How to Quote a Tiling Job: Area, Waste and Prep Lines Checked With AI

Quote a tiling job in five blocks: net area per surface from measured sizes, waste set by layout and tile size, adhesive and grout from the data sheet's coverage, waterproofing and prep on their own lines, and labour by tile size. Then have an AI assistant recompute each line as a second check, never as the first calculator.

Most errors on a bathroom quote are not in the tile price. They hide in a door deduction that was never made, an adhesive count read from the wrong end of a coverage range, or a waterproofing line nobody wrote. An assistant catches some of these and misses others, and the bathroom worked through here shows which is which. Every measurement, price and hour below is an illustrative round number chosen to show the arithmetic, so swap in your own.

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Measure each surface on its own, then deduct the openings

A single figure such as "bathroom, 15 square metres" is where most quoting errors begin, because the floor, the shower walls and the half-height walls need different tiles, different waste and different labour. Record each surface separately, with the unit written beside every number.

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The example bathroom has a 2.4 m by 1.8 m floor (about 7 ft 10 in by 5 ft 11 in) and a 2.4 m ceiling. A walk-in shower, 1.2 m by 0.9 m, fills one corner. Its two tiled walls run to 2.1 m and hold a niche 0.3 m wide, 0.6 m tall and 0.1 m deep. The remaining walls are tiled to 1.2 m, and the door is 0.8 m wide.

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The niche is the line most often forgotten. Its back adds 0.18 m², its two sides 0.12 m² and its top and bottom 0.06 m², so the reveals total 0.36 m². You deduct the 0.18 m² opening from the wall because the back of the niche replaces it, which leaves a net gain of 0.18 m² of tile. If you price in square feet, convert once at the end: 15.51 m² is about 167 ft².

Write the working next to each result, exactly as in the table. A check, whether by a colleague or an assistant, can only follow numbers that show where they came from.

Waste is a layout decision, not a flat 10%

Waste covers the offcuts that cannot be reused, the tiles that break, and the spare you need for the odd bad cut. It rises as the layout needs more angled or small cuts. Retailer and installer guides tend to start at about 10% for a straight lay and about 15% for a diagonal lay, put herringbone higher (figures from 15% to 25% appear), and disagree about large formats: 10% to 15% is common, but suggestions run from 8% to 20%. None of these is a standard. Treat them as starting points and replace them with your own record.

Apply the allowance to the net area first, then round up to whole boxes or sheets. On the example floor, 3.24 m² plus 10% is 3.56 m², which is 2.48 boxes of 1.44 m², so you order three boxes (4.32 m²). The mosaic area of 1.08 m² plus 15% is 1.24 m², or 13.8 sheets of 0.09 m², so you order 14. The walls, 11.19 m² plus 10%, need 12.31 m² or 8.55 boxes, so nine boxes (12.96 m²).

Notice what the rounding does. Three floor boxes leave 1.08 m² over the net area, a third more than the job needs. That surplus is your spare stock for the customer, so label one box with the batch number and leave it behind. Order every box for the job at once as well, because a later order can come from a different batch with a visibly different shade.

To tighten the percentages, log net area, area ordered and area left over on every job. After ten jobs, paste the log into an assistant and ask for the average leftover by layout. That is a sensible use of AI because the sums are simple and you can confirm the answer with an average in a spreadsheet.

Adhesive and grout: take coverage from the data sheet

Adhesive coverage depends on the trowel notch, the tile back and the substrate, so no single figure is safe. The data sheet for one large-format mortar publishes a coverage range per 22.68 kg (50 lb) bag for each notch: 8.4 to 9.3 m² with a 6 mm square notch, 5.6 to 6.2 m² with a 6 × 9.5 mm notch, and 3.5 to 4.4 m² with a 19 × 14 mm U-notch at 30 degrees. The same sheet asks for at least 95% contact under the tile in wet areas and at least 80% in dry ones, and says larger tiles may need back-troweling to reach it. You can see the table on the maker's product page; your own adhesive will have its own numbers.

Use the low end of each range, because the high end assumes a perfect bed. For the example bathroom the sums run surface by surface:

• Main floor: 3.24 m² at 3.5 m² a bag is 0.93 bags.
• Shower floor mosaic: 1.08 m² at 8.4 m² a bag is 0.13 bags.
• Shower walls: 4.59 m² at 5.6 m² a bag is 0.82 bags.
• Half-height walls: 6.60 m² at 5.6 m² a bag is 1.18 bags.

