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What updates when the design changes
The tiles in model space drive the sheets. Move, resize or rotate a tile, or let the alignment move under it, then press Update Sheets: the layouts, viewports, match lines, key maps and sheet set follow, and tiles that did not change are skipped. Nothing is rebuilt. This page says what happens for each kind of change, what stays yours, and where the limits are; each section links to the page that documents the buttons.
What happens when a tile moves
Move or resize a tile polyline in model space, then press Update Sheets. The change is detected, the layout for that tile is updated, and its match lines and key maps with it; tiles that did not change are skipped.
Rotate a tile and the sheet follows: the viewport view, the north arrow and the match lines re-orient, through a full 360 degrees, in every mode, on built and adopted drawings alike. Rotate the model-space tile, not the paper-space viewport. The tile drives the result.
Build Sheets stays greyed out once sheets exist, on purpose: Build is first-time only. Rebuild Sheets regenerates from scratch, for a set that has gone badly out of sync. Retile, in the Health panel, regenerates the tile layout itself when the underlying geometry has changed. The rule that covers most days: build once, then Update Sheets.
In one firm's eight-week evaluation, 273 layouts were updated this way alongside 498 built. That is the revision work the set absorbed rather than the drafter.
What happens when the alignment moves
Tiles are placed against the alignment at preview. If the alignment geometry is edited afterwards, Health raises a drift warning, tracked per alignment.
Step 1. Open Health and press Update Tiles. The tile positions are updated to the new geometry. The button only appears while the warning is active.
Step 2. Press Update Sheets on your workflow tab so the layouts follow. Only the changed tiles are updated.
Step 3. Press Refresh on Health to confirm the warning has cleared.
If you edited the viewports on purpose and want those edits kept, use Normalize VP rather than Update Tiles. A different warning, that tiles were modified since preview, means the tiles were moved rather than the alignment: press Retile on Health, then Update Sheets.
In alignment placement the station range each tile covers changes with curvature, fewer stations through a curve and more along a straight, so the alignment stays inside the viewport on every sheet. That is expected, not drift.
Which sheet elements update
On every changed sheet, Update Sheets refreshes the viewport and its view; the match lines and their labels, with the references to neighbouring sheets; the key map viewport, with the current sheet's tile highlighted; the north arrow, scale bar and title block attributes configured on _TEMPLATE_TB; and, once you press Sync SSM, the sheet set entries.
Edits to _TEMPLATE_TB flow the same way. Move the north arrow, scale bar or key map label on the template, or redefine a support viewport, then press Update Sheets: the new positions reach every built sheet. Until you do, Health shows a template drift warning.
Items configured after the build are backfilled. Configure the north arrow, scale bar, attributes, match lines or key maps on _TEMPLATE_TB, press Update Sheets, and they are added to every existing sheet. That pass is add-only: it places what is missing and leaves your sheet content alone.
A referenced file that changed since the build, the title block XREF included, raises the stale-reference indicator rather than letting sheets plot quietly from an outdated reference. Reload it, press Update Sheets, and if the title block itself changed, press Set TB again.
What you control and what SheetAgent maintains
Only what SheetAgent for Civil 3D created is maintained: the sheet, viewport, match line and key map layers it generates, the support blocks it places, the attributes it fills, and the sheet set entries. Their colour, plot and lock state are set on build and on update.
Your own layers are left alone, with their colours, linetypes and plot styles. Your own per-sheet edits, anything other than the managed decorations, are not overwritten by an update. The one exception is viewport freeze and thaw states, which an update can reset; to set those deliberately, set the layer state on one viewport and copy it across the sheets with Apply Layers.
Viewports you edited by hand are a choice, not a fight. When a viewport has been moved, resized or rescaled, Health offers Normalize VP and asks which side should win. Viewports, the default, snaps the edited viewports back to what the program set. Model tiles adjusts the model-space tiles to match your edits, which become the new baseline. Once normalized, Update Sheets works from that baseline and the viewports stop snapping back.
Can I change the viewport size or scale after the sheets are built?
