Trust

Corrections

When a number here turns out to be wrong, it is not quietly edited. It is published: what it said, what it says now, how it was found, and how far off it was.

Maintained by Pablo Ruiz Quintero · Updated 2026-10-05

2026-10-07

Roof replacement cost

It said: Standing seam metal on the same roof: $12,392, $880 a square, 79 per cent more than shingles, and roughly level with them per year owned.
It now says: Standing seam: $23,392, $1,660 a square, and shingles cost less per year owned too. The $12,392 was the ribbed exposed-fastener panel, not standing seam.
Why it was wrong: The comparison was typed into the page from the metal roof calculator's default panel, which is the cheaper ribbed one. Found while moving every typed price on the site onto the calculators.
Who it affected: The page's conclusion was wrong: it presented metal as a tie per year owned when, as standing seam, it is not.

2026-10-07

About forty cost pages

It said: Price figures typed into the text that had drifted from the calculator on the same page — among them a cold-climate heat pump at $17,000, a chain-link gate at about $300, a tiled tub-to-shower conversion at $5,000–10,000, one-part garage floor paint at $1.25 a sq ft, a toilet replacement at $320–900, a step of stairs at $160, concrete slabs at $6–14 a sq ft, sod at $1.50–3, fibre cement siding at "half as much again" as vinyl, and a pricier tile adding a tenth to the job.
It now says: Every one is now computed by the page's own calculator or read from its data: $19,100, about $460, $6,200–8,200, $3.75 installed, $640–720, about $250, $10–22, $2.59–2.86, about 80 per cent more, and about a fifth. Where a figure had no basis in the data, the number was removed rather than replaced.
Why it was wrong: Typed figures do not follow the calculators when their inputs change — and the labour rates were rebuilt from BLS wages this month. 424 typed amounts on 57 pages were found and converted; most matched, these did not.
Who it affected: Mostly understatements of 10 to 40 per cent in the prose, while the calculators on the same pages were right. The two that changed a conclusion are corrected in their own words above and on the siding page.

2026-10-05

Deck calculator, deck vs patio, construction cost per square foot

It said: A beam of two plies of the joist size on posts at roughly 8 ft centres; ledger bolts every 16 in; a 2 × 6 ledger and rim on small decks; species spans as a percentage of southern pine.
It now says: The beam, its posts and the footing size are read from the deck guide's tables (DCA 6 Tables 3A and 4, the same as IRC R507.5), the ledger lag screws from Table 5 by joist span, the ledger and rim never below 2 × 8, two lateral hold-downs added, and each species read from its own column of the joist table. The 16 × 12 ft example now has a 2-2×10 beam on 4 posts, not 3, and lags every 15 in.
Why it was wrong: A two-ply beam of the joist size may span only 6 to 7 ft at these joist spans, so posts 8 ft apart overloaded it; 16 in lag spacing is non-compliant past a 10 ft joist span. Found in a check of the structural pages against DCA 6 and the IRC.
Who it affected: A safety error: anyone building to the old figures would have under-supported the beam. The example deck costs about $150 more.

2026-10-05

Stair calculator

It said: Open risers: with a nosing over the gap, a 4 in sphere usually cannot pass.
It now says: Where the stair is more than 30 in above the ground, no gap between treads may pass a 4 in sphere; a 7 in riser leaves about 6 in open, so it needs a riser board, a back strip or a rod.
Why it was wrong: The nosing does not close a vertical gap (IRC R311.7.5.1). Found in the structural check.
Who it affected: A child-safety error on open stairs above 30 in. No price changed.

2026-10-05

Egress window installation cost, home addition cost

It said: A basement escape opening needs 5.7 sq ft clear, and finishing a basement requires the opening to be made larger.
It now says: The IRC has allowed 5.0 sq ft for a basement or ground-floor opening since 2018 (5.7 upstairs and under older codes); the calculator flags the band in between. Under the 2021 code a new basement bedroom needs an escape opening; finishing the rest does not, on its own.
Why it was wrong: IRC R310.2.1 exception and R310.6. Found in the structural check.
Who it affected: Some compliant openings were shown as failing. No price changed.