The total is 3.05 bags, so the order is four. Rounding down to three leaves you 0.05 of a bag short on a wet-area job and a trip to the merchant mid-tile. Rounding each surface up separately would give five bags, which over-orders. Add the fractions, then round once.

Grout is geometry. For one square metre of tiling, the joint volume in litres is the joint width times the tile thickness times (length plus width) divided by (length times width), with every dimension in millimetres. Multiply by the grout's density in kilograms per litre, which the data sheet states or builds into its consumption formula. This example uses 1.6, so swap in the figure for your own grout. Three tile types from the same bathroom show how far the figures spread:

On the whole bathroom that gives 11.19 × 0.16 + 3.24 × 0.16 + 1.08 × 0.77, which is 3.14 kg. The geometry is a floor, not a forecast, because some grout always ends up on the sponge and in the bucket. I add 25% as my own allowance, which gives 3.9 kg and a single 5 kg bag. Grout makers also print consumption tables or formulas on their data sheets. If the table for your grout gives a larger figure than the geometry, buy to the table.

Waterproofing lines that thin quotes leave out

A membrane in a shower is a set of parts, not one line. The page for one sheet membrane lists the membrane itself (overlapped by 5 cm, or butted and covered with a sealing band), pre-formed inside and outside corners, seals for pipes that pass through it, and a drain with a bonding flange. It also says to wait 24 hours before water testing and before setting tile over it, using the thin-sets it names. That wait belongs in your programme even though it takes no labour. A liquid-applied membrane has its own coats, thickness and cure times on its data sheet, and the same rule applies: read it, and price what it says.

The extent of waterproofing, such as how far up the walls and whether the whole floor is covered, comes from the rules that apply to your type of building and from the membrane maker's instructions. An assistant cannot know either, so write the extent down yourself. In the example the membrane covers the whole floor and the shower walls to full height:

• Membrane: 4.32 m² floor plus 4.41 m² shower walls is 8.73 m². With 10% for overlaps and trimming it is 9.6 m², bought as a 10 m² length.
• Sealing band: 2.1 m where the shower walls meet the shower floor, 2.1 m up the shower's vertical corner, and 5.5 m round the other floor edges, which is 9.7 m. With 10% added it is about 11 m.
• Four pre-formed corners, two pipe seals (valve and shower head) and one drain with flange.
• Five hours of labour, plus the 24-hour wait before the water test.

These lines cost about $296 in materials in the example. They are exactly the lines a rushed quote drops, and a customer who sees them listed understands why your price sits above a one-line "supply and fit" figure. For the scope wording around them, see the bathroom estimate template that catches missing lines.

Prep lines: strip-out, levelling and backer board

Prep is where jobs go over budget, because you price it before you can see the substrate. List it in three parts so each can be adjusted on its own: strip-out and disposal, substrate repair and levelling, and backer board on wet walls.

The example allows six hours to remove the old floor and wall tiles and bag the waste, three hours to prime and level the floor, and four hours to fit six sheets of backer board to the shower walls (4.41 m² of wall plus 15% for cuts is 5.07 m², and each board covers 0.96 m², so six boards). Materials for those lines come to $60 for disposal and $189 for board, screws, tape, levelling compound and primer.

The unknown is the floor. Suppose the strip-out reveals a fall of 14 mm across the 2.4 m length. Your draft allowed for one 25 kg bag of levelling compound at an average depth of 3 mm. A linear fall of 14 mm averages 7 mm when you level to the high point, which is 2.3 times as much compound, so three bags, plus about two more hours for the second pour and the wait between layers. That is an extra cost the customer never saw coming unless the quote said so. Write the allowance as a provisional sum:

Levelling: allowance of one 25 kg bag (3 mm average depth). If the
substrate needs more, extra compound is charged at cost plus handling
and extra labour at the hourly rate, agreed with you before we continue.

The tile installation contract tutorial covers substrate acceptance and warranty clauses in more depth, and it is worth reading before you finalise this wording with an adviser.

