Six tasks that take hours in a renovation firm
This article is part of the series “AI for business by industry”. In construction and renovation one feature shapes the answers to the series' five questions: almost every expensive mistake here is about money in the estimate, not about the quality of a text. Typical tasks:
- Commercial offer. A description of stages, deadlines, what is in the price and what is not.
- Estimate. A list of works, quantities, unit prices, a total.
- Letters to the client. Delayed materials, the schedule of stages, extra work discovered after the start.
- Acts and stage reports. What is done, what remains, what is agreed.
- Photo reports. Captions to before and after photos, a weekly summary.
- Tasks for the crew and orders to suppliers. Lists, clarifications, reminders.
Tasks 1, 3, 4 and 6 are text, and an assistant handles text. Task 2 is arithmetic and responsibility, and the line here runs not through the tool but through what happens to this estimate when the scope changes. Task 5 touches other people's data.
Estimate: who calculates and who pays for an overrun
Article 844 of the Civil Code (version of 05.08.2026) provides that the price in a contract for work may be set in an estimate, and that an estimate may be approximate or fixed. That decides whether an unnoticed mistake is dangerous.
| What the contract says | What Article 844 says | What it means for the firm |
|---|---|---|
| Nothing about the kind of estimate | Part 2: the estimate is fixed unless the contract provides otherwise | By default the price is fixed |
| Fixed estimate | Part 3: changes only by agreement of the parties; if the fixed estimate is exceeded, the related costs are borne by the contractor unless the law provides otherwise | A mistake in quantity or unit price falls on the firm |
| Fixed estimate, the scope could not be foreseen | Part 5: the contractor cannot demand an increase, nor the customer a reduction, where the full scope could not be foreseen when the contract was made | “We did not know what was under the screed” does not help |
| Fixed estimate, a significant rise in the cost of materials or services the contractor supplied | Part 5, second paragraph: the contractor may demand an increase; if the customer refuses, the contractor may demand termination | An exception only for a significant rise in prices of what the contractor buys |
| Approximate estimate, extra work and a significant overrun | Part 4: the contractor must warn the customer in time; a customer who disagrees may withdraw from the contract, and the contractor may demand payment for the work done | The duty to warn lies on the firm |
| Approximate estimate, no warning given | Part 4, second paragraph: the contractor must perform the contract at the price set in the contract | A warning not sent costs the whole difference |
The law does not define a “significant overrun” or the form of a “timely warning”. These are questions for a lawyer and the contract; in this article we take only the text of the norm.
Hence the rule for the assistant. A mistake in an estimate is expensive because it usually falls on the firm, and a language model is not a calculator. We did not measure how often an assistant errs in estimate arithmetic, so there will be no percentage here. The rule does not depend on it: the total is calculated by a formula in a spreadsheet, not by a text answer. It is more useful to give the assistant what a spreadsheet cannot do: read a finished list and find what is missing from it.
A conditional example for UAH 54,420
The numbers are conditional; substitute your own. Renovation of an 18 m² room, labour only, the customer buys materials separately.
| Item | Quantity | Unit price, UAH | Amount, UAH |
|---|---|---|---|
| Plastering walls | 52 m² | 380 | 19,760 |
| Skim coat and painting | 52 m² | 260 | 13,520 |
| Floor screed | 18 m² | 420 | 7,560 |
| Laying laminate | 18 m² | 210 | 3,780 |
| Electrical points | 14 pcs | 450 | 6,300 |
| Waste removal | 1 trip | 3,500 | 3,500 |
| Total | 54,420 |
After work starts, a damp base is found under the old screed, and the extra work with materials costs another UAH 9,800. The firm's conditional margin on this job is 15%, that is UAH 8,163.
| Scenario | What the customer pays | What stays with the firm |
|---|---|---|
| Fixed estimate, overrun under part 3 | UAH 54,420 | 8,163 − 9,800 = −UAH 1,637, the job is at a loss |
| Approximate estimate, the firm warned in time, the customer agreed | 54,420 + 9,800 = UAH 64,220 (+18%) | UAH 8,163 |
| Approximate estimate, the firm warned in time, the customer refused | Payment for the work done | According to what was done |
| Approximate estimate, no warning was given | UAH 54,420 | −UAH 1,637 |
The difference between the second and fourth rows is UAH 9,800, and it depends not on the estimate but on whether the firm has a letter sent before the extra work began. 9,800 ÷ 54,420 ≈ 18%: whether a court would treat such an overrun as significant we cannot say; the law does not define it.
A warning letter about extra work
This is a task the assistant does well: drafting the frame of a letter that a foreman or site manager then fills with facts. The frame should have these parts:
- What was found and where. One or two sentences without conclusions about what exactly is wrong: “a damp base was found under the screed in room 2”.
- What changes in scope. Which extra works and materials are needed, not “roughly” but by item.
- What it costs. The sum you ask to add and by what percentage it raises the estimate.
- What happens if there is no agreement. Which works stop and whether the rest can continue without the extra work.
- Deadline for a reply. The date by which you expect a decision and where to send the answer.
- Basis. A reference to the clause of the contract and, if the firm's lawyer approves, to Article 844 of the Civil Code.
The basis in item 6 is what an assistant invents most easily. The article and part are checked against the text of the code on zakon.rada.gov.ua, as described in the article on AI for lawyers and accountants. The firm's lawyer approves the letter once as a template, and then the foreman only substitutes the facts.