2026-10-05

Retaining wall cost

It said: No engineer or permit up to 4 ft of exposed wall; any surcharge needs an engineer at any height.
It now says: Design is required past 4 ft of retained soil, or 2 ft with a surcharge (IRC R404.4); a permit past 4 ft measured from the bottom of the footing or base, or with any surcharge. The calculator now flags and prices the permit separately.
Why it was wrong: The two rules measure from different points, and the tool used exposed height for both. Found in the structural check.
Who it affected: A 3½ to 4 ft block wall could need a permit the tool did not mention.

2026-10-05

ADA ramp slope calculator

It said: No guard on a home ramp more than 30 in up; a 180° turning landing 60 × 60 in; the ADA recommends 1:16 to 1:20.
It now says: Open sides more than 30 in up need a 36 in guard that stops a 4 in sphere (IRC R312.1); a U-turn landing spans both runs; the ADA's advisory note asks for the least slope possible, and 1:16 to 1:20 is a rule of thumb.
Why it was wrong: Found in the structural check against the IRC and the 2010 ADA Standards.
Who it affected: A safety omission on high ramps. Switchback ramps cost about $400 more, for the larger landing.

2026-10-05

Chain link fence installation cost, fence installation cost, frost line depth by state

It said: Chain-link posts buried a third of the fence height (16 in for a 4 ft fence); frost depths of 12 in for Arizona and California, 6 in for Texas, 18 in for Washington and 30 in for Missouri; the one-third rule described as a third of the post's length.
It now says: Chain-link posts at least 24 in plus 3 in per foot over 4 ft (ASTM F567); frost depths 30, 24, 12, 24 and 36 in, the deep end of each state's populated areas; the rule is a third of the height above ground.
Why it was wrong: The post depth was below the industry standard, and the frost depths were shallower than the codes of Flagstaff, Truckee, Amarillo, Spokane and Kansas City. Found in the structural check.
Who it affected: Posts and footings in those states would have been set too shallow. Fence prices there rise slightly.

2026-10-05

Concrete calculator, concrete slab calculator, concrete driveway cost, concrete patio cost, control joint spacing

It said: Steel required under vehicles; driveway concrete of about 3,500 psi; joints sawn within 6–18 hours, or within a day; 20 ft joint spacing for an 8 in slab; concrete shrinks about half a per cent; a thickened edge adds 15 per cent.
It now says: Steel is not a code requirement in a residential slab; with de-icing salt, 4,500 psi, 6% air and a water–cement ratio of 0.45; joints within 4–12 hours of finishing; never more than 15 ft apart; shrinkage about 0.05 per cent; the thickened edge on the 20 × 20 ft example adds 40 per cent, computed.
Why it was wrong: Checked against ACI 302.1R, ACI 332 and NRMCA CIP 6. Found in the structural check.
Who it affected: Late saw cuts and wide joints crack slabs, and an under-specified mix scales in salted winters. No price changed except through the joint lengths.

2026-10-05

Concrete block calculator, concrete crack repair cost

It said: 28 blocks per 80 lb bag of premixed mortar and 1 ton of sand per 100 blocks; self-leveller covering 12 sq ft per 50 lb bag at ¼ in.
It now says: 13 blocks per bag (Quikrete's own figure) and about 0.4 ton of sand; about 22 sq ft per bag.
Why it was wrong: The figures disagreed with the manufacturers' data sheets. Found in the structural check.
Who it affected: Small-wall mortar was under-ordered by half; self-leveller over-ordered by nearly double — the crack repair example falls by about $1,100.

2026-10-05

Siding installation cost

It said: Around windows the head flashing goes over the wrap and the sill under it.
It now says: The wrap above the window laps over the head flashing, and the sill flashing laps over the wrap below it — shingle fashion.
Why it was wrong: The order was reversed, and followed literally it sends water behind the wrap (IRC R703.4). Found in a check of the envelope pages.
Who it affected: A water-damage error. No price changed.

