AMeasuring for proper fit
- Set the cabinets first. Measure only after the base cabinets are level, plumb, shimmed, and screwed to the wall.
- Measure to the back wall. Run your tape from the back wall (not the front of the cabinet) — that is the most accurate dimension and accounts for any overhang.
- Measure each leg of the run. For an L or U-shape, mark the length and depth of every leg on a sketch.
- Note end conditions. For each open end, record whether it butts to a wall, an appliance, or stops free.
Overhang rules — how much extra to add to the cabinet length
| End condition | Add | Notes |
|---|---|---|
| Open & capped end | 1" overhang | Standard finished end |
| Butts to an appliance | 1/8" overhang | Refrigerator, range, dishwasher |
| Butts to a wall or cabinet | 0" overhang | No overhang at all |
Each finished applied end-cap adds 1/16" to the top length. Each butt splash (a splash that meets the end of the top) adds 13/16" to the top length.
BDetermining depth
Standard kitchen base cabinets are 24" deep front-to-back. Pick the top depth that gives you the front overhang you want.
25-1/4"
Kitchen
~1-1/4" front overhang
25-1/2"
Kitchen
~1-1/2" front overhang
22-1/2"
Vanity / bath
Standard vanity cabinet
For an island top (no wall behind it), aim for a 1-1/4" overhang on each side. If you want seating on one side, add knee-space overhang there — usually 12" to 15" beyond the cabinet front.
Bar tops are typically 12" and up depending on the seating depth you want. Mark every leg of the run on your sketch with its depth so we know whether each section is a kitchen, vanity, or bar.
CIrregular walls & the 3-4-5 method
Our post-form tops have a 3/8" scribe on the backsplash that can be sanded to fit slightly bowed or cupped walls. But before you order an L or U-shape, you need to know whether the corner is actually square — out-of-square corners need a mitre cut at a custom angle, or a template.
- Mark one wall 36" out from the inside corner.
- Mark the opposite wall 48" out from the same corner.
- Measure the diagonal between the two marks. Hold both ends of the tape exactly on the marks and pull tight — any slack will artificially lengthen the diagonal.
- If the diagonal is exactly 60" the corner is square. Off by more than 1/4" → expect to template, or order a custom-angle mitre.
3-4-5 diagram
Any 3-4-5 multiple works (e.g., 24-32-40 in tight spaces). The math is just the Pythagorean theorem applied to the corner.
DEnd treatments
On every top, mark each end as either finished (capped) or unfinished (raw):
Capped (finished)
The end is exposed (open island end, end of a peninsula, end against an appliance you can see). We apply a matching laminate end-cap so the substrate is sealed and the edge looks finished.
Raw (unfinished)
The end will be hidden by a wall or another top section in an L or U layout. We leave the substrate exposed so the next section can butt cleanly into it on site.
ECutouts: sinks, cooktops & specials
Cutouts must be specified to the centerline. Three rules cover almost every case:
- Always measure to the centerline of the cutout — and always tell us which end you measured from (left or right).
- Always specify the bowl or cooktop manufacturer, model number, and the cutout spec. The model number gives us the exact opening dimensions; never approximate.
- Never put a sink cutout on a seam. If the sink centerline lands on a planned post-form seam, the seam must be relocated. Water in a seam will eventually delaminate the substrate.
Moisture damage is not covered under warranty. Take the seam relocation rule seriously.
FDiagonal corners
A diagonal-corner top spans a 45° corner — common over revolving-tray cabinets or when a sink sits at the corner.
- Dimension A — the equal length on each leg of the corner, measured along the back wall. Both legs must match (revolving-tray cabinets are typically 36" × 36").
- Dimension B — the corner-shelf size. Always 10" smaller than dimension A.
- Dimension C — the length of the centre top at the backsplash (the triangular shelf at the top of the splash height).
- Dimension D — the cabinet front length.
- Dimension E — the overall top size (always supply this).
Sink in a diagonal corner? A 32" × 21" bowl needs a minimum 44" × 44" corner space, with a 30" sink-front cabinet cut down to 28-1/4" deep.
GU-shape, L-shape & bar tops
When a U or L kitchen has a raised bar or extended seating top, you have to add to the cabinet measurement to capture the full top length:
| Top depth | Bar size | Add to cabinet length |
|---|---|---|
| 25" | 36" bar | + 11" |
| 25" | 26" bar | + 1" |
| 25-1/4" | 36" bar | + 10-3/4" |
| 25-1/4" | 26-1/2" bar | + 1-1/4" |
Numbers assume 24" deep cabinets. Dotted lines on your sketch should always show the cabinet measurement; solid lines show the finished top dimension.
HTops over 12 feet
For runs longer than 12 feet we use a "Y" seam instead of a straight seam. The Y geometry adds strength, gives a better front-to-back pattern match, and keeps the joint out of the high-traffic sink area.
A slightly bowed wall is fine — our 3/8" backsplash scribe sands or planes to fit. Some Marion-built tops have a 5/8" scribe.
IWhen to make a template
A template is required when you have:
- An unusual shape with multiple angles or radius corners.
- A large L or U-shape that is badly out of square.
- A countertop that follows angled (non-90°) walls.
Never make a template out of paper.
Paper tears, rolls up, gets folded, and loses its sharp angles in shipping. Use heavy corrugated cardboard.
Template the cabinets — not the countertop
Build a full-size template of the actual cabinet run, then send a separate dimensioned drawing of the countertop and write "SEE TEMPLATE" on the drawing. On the template itself, mark:
- Overall dimensions on each section.
- Amount of overhang desired at every open end.
- Centerline location of every cutout.
- Splits — any template larger than 8' × 6' should be split in the middle of one wall, with the joint marked exactly as it would be assembled.
- Your account name, PO number, and customer name on the template.
Corner / angle templates
- Lay cardboard at least 72" along each wall, making sure both pieces meet in a clean, well-defined angle at the corner.
- Send a separate, fully-dimensioned drawing marked "SEE TEMPLATE".
- Mark the template with your account name, PO number, and customer name.
Cabinet-end overhang
1/4" – 1"
Butts an appliance
0 – 1/8"
Butts a wall
0"
Got your numbers?
Plug them into the 3D Builder to see your top in real time and get a shipped price.
This guide gives general recommendations only. It serves as a guide to good practice and does not constitute a warranty or representation of fitness for any particular project. Verify all measurements on site, refer to your specific cabinet and appliance manufacturer documentation, and follow all applicable local codes. We are not liable for measurements taken by the customer or installer.