Three numbers that tell you how a Revit model is ageing
Nobody opens the warnings list on a Wednesday. Quite right too. Then one day it is four thousand entries long and the model takes nine minutes to open.
Revit models do not slow down overnight. They slow down over months, in ways nobody notices until a deadline makes them impossible to ignore. By then the options are all bad ones: work late, split the model, or lose a morning to an audit that should have happened in March.
Three numbers predict most of it. None of them takes longer than a minute to find.
1. Central file size
Sync time and open time track file size closely. Every sync moves data between a person's local file and the central model, so a project that has doubled in size has roughly doubled the cost of every sync, for every person, several times a day.
Watch the trend rather than the number. Steady growth as the design develops is healthy. A jump of forty per cent in a fortnight usually means the model has swallowed something: a survey that was bound instead of linked, a consultant's CAD file arriving with every layer of their title block, a photograph of a material sample at full camera resolution.
- Purge unused on a detached copy first, so you can see what goes before it goes
- Check for bound links that ought to still be links
- Look inside families for imported CAD, which multiplies quietly
2. Warning count
Warnings are not errors, which is exactly why they accumulate. Revit tolerates them and keeps re-evaluating them, so a list in the thousands becomes a tax on everything the model does.
It is also a record of decisions nobody quite made: overlapping walls, duplicate instances, elements a few millimetres off axis, room separation lines left behind by a plan that changed. A few hundred on a live project is ordinary. Several thousand means the list stopped being read and a warning nobody reads has stopped being a warning.
- Fix by category rather than by line. Sort, clear the biggest group, re-count
- Agree a ceiling per project and write it into the practice standard
- Do it monthly. Doing it once at Stage 4 costs a week nobody has
3. Worksets open at load
Revit loads what it is asked to load. Someone opening everything on a large project pulls in the structure, the services, the site and a set of linked models they will not touch all day. Memory fills, the machine starts swapping and the ticket that reaches us says "my computer is slow".
The useful question is whether anyone is opening selectively at all. In most practices one or two people are and everybody else clicks straight through the dialog.
- Name worksets so a person can tell at a glance what to leave closed
- Set the default open state on the central file, so the dialog does the deciding
- When a machine is "slow", ask what was open before costing a hardware upgrade
The ten-minute version
Once a month, for each live project: note the central file size and compare it with last month, open the warnings list and note the count, then open the model with everything closed and time it.
Three numbers in a spreadsheet. Six months of them will tell you more about a project's health than any amount of guessing and they make the case for a hardware or workflow change far better than a shared feeling that things have got sticky.
Where this stops being a modelling problem
A well-kept model on the wrong infrastructure is still slow. If the central file sits on a server reached across a VPN, if local files are quietly redirected into a synced cloud folder, if the workstation has plenty of cores but not enough memory for the model as it now stands, no amount of purging will fix it.
That is the real value of the three numbers. They separate the two problems. A clean model that is still slow is not a modelling problem at all and at that point it is ours to solve rather than yours.
What is the warning count on your busiest project right now? If nobody in the room knows, that is the answer. We look after Revit and BIM environments, CAD workstations and the everyday IT support London architecture practices run on. If the numbers above are going the wrong way, tell us what they say.