2026-10-05

Drywall installation cost, crawl space insulation cost, fascia board replacement cost, window replacement cost

It said: Half-inch drywall not allowed on 24 in framing and 5/8 in enough for a garage ceiling; no ignition barrier over crawl-space foam; one round soffit vent per 28 sq in; ENERGY STAR window limits from version 6.
It now says: Half-inch is allowed on 24 in walls and, hung across the joists, ceilings; a garage ceiling under rooms needs 5/8 in Type X; exposed foam needs a listed board or an ignition barrier; about one 4 in vent per 6 sq in of free area; ENERGY STAR version 7 limits (0.22 north to 0.32 south).
Why it was wrong: Checked against IRC R702.3.5, R302.6, R316.5.4 and the ENERGY STAR version 7 specification. Found in the envelope check.
Who it affected: Fire-separation and ventilation errors; a U-0.30 window no longer shows as qualifying in zone 4. No price changed.

2026-10-05

Metal roof cost

It said: A shed roof priced with panels and rakes half their real length; $8.80 a square foot, $12,392 and the other example figures typed into the page.
It now says: A single slope runs the full width; the example figures are computed by the calculator (they had not drifted).
Why it was wrong: A geometry slip in the engine. Found in the envelope check.
Who it affected: Shed roofs were understated by roughly the panel cost; gable and hip roofs were unaffected.

2026-10-05

Ceiling fan installation cost

It said: Standard (unmarked) boxes carry up to 35 lb; boxes marked with a weight go to 70 lb.
It now says: A fan-rated box with no weight marked on it carries up to 35 lb, one marked with a weight up to that weight and never more than 70 lb; a box with no fan marking carries no fan at all.
Why it was wrong: NEC 314.27(C) applies the 35 lb figure only to boxes listed and marked for fan support. Found in a check of the electrical pages against the 2023 NEC.
Who it affected: Read literally, the old wording allowed a fan to hang from an ordinary lighting box — a safety error. No price changed.

2026-10-05

Heated floors cost

It said: Floor heating GFCI-protected in a bathroom or kitchen; the electrical code keeps heating cable out from under cabinets and fixtures.
It now says: GFCI-protected in every room — the code requires it for cable or film under a floor covering — and the rule against heating under cabinets and fixtures comes from the makers' instructions, which the code makes binding.
Why it was wrong: NEC 424.45(E) and 424.99 require GFCI protection for heating cable and panels under floor coverings wherever they are; the bathroom-and-kitchen rule is for cable cast in concrete. Found in the electrical check.
Who it affected: Someone heating a bedroom floor could have left out the GFCI. No price changed: most floor thermostats include it.

2026-10-05

Recessed lighting calculator

It said: A non-IC housing needs 3 in clear all round.
It now says: A non-IC housing needs insulation kept 3 in from the housing and its driver box, none at all over the top, and ½ in from wood framing; in an insulated ceiling the energy code requires IC-rated, airtight fixtures.
Why it was wrong: NEC 410.116 forbids insulation above a non-IC fixture as well as within 3 in of it; "all round" could be read as the sides only. Found in the electrical check.
Who it affected: The old wording could have led someone to lay insulation over a non-IC can — a fire risk. No price changed.

2026-10-05

Wire size calculator

It said: The equipment ground does not grow when the conductors are upsized for voltage drop; 8 AWG can serve a 50 A circuit on 75 °C terminals; the hot tub preset was a 50 A continuous load; a DC system is not governed by the NEC.
It now says: The ground is upsized in proportion when the conductors are (250.122(B)), and the calculator now does it; the 75 °C column is only for separate THHN/THWN wires, never NM or UF cable (334.80); the hot tub preset is a 40 A load on a 50 A circuit; a battery system in a house is NEC work, a boat or RV follows ABYC or RVIA.
Why it was wrong: Four points that disagreed with the 2023 NEC, found in the electrical check. The hot tub preset sized a 70 A breaker, which no tub's nameplate allows.
Who it affected: Runs long enough to be upsized for voltage drop now show a larger ground and its cost. Anyone who used the 75 °C answer with cable would have under-sized it.

