BOQ Budget Calculator: Spreadsheet That Prevents Overruns

Q: Why 10% contingency not 5%?

Older slabs + shafts hide 79% surprises (hollow, seepage, shaft block). 5% empties week 2, 10% holds to snag. New builds 7% ok with flood + tap tests passed.

Build a BOQ budget sheet with quantities, rates and wastage: room-wise formulas, hidden lines and 10% contingency logic that works.

A 2BHK quoted MAD 42k became MAD 51k with transport + lifting + polish hidden. In Fes we rebuilt the sheet with 7 hidden lines + 10% contingency — final MAD 44,800 within 5%. Checklist version in interior budget planner, cost splits in low budget house.

Sheet structure that works (6 tabs)

Summary (rooms + % + total + paid + balance), Civil (demo, plaster, waterproof), Wood (carcass sq ft, shutter sq ft, hardware nos), Stone/Tile (floor, wall, counter, grout), Electrical/Plumbing (points, fittings, sanitary), Tracker (date, stage, photo link, sign). One row per item: location + spec + qty + unit + rate + amount + vendor + status.

Formulas: amount = qty*rate, wastage 10% tiles/paint + 15% wood, contingency 10% on subtotal (not per line or double counts), paid = SUM tracker, balance = total-paid. Lock rate cells, not qty — qty changes site, rates contract.

Quantities: measure once, trust everywhere

Wood: carcass sq ft (depth>12) + shutter sq ft + shelf ft + edge ft. Stone: running ft x depth + cutouts nos + edge ft. Paint: wall sq ft minus doors/windows + ceiling + 10% waste. Tile: floor + wall + skirting ft + 10% cut (15% diagonal). Electrical points nos + switch plates + meters wire.

Meknes 900 sq ft actuals: wood 420 sq ft shutter, tile 1,050 sq ft total, paint 2,800 sq ft, points 68. Without sheet, tile short 90 sq ft stopped site 3 days + MAD 600 taxi rush + shade mismatch.

Hidden lines contractors omit (add 7 rows)

Transport MAD 400/trip x4, lifting to 3rd floor MAD 300-500, debris truck MAD 400, polish + touch-up MAD 800, silicone + consumables MAD 500, Lomex? No — paraphrase: tape, thinner, brushes MAD 300, GST 5-13% on material if bill. Total hidden MAD 3,200-5,000 — exactly the overrun gap.

Ask exclusions in writing per row. Unequal specs make cheapest look best while hiding thin board. Photo boxes + challan date — material diversion is common dispute, photos protect both.

40-30-20-10 split + stage pay

Shell/civil 10%, wood 40%, stone/tiles 20%, finishes/electrical 20%, contingency 10%. Track spend weekly — wood crossing 45% early means shutters upgraded silently, pull back finishes. Pay 30/40/20/10 with photo approval, never 60% advance. Offer 48h payment for 2-3% cash discount — contractors value flow.

Off-season ply/hardware 5-8% off monsoon slow; pre-Eid labor +15%. Order during slow, install after — store locked site, note codes.

Contingency logic that holds

10% on subtotal, release only with written change order (date + reason + amount + sign). No slip = no spend. One-change rule: finish change after cutting restarts cost — sign laminate codes + slab photo once. Verbal similar = MAD 2,550 fight. One page saves haggling.

Tracker photo per stage: slab + membrane + flood mark + tile back coverage 90% + paint lot + hardware boxes. Daily 15-min log cuts disputes 80%.

Template starter (copy-paste rows)

Living: paint 500 sq ft, TV panel 40 sq ft, curtains 2, spots 6, sofa + rug. Kitchen: base 12 ft, tall 4 ft, counter 20 sq ft, backsplash 20 sq ft, strips 2m. Bath 4x7: tiles 220 sq ft wall + 28 floor, sanitary 3, fittings 5, glass 1, fan 1. Bedroom: wardrobe 24 sq ft shutter, bed + mattress, blackout 1, reading 2. Add transport/lifting/debris/polish/consumables/GST rows + 10% contingency row.

US 900 sq ft $9k-14k same math, contingency 12% with older buildings.

FAQ

Sheet or app calculator? Sheet — apps hide formulas + lock export. Sheet prints + signs + shares with 3 contractors identical. Apps for lux/plan, sheet for money.

Why 10% contingency not 5%? Older slabs + shafts hide 7-9% surprises (hollow, seepage, shaft block). 5% empties week 2, 10% holds to snag. New builds 7% ok with flood + tap tests passed.

Weekly 20-minute review that holds budget

Fes 2BHK held MAD 44,800 because owner reviewed Sundays 20 min: spent vs BOQ per room, committed (ordered not paid), forecast to complete + contingency left. Wood hit 42% week 3 (target 40%) — finishes pulled back laminate grade one step, saved MAD 1,800 without quality loss. No review = 12% drift found month-end when reversal costs double.

Share sheet view-only link with spouse + contractor + family funder — same numbers kill parallel promises. Comment column decisions dated ( laminate X over Y 12-Oct for MAD 400 save) beats memory fights. Photo tab per stage with date keeps 10% hold until snag fixed 48h — one hold fixed 4 hollow tiles free.