sump. If it is laid without clean gravel and a filter membrane, silt fills it, and a blocked weeping tile cannot be cleaned once buried.
How to spot it. Before backfill, look for the pipe sitting in clean washed rock, wrapped or covered by filter fabric, and running continuously around the footing rather than in disconnected lengths.
Visible at: Excavation and foundation
03Diagonal or stepped cracking at openings and corners
StructuralWhat it is. Vertical hairline cracks from shrinkage are ordinary. Diagonal cracks radiating from a window corner, or stepped cracking in block, suggest differential movement rather than curing.
How to spot it. Inspect the inside face of the basement walls before they are finished. Photograph any crack with a ruler or a coin for scale and re-photograph the same crack after the first winter.
Visible at: Pre-drywall
04No radon rough-in, or a rough-in that goes nowhere
SafetyWhat it is. Alberta requires new homes to include a rough-in for a future radon mitigation system: a sealed pipe from below the slab, capped and labelled, ready to be fitted with a fan. It is frequently installed incorrectly or left unlabelled.
How to spot it. Look in the basement or mechanical room for a capped pipe stub, usually labelled, running from the slab upward. Ask where it terminates and whether it is sealed at the slab.
Visible at: Pre-possession walkthrough
05Sump pit without a pump, lid or alarm
SafetyWhat it is. Many builders provide the pit and leave the pump as an upgrade. A pit with no pump is a hole that fills. An uncovered pit also vents soil gas, including radon, directly into the basement.
How to spot it. Open the sump lid. Confirm there is a pump, that it is plugged into a dedicated receptacle, that the lid seals, and that the discharge line runs outside.
Visible at: Pre-possession walkthrough
06Slab cracking with vertical displacement
StructuralWhat it is. Basement slabs crack as they cure and that is normal. A crack where one side sits higher than the other indicates soil movement below the slab, which matters in Calgary clay.
How to spot it. Run a foot or a straight edge across any slab crack before flooring goes down. You are feeling for a lip, not just a line.
Visible at: Pre-drywall
Put it in writing
Questions for the builder
Ask these by email rather than on site. A written answer is a record, and a builder who answers clearly in writing is telling you something useful about how the rest of the build will go.
- Can I visit the site after the foundation is poured but before backfill?
- Where does the radon rough-in terminate, and is it sealed and labelled?
- Is a sump pump included, or is the pit supplied empty?
- What soil conditions were found on this lot, and did they change the foundation design?
FAQ
Questions about foundation and basement
Narrow vertical cracks from concrete shrinkage are common and usually not a structural concern. Diagonal cracks from window and door corners, stepped cracks, horizontal cracks, and any crack that leaks water or grows over a season are worth reporting. Photograph every crack with something for scale on the day you find it, then again after the first winter, so you can show movement rather than argue about it.
It is a capped pipe running from beneath the basement slab, installed so a mitigation fan can be added later without breaking concrete. It does nothing on its own. The next step is to test the finished home with a long-term radon test through the heating season. If the result is above the Canadian guideline, the rough-in makes the fix straightforward.
Alberta new home warranty coverage is layered, with the longest period applying to structural defects in the building envelope and load-bearing elements, and much shorter periods for workmanship, materials and distribution systems. Confirm the exact periods and start dates on your own warranty certificate, because coverage runs from defined dates rather than from when you notice a problem.
Source note
- Sources
- Alberta New Home Warranty program information
- National Building Code, Alberta Edition, as adopted for the permit in force
- City of Calgary building inspection and lot grading information
- Health Canada radon guidance for homeowners
- Jurisdiction
- Alberta, with Calgary-specific notes
- Applies to
- New residential construction purchased from a builder.
- Last reviewed
- 2026-09-03
- Limitations
- General guidance written for buyers, not a code interpretation and not a substitute for a licensed home inspector or a professional engineer. Code requirements depend on the edition in force when the permit was issued. Warranty periods and coverage depend on your own warranty certificate.
- What you should verify
- The requirements that applied to your permit, the coverage periods on your warranty certificate, and any defect with a licensed inspector before you rely on it in a claim.
Work with REP YYC
Bring your own representative to the walkthrough.
The builder's sales staff are paid to sell the builder's lots. REP YYC agents are paid by the builder too, but they work for you: lot choice, contract terms, incentives and the possession timeline. No cost to the buyer.