Logic ties and lags

The four ties, honestly used

Finish-to-start is the default and should dominate a healthy schedule — it says the work happens in sequence. Start-to-start and finish-to-finish model overlapping crews and are legitimate when the overlap is real. Start-to-finish is almost never the honest way to model construction work; when it appears, ask what it is doing.

When a lag is hiding an activity

A seven-day cure lag is fine. A forty-five-day lag labeled nothing is an invisible activity: it consumes time, carries no scope, shows no progress, and cannot be statused. Long lags are how work gets buried where reviews cannot see it. The discipline is simple — if it takes time and someone performs it, it should be an activity with a name, not a number on a relationship.

Negative lags (leads) deserve the same suspicion: "start the successor ten days before the predecessor finishes" is usually a modeling shortcut that scrambles the float math and confuses everyone reading the file.

What a reviewer checks

Reviews look at the proportion of non-FS ties, the count and size of lags, redundant relationships, and open ends — activities missing a predecessor or successor. High counts of any of these do not prove bad faith, but each one is a place where the printed dates and the real plan can quietly diverge.