Labour by tile size: build the rate from your own timesheets

Hours per square metre do not fall steadily as tiles get bigger. Mosaics are slow because there are so many pieces and so many cuts. Very large tiles are slow because they need two people, a flatter substrate and careful control of lippage (one tile edge sitting proud of its neighbour). The quick part of the curve sits in the middle. The figures below are made-up round numbers to show the shape, in person-hours per net square metre for setting, grouting and cleaning:

Your own rates come from your timesheets. After each job, divide the hours booked to tile setting by the net area and keep the result by format. Within five or six jobs you will have numbers that beat any table, including this one.

For the example bathroom, tile setting takes 11.19 × 1.0 for the walls, 3.24 × 0.9 for the floor and 1.08 × 3.0 for the mosaic, which is 11.2 + 2.9 + 3.2 = 17.3 hours. Add 18 hours of prep and waterproofing and the job is 35.3 person-hours. With the cure and levelling waits, a two-person crew would plan five working days elapsed.

Putting the lines together, with materials at cost plus 10% handling and labour at an illustrative charge-out rate of $60 an hour:

Materials with 10% handling are $1,603. Labour at 35.3 hours and $60 is $2,118. The quote comes to $3,721 before any provisional sums.

Hand the draft to an assistant as a second pair of eyes

With the quote built, give an assistant the same inputs and a narrow job: recompute, do not rewrite. The version below uses a first draft that contains deliberate mistakes, which is how drafts look when written at the end of a long day. The prompt also fixes the rules, so the assistant cannot quietly pick a different waste percentage.

You are checking a draft tiling quote. Do not rewrite it and do not
change any total. Work only from the inputs below. Show your working
for every recomputed figure, round purchase quantities UP to whole
boxes or bags, and write "cannot check" if an input is missing.

ROOM: floor 2.4 m x 1.8 m, ceiling 2.4 m. Walk-in shower 1.2 m x 0.9 m
in one corner, tiled to 2.1 m, niche 0.3 x 0.6 x 0.1 m. Door 0.8 m
wide. Other walls tiled to 1.2 m.
MY RULES: waste 10% straight lay, 15% mosaic. Box 1.44 m2, mosaic
sheet 0.09 m2. Adhesive coverage per 22.68 kg bag, use the LOW end:
floor 3.5-4.4 m2, mosaic 8.4-9.3, walls 5.6-6.2. Grout density
1.6 kg/l, plus 25%. Wall 10 mm thick 2 mm joint, floor 10 mm 3 mm
joint, mosaic 50 x 50 x 6 mm 2 mm joint. Labour hours per m2: wall
1.0, floor 0.9, mosaic 3.0.
DRAFT LINES:
1. Floor 600x600: net 3.24 m2, waste 10%, 3 boxes
2. Shower floor mosaic: net 1.08 m2, waste 15%, 14 sheets
3. Wall 300x600: net 12.15 m2, waste 10%, 10 boxes
4. Adhesive: 3 bags
5. Grout: 0.16 kg/m2 on all areas plus 25%, one 5 kg bag
6. Waterproofing: sheet membrane 10 m2
7. Labour: wall 1.0 h/m2, floor 0.9, mosaic 1.0, prep 18 h
TASK: (a) recompute lines 1-5 and 7 using the net areas as given;
(b) list lines a bathroom tiling quote normally has that this draft
lacks; (c) list anything you could not check.

A typical reply (illustrative) looks like this, and the comments after it are what I would do with each point:

1. Floor: 3.24 x 1.10 = 3.564 m2 = 2.48 boxes, so 3. Agrees.
2. Mosaic: 1.08 x 1.15 = 1.242 m2 = 13.8 sheets, so 14. Agrees.
3. Walls: 12.15 x 1.10 = 13.365 m2 = 9.28 boxes, so 10. Agrees.
4. Adhesive at low end: floor 0.93 + mosaic 0.13 + walls 2.17 =
   3.23 bags, so 4. Draft says 3: short by one bag.
5. Grout: mosaic needs 2 x 6 x 100 / 2,500 = 0.48 l/m2 = 0.77 kg/m2,
   not 0.16. Total 3.29 kg plus 25% = 4.11 kg. Still one 5 kg bag.
7. Labour: mosaic at 1.0 h/m2 conflicts with your rule of 3.0.
   Mosaic hours should be 3.24, not 1.08. Total tile hours 18.3.
(b) Missing: sealing band, pre-formed corners, pipe seals, drain,
    backer board, levelling compound, trim, silicone, spacers,
    disposal, floor protection, parking or access, cure wait.
(c) Could not check: waterproofing extent, prep hours.
Note: 10% waste on 600 x 600 floor tile is below the standard 15%.

