Stacked floors
Stairs, shafts, risers, columns, and wet rooms that must line up from one floor to the next.
Drawing overlay
See both drawings in one frame
When a finding depends on two drawings lining up, we lay one over the other at the spot in question. You see the conflict directly instead of flipping between sheets.
From a real project review
A grease duct riser, first floor over second
The 42x8 grease duct is black because both floors draw it in the same place. The access panel is blue: it is on the first floor only. On the second floor, where the duct runs beside a hotel suite, there is no cleaning access. Open the image to inspect it.
When an overlay helps
Problems that only show when drawings line up
An overlay comes with a finding when the alignment is what shows the problem. Findings that a quote on one sheet already proves do not need one.
Architecture against structure or MEP
Equipment, platforms, and openings against the framing or services under them, or a floor plan against its reflected ceiling plan.
One area, two consultants
The same room drawn by two disciplines, when the tags or labels disagree.
How it works
Aligned on fixed features, checked before you see it
Match fixed features
We pick at least three features that appear on both drawings, such as grid intersections, columns, and building corners. The disputed element is never one of them.
Fit and check
Only scale, rotation, and position change, so a drawing at a different scale or in another file still lines up. A separate feature tests the fit; if any point misses by more than about 1/24 inch on the sheet, the overlay is not shown.
Draw from the original PDFs
Both drawings come straight from the PDF pages in your browser. Switch between both views or one at a time, and between the cited area and the full sheet.
From the waterfront hotel review
Three findings an overlay settled
These potential issues come from a published review of a 156-page hotel and restaurant set. Each one depends on two drawings of the same place lining up.
Mechanical roof plan over roof framing plan
An exhaust fan platform with nothing under it
The kitchen exhaust fan platform lands in a bay where the framing plan shows only existing rafters. No support or attachment is drawn under it.
First floor over second floor
A grease riser with no access on one floor
The grease duct riser is drawn in the same place on both floors. The access panel appears only on the first floor, and the second floor has none.
Architectural plan over mechanical plan
One room, two names
The room labeled "walk-in freezer" on the mechanical plan is the same room, kegs included, as the "walk-in cooler" on the architectural plan.
What it does not do
A shared frame, not a verdict
An overlay shows where two drawings agree and where they do not. It does not decide which drawing is right. The responsible designer confirms which one governs and corrects the other, and the finding keeps its drawing and code references for that decision.
Overlays sit inside the same whole-set review that links callouts, schedules, and code sections across sheets. For conflicts between disciplines, see cross-discipline coordination review.
Questions, answered
FAQs
What is a drawing overlay?
Two drawings of the same place laid on top of each other, so you can see where they agree and where they do not. In Groundbook AI the sheet you are on is red, the overlaid drawing is blue, and lines drawn on both are black.
Do I need to line up the drawings myself?
No. When a finding depends on two drawings lining up, the overlay comes with the finding, already aligned. Open the finding and select Show overlay on its drawing reference.
How are the drawings aligned?
We match at least three fixed features that appear on both drawings, such as grid intersections, columns, and building corners, and fit only scale, rotation, and position. A separate feature checks the fit. If any point misses by more than about 1/24 inch on the sheet, we do not show the overlay.
What if the drawings are at different scales or in different files?
Both work. The fit sets the scale, and the overlaid drawing can come from another file in the same review, such as an architectural set against a mechanical set.
Is anything redrawn or traced?
No. Both drawings are drawn from the original PDF pages in your browser. Only the alignment is stored.
Does an overlay show which drawing is correct?
No. It puts both drawings in the same frame. The responsible designer decides which one governs and corrects the other.
Keep exploring
Related pages
Read the whole set
How callouts, schedules, and code sections are linked before review.
Knowledge graphCoordinate the interfaces
Follow openings, levels, and equipment across disciplines.
Cross-discipline reviewCompare two versions
What changed between milestones, with sources.
Drawing version comparisonSee your drawings in one frame
Upload the set, and findings that depend on two drawings come with an overlay.