This is a construction-progress story, not a fresh “project delayed again” announcement. That distinction matters for residents living along the corridor and drivers who have already spent years adapting to diversions. The new information is that difficult geology has forced slower, more precise excavation in several sections — particularly around Novena and Thomson — while LTA continues to work around active MRT lines, utilities and busy roads.
The good news is that some of the heaviest structural work is moving forward. LTA says more than 90% of foundations for the northern viaduct are complete, and construction noise is expected to reduce as foundation work winds down. But the corridor is still a live construction zone, and overnight closures continue at places such as Lentor Avenue.
01 · What has LTA revealed?
At a media briefing on 8 September, LTA described unexpected ground conditions uncovered as excavation progressed. In Novena, crews found a more complicated mix of hard rock and softer material instead of the more uniform clay conditions they had expected. In Thomson, the hard-rock layer was found nearer the surface and large boulders also appeared in the work zone.
These are not small inconveniences when construction sits beside live roads, buried utilities and an operating metro. LTA said earlier ground investigations were constrained by the existing urban environment, and some conditions could only be fully understood after excavation began.
02 · Novena: building around an operating MRT line
The Novena section is one of the most sensitive parts of the project because the road tunnel passes directly above and below the operational North-South MRT line. According to LTA’s briefing, the southbound tunnel section above the MRT tracks has been completed, while the northbound section beneath the line has been slower because of mixed rock and underground water seepage.
At one point, the active rail infrastructure is only about one metre above the excavation. That leaves very little room for error. LTA changed to a more precise sectional excavation approach, advancing in smaller increments of roughly two metres at a time rather than using the faster box-pushing method applied on the southbound side.
For passengers, the important point is that this is being engineered around a live MRT railway. The construction challenge does not mean a planned shutdown of the North-South Line has been announced. Residents should continue to use SMRT/LTA service notices for actual train disruptions rather than treating construction headlines as a rail-service alert.
03 · Thomson: hard rock and boulders are slowing foundations
In the Thomson area, LTA says the hard-rock layer was found around 10 metres closer to the surface than anticipated. Large boulders add another complication. Where a reinforced-concrete wall panel might normally take about a week to complete, some panels in difficult ground can take more than four weeks.
That helps explain why progress can look uneven from street level. A work site may appear unchanged for weeks even while crews are drilling, breaking rock, managing groundwater and installing structural elements below the road. It also explains why fixed end dates for individual traffic arrangements can change as underground conditions become clearer.
04 · Northern viaduct: more than 90% of foundations are complete
The northern viaduct around Gambas and Woodlands has faced a different mix of complications, including utility diversions and harder or higher rock than expected. Even so, LTA says more than 90% of the viaduct foundations are now complete.
Major viaduct segments are installed during short overnight windows — typically about four to five hours — to reduce disruption to daytime traffic and bus services. LTA says construction noise should generally ease as the heavy foundation phase winds down and traffic diversions are reduced.
That does not mean the corridor becomes quiet overnight. Lifting and installation work still needs controlled road space, so residents should expect some targeted night operations to continue while large structural sections are placed.
05 · Current road impacts residents should know about
The most useful source for day-to-day driving is LTA’s OneMotoring road-closure feed, because NSC works move through different stages and temporary traffic plans can change.
- Lentor Avenue: LTA lists daily closures affecting both bounds between the SLE and Yishun Avenue 1 from 1:30am to 5:30am, 1–30 September 2026, with different alternative routes depending on the approach.
- Additional Lentor/Sembawang closures: OneMotoring also lists selected dates — including 27 and 29 September — with a wider 1:00am–5:30am closure arrangement affecting parts of Lentor Avenue and Sembawang Road.
- Northern work zones: overnight NSC lifting and construction continues around the viaduct corridor. Check the live notice before driving because dates and route instructions are location-specific.
- Central sections: longer-running diversions around Marymount, Thomson and Novena remain tied to NSC construction, so drivers should follow current lane signs rather than relying on an old route screenshot.
If your trip is time-critical — airport, hospital, shift work or a fixed appointment — add margin during the overnight work window. The practical mistake is assuming a closure that did not affect you last week will still be configured the same way tonight.
06 · Has the North-South Corridor been delayed again?
No new delay has been announced. When asked whether the engineering challenges would affect completion, LTA said it is monitoring the progress of works and will give an update on the completion timeline “in due course”.
The agency’s current public project page still says the NSC is expected to open in phases from 2027: the viaduct from Admiralty Road West to Lentor Avenue is targeted for 2027, while the road tunnel from Lentor Avenue to the East Coast Parkway is targeted for 2029.
The project had already moved from its original 2027 completion target after Covid-era disruption. Until LTA publishes a new programme, it would be misleading to turn the September ground-condition briefing into another fixed delay claim.
07 · What the North-South Corridor will eventually become
The NSC is a 21.5km multi-modal transport corridor connecting northern Singapore with the city. It serves the wider Sembawang, Yishun, Ang Mo Kio, Toa Payoh, Novena and Rochor areas and is intended to relieve pressure on the CTE and other major north-south roads.
The corridor includes about 8.8km of viaduct and 12.3km of tunnel, with a short ground-level road section. The project is not simply a new expressway: LTA redesigned it as a transit-priority corridor, with existing surface-road space intended to support wider footpaths, cycling paths, bus-priority measures, greenery and community spaces after through traffic is shifted into the new tunnel and viaduct.
That future surface-street transformation is why the project matters beyond motorists. Neighbourhoods along the route are eventually meant to gain safer walking and cycling connections and more usable public space.
08 · What residents should expect over the next phase
For people living near the works, the next phase should be a mix: less prolonged foundation work in sections that are structurally advanced, but continued night possessions, lifting operations and local traffic switches as the corridor is assembled and connected.
Three practical habits help:
- Check OneMotoring before an overnight drive. Use the current notice, not an old social post or screenshot.
- Separate project news from service alerts. Engineering work near the MRT does not automatically mean train service is affected; follow LTA/SMRT for actual rail notices.
- Watch for official timeline updates. LTA has specifically said it will update the completion timeline in due course. Until then, 2027/2029 remains the published phasing.
09 · Why this update matters
Big infrastructure projects often disappear behind hoardings until a closure suddenly affects someone’s commute. This briefing provides a clearer explanation of why some NSC sections are moving more slowly than a surface observer might expect: the job is being built through complex geology while protecting operating rail, road and utility networks.
For residents, that context is useful — but it is not a blank cheque for vague timelines. The next genuinely important milestone is LTA’s promised programme update. That is the point at which residents will be able to judge whether the new engineering challenges change the existing 2027/2029 opening plan.
10 · Sources & verification
Fresh construction update: The Straits Times reported LTA’s 8 September 2026 media briefing on 12 September, including the Novena/Thomson ground conditions, excavation constraints, viaduct-foundation progress and LTA’s statement that it will update the completion timeline in due course.
Current official project status: LTA’s North-South Corridor project page continues to state phased opening from 2027, with the northern viaduct targeted for 2027 and the Lentor Avenue–ECP road tunnel for 2029. Official LTA material describes the corridor as 21.5km, including an 8.8km viaduct and 12.3km tunnel.
Current road closures: LTA OneMotoring was checked on 13 September 2026 for active NSC-related roadwork notices, including the September Lentor Avenue overnight closures. Road arrangements can change, so the live OneMotoring notice should take priority over this article for a specific journey.
- The Straits Times — LTA construction briefing, 12 Sep 2026
- Land Transport Authority — North-South Corridor project page
- LTA OneMotoring — current road closures and road works