Uploading and calibrating your plan

The plan take-off starts here: attach the plan set, choose a page, crop the area you want to measure, and calibrate the scale. The single most important step is calibration. Get it right and every area you trace is right.

Attach the plan

On the H1 Compliance page, under Plan PDF (optional), attach the architectural plan set. The upload goes straight to secure storage against your account. Once attached, the file shows its size and attach date with View plan, Download, Replace and Remove.

Replacing the plan with a new issue keeps your work. Every drawn take-off diagram is carried over live - the crop, traced geometry, linked areas and scale calibration all keep working over the replacement PDF - and the plan card shows a dismissible warning asking you to check the carried-over take-offs against the new issue.

The plan is optional - you can enter areas without one - but attaching it unlocks the take-off, the marked-up report diagrams, and the insulation take-off.

Open and navigate

Multi-page sets open in the plan viewer. Move between pages with the page controls or Page Up / Page Down and the arrow keys. Zoom with the mouse wheel or the zoom control (50% to 300%). Rotate a sideways page 90° either way.

Thermly indexes the pages when you upload, tagging them (cover, floor plan, roof plan, elevation, window / door schedule, insulation spec, and so on) so you can jump straight to the page you need. A scanned set, with no text layer to read, is indexed too: its pages are classified and their written content transcribed, so the page tags and the plan-reading features work on it as well. That analysis runs once per uploaded plan, and a large or scanned set can take a few minutes; the plan card says so while it works.

Reference the plan while you work

View plan on the plan card, or Plan in the report bar at the foot of the page, opens a floating, draggable, resizable plan window that stays open over the form, so you can read the drawing while you enter values. Right- or middle-drag to pan; wheel to zoom.

The AI plan summary

An ✨ AI plan summary button appears on the plan card once a PDF is attached (and again, as AI Summary, in the report bar at the foot of the page). AI features are on for every account by default, within a fair-use allowance; if an administrator has switched them off for your account, or the allowance is used up, the button is disabled and its tooltip says why. It opens a floating window - like the plan viewer - listing everything the drawing set states that helps complete the form: project information, roof and ceiling insulation and skylights, wall constructions with the window and door schedule, slab and other floors, and any H1 notes. Sections follow the form top to bottom, and every item cites the plan page it was read from, so you can use it as entry hints and to double-check values.

The wall section ends with the plan's window & door schedule as an ordered table - one row per unit in tag order (W1, W2 … W10, then doors, then garage doors), with the overall W × H in millimetres, the unit's own description where the plan prints one, and the page it was read from; skylights get the same table under the roof section. Sizes come from the plan's own schedule sheet as read when the plan was uploaded (the same lookup the plan mark-up uses to size an opening from its number) or, on a set with no schedule sheet, from the sizes marked beside each unit on the drawings themselves, with the AI's reading of the plan text filling in descriptions and any unit the schedule did not size - the line under the table says which is which, and rows marked ✱ are AI-only.

The read runs once per plan in the background with a live progress ticker - closing the window (or the tab) does not stop it. The finished summary is saved with the project and reloads instantly; it only regenerates when the plan PDF is replaced (or, once, when the summary format itself has been upgraded since it was generated - a short re-read the next time you open it). Like everything AI-derived, it is a reading of the drawings for you to verify, not an input to the calculation.

Want to see one before attaching a plan of your own? The built-in sample projects ship with their plan summary (and AI Review) pre-computed, so every account can view both in full - no AI runs, nothing is charged.

Crop the area to mark up

Drag on the page to select the region you want to take off (for example, one floor plan), then continue to mark-up. Cropping keeps the canvas focused on the elements you are measuring. You can change a diagram's crop later without losing anything: the drawing - shapes, cut-outs, calibration and legend - is re-anchored onto the new rectangle, so measured lengths stay exactly what you typed.

Re-calibration is not optional

Calibration ties on-screen distance to real-world distance. Without it, areas are meaningless.

To calibrate: click Scale (next to the drawing tools), click two points on a known dimension (a dimensioned wall, a grid spacing, a scale bar), and enter the real distance in millimetres or metres. From then on, every length and area you draw on that page is measured against that scale.

Why "re-calibration" matters. To save you time, a new diagram can inherit the scale from another page of the same plan. That is a convenience, not a guarantee. Different sheets are often plotted at different scales (a 1:100 floor plan, a 1:50 detail), and a plan printed "not to scale" or scaled to fit a page defeats an inherited scale entirely. Inherited areas can be silently wrong.

Thermly makes the scale's origin visible on the scale chip. A teal chip is a scale you calibrated yourself on this diagram; an amber chip is a scale Thermly derived or carried over, and it carries a Re-calibrate button:

Chip	Meaning
Scale 1:100 · from plan (amber)	Read from the drawing's stated ratio. Convenient, but unconfirmed - re-calibrate against a known dimension before you trust the areas.
Scale inherited from plan - re-calibrate for accurate areas (amber)	Carried over from another page. Re-calibrate before you trust the areas.
… px/mm or H … · V … px/mm (teal)	Calibrated by you on this diagram. The H·V form is a two-axis scale: horizontal and vertical calibrated separately, for a squashed or stretched plan.

The rule of thumb: calibrate the page you are about to measure, against a dimension you can read on that page. If the chip is amber, re-calibrate. It takes ten seconds, and it is the difference between a defensible take-off and a wrong one.

A diagram with no scale at all is a different case, usual on a scanned plan whose stated ratio cannot be read: what you trace has no length or area to give the form. Thermly says so on the diagram's card and on each row linked to it, with a Set the scale on the plan action that reopens the diagram. Set the scale and save, and the runs you already traced become wall rows with their lengths. See My traced walls show 0 m².

Two-axis calibration

If a plan is stretched or squashed (common with photocopied or fit-to-page PDFs), calibrate the horizontal and vertical separately with H×V scale (beside the Scale button) so both axes measure correctly.

Next

• The plan take-off - trace walls, roofs, floors, openings and skylights.