Fixing first layer problems

Most brick-print failures start in the first layer. Get it smooth and bonded and the rest follows.

What you will see

Gaps between the lines of the first layer
Pieces drag or get knocked off mid-print
Squashed, bulging bottom edges

What to try, in order

Slow the first layer to about 25 mm/s.
Clean the plate with warm water and dish soap, and do not touch it afterwards.
Bed: textured PEI at about 55 to 60 °C for PLA, 70 to 80 °C for PETG.
Re-run your printer’s bed levelling and Z offset check.
PETG: bed at 75 to 80 °C for the first layer.
Add a 3 to 5 mm brim for small pieces.

Change one thing at a time and test with one piece, not a whole plate.

Good to know

Too close to the plate gives bulging edges (see too tight); too far gives gaps.
Parts still lifting later? See warping.

Where we give numbers, they come from our own tests on a Bambu P1S with a 0.4 mm nozzle plus advice from other makers, and other printers need small adjustments. Our print settings page has the full table. Printed bricks are not toys: small parts, a choking hazard, not for children under 3.