For circumstances that do not depend on the contractor and threaten the quality of the result there is a separate norm: Article 847 obliges the contractor to warn the customer in time, and Article 848 gives the right to withdraw from the contract if the customer, despite the warning, has not removed those circumstances. A letter about poor material supplied by the customer or about their instructions that threaten quality is built the same way, but on a different basis.
Photo reports and personal data
A photo report seems safe: they are only walls. But a renovation site usually shows more.
Article 307 of the Civil Code allows a person to be photographed or filmed only with their consent; consent is presumed if the filming is open, on the street, at meetings or at public events. Article 308 of the same code, as a general rule, allows a photograph showing a person to be shown publicly or distributed only with that person's consent. A customer's flat, their relatives and belongings in a photo are not a public event.
Article 2 of the Law “On Personal Data Protection” (version of 14.06.2025) defines personal data as “information or a set of information about a natural person who is identified or can be specifically identified”. A photo with a flat number on the door, a plan with the customer's surname and a contract with passport details fall under that definition. Under Article 4 a data controller may entrust processing to a processor only under a written contract, and the processor processes data only within the purpose and scope set in it. Article 29 restricts transfer of data to foreign parties. The vendors of popular assistants are foreign, so without a clarified storage location and a contract we would not advise sending them such material. This is our reading, not the regulator's position.
✓ — allowed; ≈ — allowed on a condition; ✗ — do not give to a chat assistant. The classification is ours, built on the norms we cite; it is not legal advice.
A simple way to handle a photo report safely: the assistant does not see the photos. The foreman lists what is in the picture (“left — a skim-coated wall, right — wiring laid”), and the assistant turns the list into a summary for the customer. Whether current models recognise defects in photos accurately we did not test, so we do not rely on it.
Can I paste this into an assistant
- Does the text or photo contain the customer's name, an address, a phone number, a flat number, a face?That is how the site and the people are recognised. Yes → remove or replace with “Customer” and “Site 1”
- Is it a client's document: a contract, an act with passport details, a statement?Anonymising such a document is almost impossible, because the document is the data. Yes → do not paste; work in the firm's own system
- Are there people in the photo, workers or the customer's relatives?Filming needs a person's consent (Article 307), and so does showing (Article 308). Yes → crop without people or obtain consent
- Will the result go to the customer or to court without a human check?The assistant may name a non-existent article or a wrong sum. Yes → the total is calculated by a spreadsheet, the norm is checked by a lawyer
What it costs
According to the pricing pages checked on 18 October 2026, ChatGPT Business and Claude Team cost the same: $20 for a standard seat per month on annual billing and $25 on monthly billing. Both plans have a minimum of 2 seats. The National Bank rate on 18 October 2026 is UAH 44.8871 per dollar.
| People with an assistant | Annual billing, $ a month | In hryvnias | Monthly billing, $ | In hryvnias |
|---|---|---|---|---|
| 3 (owner, estimator, manager) | 60 | 2,693 | 75 | 3,367 |
| 5 (+ two foremen) | 100 | 4,489 | 125 | 5,611 |
| 10 | 200 | 8,977 | 250 | 11,222 |
A seat is needed not by every employee but by those who write: the owner, the manager, the estimator. How to choose between a subscription and pay-per-request is covered in the article on what AI costs for a team of ten. We did not compare specialised estimating and job-costing systems and do not give their prices.
What not to do
- Do not take the total of an estimate from an assistant's answer. The total must be calculated by a formula that you can open and check.
- Do not paste the customer's contract, passport details and address into an assistant. That is class 3.
- Do not send a warning letter without checking the norm against the text of the code. The article and part are checked, not taken from the model's memory.
- Do not send photos with people and flat plans with a name. Filming and showing need the person's consent.
- Do not rely on estimating norms and unit prices from an assistant's answer. We did not check the validity of any estimating norm and do not cite any; works paid from public funds are governed by separate rules that this article does not cover.
General rules for all industries are in the article on data for an AI assistant.
First step for one week: a register of extra work and a letter template
This task sits entirely in class 1: it contains no customer, and the result is visible on real jobs.
- Take three completed jobs and list everything that appeared after the estimate was signed: what was found, for what sum, when and how the customer was told.
- Calculate the share. The sum of extra work divided by the original estimate. Three figures will show how typical, rather than one-off, this problem is for your firm.
- Make a frame for the warning letter from the six parts above. The assistant helps with wording, and the firm's lawyer approves the text and the basis.
- Measure the delay. How many days passed between discovery and the letter. This figure decides the scenarios in the table.
- Save the template where the foreman will find it, and attach a rule: extra work does not start without the customer's reply.
Our position
A renovation or construction firm needs an assistant for commercial offers, letters and reports, not for the total of an estimate. A spreadsheet calculates the estimate, and a warning letter about extra work sent before it begins is the cheapest protection against the loss that Article 844 of the Civil Code describes for an approximate estimate. The customer's data and photos with people do not go into a chat assistant.
The position does not hold if the contract expressly sets other rules for distributing an overrun, if the work is performed with public funds under separate estimate-documentation rules, and if the firm has a contract with the assistant's vendor that meets Article 4 of the Law on Personal Data Protection, together with the customer's written consent. Then the decision is made on those documents.
Checked on 18 October 2026: the texts of Articles 307, 308, 843, 844, 847 and 848 of the Civil Code (version of 05.08.2026) and Articles 2, 4 and 29 of the Law “On Personal Data Protection” (version of 14.06.2025) on zakon.rada.gov.ua; prices on the ChatGPT and Claude pricing pages; exchange rate — National Bank of Ukraine for 18 October 2026. The estimate example is conditional and is not market unit prices. This article is not legal advice.