2026-10-05

Electrical outlet replacement cost

It said: A 48 A Level 2 EV charger on a 60 A circuit in 6-gauge copper, to a 240 V receptacle — about $940.
It now says: Hardwired on a 60 A circuit in 4-gauge — about $1,100. A plug-in charger is limited to a 50 A circuit and a 14-50 receptacle.
Why it was wrong: 6 AWG in NM cable is good for 55 A, short of the 60 A a 48 A charger is sized at, and NEC 625.44 limits receptacle-connected chargers to 50 A. Found in the electrical check.
Who it affected: The EV charger figure rose by about $160; the advice it gave would not have passed inspection.

2026-10-05

Electrical panel replacement cost

It said: A heat-pump water heater and a heat-pump dryer together take about 3 amps off the calculated demand.
It now says: About 13 amps: (3,000 + 5,000 VA) × 40% ÷ 240 V.
Why it was wrong: An arithmetic slip in a typed sentence; the figure is now computed. Found in the electrical check.
Who it affected: It understated by a factor of four how much changing two appliances can do against a panel upgrade.

2026-10-05

Tankless water heater cost, gas line installation cost, pool heater installation cost

It said: Gas pipe capacity from a curve fitted to the code table, at 1,030 BTU a cubic foot; the tankless check matched the run to the nearest of 20, 40, 60 or 80 ft and treated anything longer as 80 ft.
It now says: Capacity read straight from IFGC Table 402.4(1) — the same as NFPA 54 — with the length equal to or next above the run, at 1,000 BTU a cubic foot, out to 500 ft; beyond that the tool says the line needs designing. One table now serves all three pages, and 2 in pipe is included.
Why it was wrong: The fuel gas code's longest-length method reads the next longer row, never the nearest, and does not extrapolate. The fitted curve ran 2–10% above the table. Found in a check of the gas pages against the IFGC.
Who it affected: A 180,000 BTU tankless on ¾ in at 30 ft, or a long run read as 80 ft, could pass when the table says it does not. The 250,000 BTU generator at 40 ft now needs 1¼ in pipe, not 1 in. No price changed.

2026-10-05

Gas fireplace installation cost

It said: Past about 60 ft a 30,000 BTU fireplace on a busy meter often fails the sizing table; vent-free units are banned in California and Massachusetts and every manual limits their hours.
It now says: A new ½ in branch carries a 30,000 BTU fireplace well past 60 ft — what fails is teeing into a line already feeding the furnace and water heater. Vent-free units are banned in California and some cities, and where allowed the fuel gas code keeps them out of bedrooms and bathrooms, caps them at 40,000 BTU and sizes them to the room.
Why it was wrong: The pipe table does not support the first claim; Massachusetts has lifted its statewide ban; the hour limit is not a code rule. Found in the gas check.
Who it affected: The cause of the extra cost on a long run was misdescribed; the cost itself is unchanged.

2026-10-05

Solar panel calculator

It said: 8.8 kW × 4.5 h × 365 = 14,454 kWh; with a 0.78 derate 11,288, a difference of 3,166 kWh. System losses added up to 14%.
It now says: 11,274 kWh and 3,180; losses include PVWatts' 1% nameplate rating and are combined by multiplying, 14.08% as PVWatts gives it.
Why it was wrong: An arithmetic slip in a typed example, now computed, and a loss table that left out one PVWatts default. Found in the electrical check.
Who it affected: Production estimates moved by a fraction of a per cent; the example's numbers were off by 14 kWh.

2026-10-05

Furnace installation cost

It said: A 95% furnace with a shared chimney and no drain: $8,660 in one place, about $8,700 in another and about $8,300 in the introduction.
It now says: About $8,700 everywhere, computed by the furnace calculator, as are the other example prices and the sizing figures on the page.
Why it was wrong: The figures were typed into the page and had drifted apart. Found while checking the page's venting text.
Who it affected: The introduction understated the orphaned-chimney case by about $400.