Four of those points are right and worth acting on: the adhesive count, the grout rate on the mosaic, the mosaic labour rate and the list of missing lines. I would add all of them to the quote. The grout point changes nothing about the order (still one bag) but tightens the headroom in the bag from 1.7 kg to 0.9 kg, so it would bite on a bigger job. The last line is an opinion dressed as a standard. The waste guides quoted earlier disagree with each other, none of them is a standard, and my rule says 10% for a straight lay. It still prompts a quick look back at my last three floor jobs to see what I actually threw away.

The check also missed something. The draft's wall area of 12.15 m² is wrong, and the reply accepted it because the task said to use net areas as given. A second pass catches it:

Now recompute each net area from the ROOM block and list differences.

The reply (illustrative) works out the half-height walls as (8.4 - 2.1 - 0.8) × 1.2 = 6.60 m², giving 11.19 m² of wall rather than 12.15 m². The draft had used 6.3 m of wall and forgotten the door. At 11.19 m² the waste-adjusted need is 8.55 boxes, so the order falls from ten boxes to nine. The lesson is that an assistant checks what you ask it to check. If you want areas re-derived, ask for it, and put the door in the prompt.

Some rules make this routine reliable:

• Give it your inputs and your rules, not the finished quote alone.
• Tell it to show working, and re-run anything it flags in a spreadsheet. Treat any sum an assistant does in its head as unchecked.
• Tell it which way to round, since it will otherwise round 3.05 bags to 3.
• Forbid it from changing totals, so differences stay visible.
• Keep customer names and addresses out. The check needs dimensions, quantities and rates only.
• Do not let it measure from photos. The vendor's own image documentation says counts can be imprecise and location outputs approximate, and asks users to verify them.

The same approach works for flooring, and the flooring quote template applies it to underlay and thresholds.

Quote wording: one vague line against eight clear ones

Before: "Bathroom tiling, supply and fit, $4,100." The customer cannot tell what is inside it, and neither can you in six weeks when the substrate turns out to be uneven.

After, each as its own line: strip-out and disposal; levelling to an agreed allowance; backer board to shower walls; waterproofing with membrane, bands, corners, seals and drain; wall tile 300 × 600 supplied and fitted, 11.19 m² net; floor tile 600 × 600, 3.24 m² net; shower floor mosaic, 1.08 m² net; adhesive, grout, trim and sealant. Then the exclusions: plumbing and electrical work, removal of fixtures, substrate repair beyond the allowance, and shade variation between batches.

Decide whether the document is a quote or an estimate before it leaves, because they commit you differently. The comparison of quotes and estimates for trades sets out the difference. Then give the price an end date, because tile and adhesive prices move; the quote validity tutorial explains how to set one.

Three smaller jobs and one that went wrong

A diagonal hallway. A floor of 8.4 m² in 600 × 600 tiles laid diagonally at 15% needs 9.66 m², which is 6.71 boxes, so seven boxes (10.08 m²). The same hallway laid straight at 10% needs 9.24 m², or 6.4 boxes, which also means seven boxes. The diagonal costs you more cutting time, not more boxes, so the labour line is where it shows.

A kitchen splashback. A run of 3.6 m by 0.6 m is 2.16 m². With 75 × 150 mm tiles, 7 mm thick, in a 2 mm joint, the grout geometry is 2 × 7 × 225 ÷ 11,250 = 0.28 l/m², or 0.45 kg/m². That is 0.97 kg for the splashback and about 1.2 kg with the 25% allowance, so buy the smallest bag. Boxes of 0.5 m² mean 2.16 plus 10% (2.38 m²) rounds to five boxes, so rounding waste stays small.

A floor of 600 × 1,200 tiles. The sources suggest 10% to 15% for large format, so the rate depends on how many cuts the room forces. Count them on the plan before choosing: a room with three alcoves needs the top of the range, a plain rectangle the bottom.

