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SketchUp modelling guide

Draw it this way, and the quantities come out right

Constructio measures what the model contains. Eight simple habits make the difference between "roughly" and "right" — most of them the free SketchUp extension does or checks for you.

SketchUp extension L-shaped and curved walls
  1. 01

    One element, one closed group

    Every wall, slab, column, beam, stair, window and door is its own group, and the group is a closed solid — Entity Info says "Solid Group". Only a closed group has a volume, so concrete and blocks can be counted. The extension's check list shows open groups in red.

  2. 02

    Walls: straight, L-shaped or curved

    A wall can be straight, L-shaped, S-shaped or curved and still be one group: the thickness is read from the wall's top face, so the shape does not matter (extension 0.4.1 and later). Use separate groups when the material, thickness or exterior/interior changes.

  3. 03

    No overlaps between walls and slabs

    Start walls on top of the slab and stop them under the next slab. Where a wall runs into a slab, the same volume would be counted twice — once as wall, once as concrete.

  4. 04

    Cut openings into the wall

    Make the window and door holes in the wall group itself, then put the window or door in its own group. Wall areas and block counts are then measured with the openings deducted. Frame and glass can stay inside the window group as parts.

  5. 05

    Storeys as groups

    Put each floor's elements inside a group typed "Storey" (Ground floor, 1st floor…). Storeys are containers: the elements inside are counted one by one, floor by floor.

  6. 06

    Rooms as boxes for finishes

    Draw each room as a box from the inside wall faces up to the ceiling and type it "Room". Write the finish in the name — "Bathroom 1 - ceramic - wall 240", "Living room - parquet". Floor finish, skirting, plaster, paint and wall tiles are then measured room by room; you do not draw finish layers.

  7. 07

    Type and material with the extension

    Select a group, choose its type and material in the Constructio panel and press Apply: the IFC class and a name the site understands are written for you ("AAC block 20 exterior wall").

  8. 08

    Clean check list, then export

    Before exporting, the check list should show no unclassified or open parts. Then File → Export → 3D Model → IFC and upload the file on your project's "Quantities from IFC" page.

Frequently asked

L-shaped, S-shaped and curved walls

No. Since extension 0.4.1 an L-shaped wall drawn as one group is measured correctly — the thickness comes from the top face, not from one side. Earlier versions read a 15 cm L-shaped wall as 26 cm; if you named walls with an older version, select them and press Apply again.
SketchUp turns a curve into many small flat faces. If the wall group is a closed solid, its volume is exact and the thickness is read from the top face, so the quantities are right. More segments make the curve smoother but do not change the result noticeably.
The volume is still exact. If the top is sloped, the thickness cannot be read from a flat top face and the extension falls back to the side faces — for a straight wall that is still right. For a curved wall with a sloped top, check the thickness the panel shows and correct the name if needed.
Draw them as their own groups and do not let the wall pass through them; cut the wall where a column stands. Otherwise the same volume is counted as both wall and concrete.

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