Viewport size: yes, at any time. The maximum viewport area is defined once on _TEMPLATE_TB, with Primary VP on the Single VP tab or Set Viewport Size on Multi VP and PDF/Detail. Redefine it, and Health shows a size drift warning with a Retile button. Press Retile, review the reported tile changes, and answer Yes to update the layouts, or run Update Sheets afterwards. Sheets are added or removed so the coverage stays intact: removed tiles delete their layouts and new tiles create them. Update or Build alone will not re-cut the sheets to a new size.
One sheet: yes. Shrink a tile in model space and only that layout reflects it. Or resize the viewport inside a layout and choose Model tiles in Normalize VP, and the tile updates to match.
Spacing on plan and profile sheets: yes, through Layout Adjustment, for the gap between the plan and profile viewports and the bottom margin, on stacked arrangements only. It does not change viewport size or scale.
Scale is decided at preview. It is set in the Sheet Naming dialog, and changing your mind means running the preview again. Changing the scale of a set is not common in civil work. What is common is a blow-up of a critical area at a smaller scale, and that is an added tile: press Add Tile, place it at the scale you want, and press Update Sheets. Sheets are grouped by scale when they are numbered.
Coverage gaps after a change
After a tile moves or an alignment shifts, coverage can fall short somewhere.
Step 1. Open Health and press Gap Preview. Non-plotting markers appear in model space wherever tile coverage falls below your minimum.
Step 2. Press Add Tile. It is gap-fill aware, so it covers gaps at the start, at the end and in the middle, and it can add tiles at a different scale or naming.
Step 3. Place or accept the new tiles over the highlighted areas.
Step 4. Press Update Sheets, not Build Sheets. Layouts are generated for the new tiles and unchanged tiles are skipped. Press Gap Preview again to turn the markers off.
Sheet Set Manager after an update
After Update Sheets, Renumber Sheets or Edit Sheet Names, press Sync SSM in the sheet management section. Review the analysis, which lists what is in sync and what will be added, updated or removed, then confirm; the sheet set entries are changed so the file matches the drawing. A sheet set edited outside SheetAgent for Civil 3D is reconciled the same way.
Renumbering cascades to key maps, labels and sheet set entries, and every sync rewrites the page number and total sheet fields from the current sheet order, so a count such as 1 of 30 stays right as sheets are added or removed.
Sync SSM only becomes available once the drawing is linked to a sheet set; if it is greyed out, press Sheet Set Manager first. If a sync reports that it cannot lock the sheet set, close the Sheet Set Manager panel in Civil 3D and try again.
On a Project Control project
Every change starts in the control drawing. Change the tiling there: retile, move or delete tiles, or retype a sheet number. Run Assign Disciplines if the numbering needs re-approving, then Build Set or Update, and every discipline follows the new state.
Retile, Set TB, Primary VP, Renumber and sheet names in a discipline drawing defer to the control drawing and point you back there. Re-cutting tiles locally would disconnect that file from the project. Everything else on those sheets is yours, and project updates never touch what you added.
Two rules keep a project stable through change. Sheets renumber but files never rename, so file names and the links into them stay put. A deleted sheet is removed rather than held open as a numbered gap. If every sheet in a file is removed, that drawing retires to the backup folder you nominated. Nothing is deleted.
The limits, stated plainly
Build once, then Update. Build greys out by design after the first build, and Rebuild is for a set that has gone badly out of sync; it regenerates from scratch.
Layout Adjustment changes spacing on stacked plan and profile sheets only. On side-by-side sheets it refuses, and a sizing change there goes through Retile.
Scale is a preview decision, not an update. A tile at a new scale is an added tile.
PDF import builds detail sheets from PDF pages. It is not a way to bring in plan drawings.
Match lines drawn in paper space are approximate, and Health says so; model space is the accurate choice, and it is the only one in path and alignment placement.
A vertical profile split that runs out of height reports the segment as OVER rather than changing the scale for you.
Something here not matching what you see? Tell us and we will fix it. Back to Resources, or the FAQ.