2026-10-05

Concrete vs asphalt driveway

It said: Over thirty years asphalt came to $7,938 — a resurface around year 18 and a seal coat every four years at about $145 — and concrete was 26 per cent more.
It now says: Asphalt comes to $9,064 — a resurface around year 22 and a seal coat every 3 years at $250, as the asphalt and sealing calculators give them — and concrete is 11 per cent more.
Why it was wrong: The thirty-year assumptions were typed into the page and did not match the site's own asphalt and sealing calculators. Found while connecting the comparison pages to the engines; every figure on the page is now computed.
Who it affected: The conclusion holds — asphalt is cheaper over thirty years — but the gap was overstated by more than half. The day-one prices were right.

2026-10-05

Carpet vs hardwood

It said: Hardwood sanded twice at about $983 a time, $4,667 over fifty years, 45 per cent less than carpet.
It now says: Sanded twice at $1,059, $4,819 over fifty years, 44 per cent less.
Why it was wrong: The sanding price was typed into the page and had fallen behind the refinishing calculator. Found while connecting the comparison pages to the engines.
Who it affected: The fifty-year hardwood figure was understated by $152 (3%); the conclusion is unchanged.

2026-10-05

Deck vs patio

It said: A paver patio $21.41 a square foot and a poured concrete patio $13.71.
It now says: $21.00 and $13.34.
Why it was wrong: Typed figures that had fallen behind the paver and concrete patio calculators — the same error corrected on the concrete patio vs pavers page.
Who it affected: Both patio figures were overstated by 2–3%. The deck figure was right.

2026-10-05

Sources — our own price figures

It said: 145 of our own price sources were listed as surveys, with methods describing price lists and contractor quotes compiled into national ranges.
It now says: They are listed as editorial estimates: ranges set by the editor from general knowledge of the US market, not a measured survey or a sample of quotes. The figures themselves have not changed.
Why it was wrong: The description overstated how the ranges were made. Found in an internal audit against Google's quality guidance; the estimates are being replaced with sourced data, starting with federal wage data for labour.
Who it affected: Every cost page that uses one of our own ranges. No number moved; what changed is how much confidence the sources page claimed for them.

2026-09-29

Concrete patio vs pavers

It said: The same 20 × 16 ft patio is $4,386 poured and $6,850 in pavers — $13.71 a square foot against $21.41, pavers 56 per cent more.
It now says: $4,267 poured and $6,720 in pavers — $13.34 against $21.00, pavers 57 per cent more.
Why it was wrong: The figures had been typed into the page instead of computed, and the slab and paver calculators had moved on since. Found while building the concrete patio page; the comparison now runs both calculators.
Who it affected: Concrete was overstated by $119 (2.8%) and pavers by $130 (1.9%); the comparison between them was unchanged.

2026-09-29

Pavers — related links

It said: A link to the comparison described poured concrete as “56 per cent less”.
It now says: The link no longer quotes a percentage.
Why it was wrong: 56 per cent was how much more pavers cost, not how much less concrete costs — that is about 36 per cent. Found with the correction above.
Who it affected: A description on one link; no calculation used it.

2026-09-28

Toilet replacement cost

It said: The citation for flush volumes and WaterSense pointed to the EPA's outdoor water use statistics.
It now says: It points to the EPA WaterSense specification for high-efficiency toilets.
Why it was wrong: Two sources shared one identifier, so the second silently replaced the first. Found while building the lawn mowing page; the build now fails if an identifier is repeated.
Who it affected: The citation only. The flush volumes and savings on the page were right.

What counts as a correction

A figure that was wrong, a formula that was wrong, or a default that was wrong for the case it was applied to. Anything that would have changed what you ordered or what you expected to pay.

Routine updates are not corrections — a price that moves because the market moved, or a dataset that publishes a new year, goes in the changelog instead. The difference is whether the old number was wrong at the time it was published, or simply old.

How to report one

Name the page and the number. If you can, say what you think it should be and why — a data sheet, a code clause, a supplier quote. We will check it against the source and, if it is wrong, it appears here with the date it was fixed.