The customer-supplied tiles. A customer buys tiles from a clearance shop, net area plus 5%, and two boxes arrive damaged. The shop's remaining stock is a different batch. The finished wall shows a shade change at the niche, and the customer blames the tiler. A quote line reading "tile supplied by customer: quantity and condition are the customer's responsibility; recommended order is net area plus 12%; shade variation between batches is not covered" would have started a different conversation. Ask for a photo of the box labels before you start.

Eight checks before the quote leaves your phone

1. Every surface has its own net area, with the door, windows and niche accounted for.
2. Each surface has a waste percentage that matches its layout, and boxes are rounded up once.
3. Adhesive uses the low end of the data sheet's range for the notch you will use, and the bag count is rounded up once.
4. Grout uses the geometry or the data sheet's table, whichever is larger, plus your allowance.
5. Waterproofing lists membrane, bands, corners, seals and drain, with the cure wait in the programme.
6. Levelling is an allowance with a provisional-sum clause, not a promise.
7. Labour comes from your timesheets by tile size, with the mosaic and large-format lines separate.
8. An assistant has recomputed the lines from your inputs, you have re-run what it flagged, and the exclusions and end date are on the page.

If you would rather map your own measuring and pricing steps with someone, that is what my AI implementation consultation covers.

Tiling quote questions that come up after the first one

Should I quote tiling per square metre or as a fixed price?

Per-square-metre rates suit plain floors and simple walls. A bathroom with a niche, waterproofing, a drain and unknown substrate is better quoted as a fixed price built from visible lines, with the per-square-metre figure kept only as a sanity check. Customers compare fixed prices more easily, and the lines show what is and is not included.

Can AI measure a room from a photo?

Not reliably. Anthropic's own image documentation says Claude's location outputs are approximate and its counts of objects in an image can be imprecise. Measure with a tape or laser measure, type the numbers in, and let the assistant recompute from those typed figures. Use the photo only to remind you what the room looked like.

How much spare tile should the customer keep?

Leave at least one unopened box from the same batch, labelled with the batch number, for future repairs. Keep that separate from your waste allowance, which covers cuts and breakages during the job. Boxes sold in whole units usually leave some spare anyway, and on the example floor whole-box rounding alone leaves 1.08 m² over the net area, about a third more than the job needs.

What if the customer supplies the tiles?

Quote labour, adhesive, grout and sundries only, and write the tile quantity down as the customer's responsibility, with a recommended order that includes your waste allowance. Add that shade variation between batches and damage before delivery are not covered. Ask for a photo of the box labels so the batch number is on file.

Which AI assistant is best for checking a quote?

Any of the main assistants can recompute a quote if you give it your inputs and rules. Method matters more than brand: show working, round purchase quantities up, never let it change totals. Leave customer names and addresses out of the prompt, since the check only needs dimensions, quantities and rates.

Further reads

• Bathroom Renovation Scope of Work: Draft Room-by-Room Lines With AI — Write the room-by-room scope that sits above these quote lines.
• Renovation Quote Template: Room-by-Room Scope Written With AI — Scale this bathroom layout up to a whole-house quote.
• AI Estimating Software for Flooring: Test Accuracy on Your Own Plans — See whether estimating software beats your own takeoff.
• Turning On-Site Voice Notes Into Job Sheets and Quotes With AI — Capture site measurements by voice instead of in a notebook.
• How to Quote Scaffolding: Elevations, Boards and Hire Periods With AI — A worked wrap-around quote: elevation areas, lifts, boards, erect and dismantle labour, weekly hire and extras, with an AI check that the sum reconciles.
• AI Tools and AI Development: The Complete 2026 Guide — the AI hub, including every tutorial in the AI-for-business series.

Sources: Custom Building Products' VersaBond-LFT product page (coverage per 50 lb bag by notch, minimum mortar contact, back-troweling), Schluter's KERDI product page (2 in / 5 cm seam overlap or KERDI-BAND, pre-formed corners, pipe seals, bonding-flange drain, 24-hour wait before testing), grout data sheets (consumption formula, density), retailer and installer waste-allowance guides, and Anthropic's vision documentation (limitations section).