The interior cost estimate and procurement: how purchasing works under a design project

Of all the interior design project's documents, the cost estimate is the one that changes most often once construction begins. By that point the layout is usually fixed and the visual concept approved, but the estimate keeps moving: items get more expensive, go out of stock, get replaced, or arrive not quite as expected.

> From here on, by “the estimate” we mean the interior procurement estimate — the cost of final finishing materials, furniture, lighting, plumbing fixtures, equipment and other items in the project. The contractor's estimate for construction and installation work is a separate document, and the contractor calculates it.

Budget, estimate and furnishing schedule: what's the difference

In conversations about money, three different things usually get mixed up.

Budget — the amount or range the client is prepared to put towards construction. At the start it often exists as a financial framework, rather than a detailed calculation of specific items.

The furnishing schedule — a list of the project's specific items: manufacturer, collection, item number, finish, size and quantity. It's not about money, it's about the items; it may have no prices at all.

The procurement estimate — what you get once current supplier quotes are added to the items on the schedule.

Hence the order in which everything appears: project → schedule → supplier quotes → estimate → purchase.

Confusion arises when people expect the estimate at the first meeting. What can honestly be quoted at a first meeting is the design fee — it's calculated from the floor area and the package: from €50/m², from €80/m² or from €110/m² per square metre. The cost of construction before there's a layout is guesswork.

What's included in interior procurement

Procurement is the selection, purchasing and management of every item specified in the interior design project: final finishing materials, furniture, lighting, plumbing fixtures, equipment, textiles and decor. Alongside the items themselves, the work includes the specification, the purchasing table, delivery tracking, logistics, receiving goods, checking invoices and finding replacements.

What's counted separately: construction and finishing work together with its materials — that goes under the contractor's estimate; design supervision is a separate service; installation and assembly only if that's specifically included in the terms.

The scale is easy to underestimate. An apartment's schedule runs to hundreds of items from dozens of suppliers, with different lead times, different return terms, and a different likelihood of mismatched deliveries.

How to read the estimate

An estimate put together clearly can be read along four axes, and it's worth going through each one before discussing the total.

The item and its specifications. Every line should show exactly what's being bought: manufacturer, collection, finish, size. A line reading “pendant light — 12 units” isn't an estimate, it's an intention: underneath it could be eight thousand a piece, or eighty.

Quantity and allowance. For tiles, an allowance is set for cutting and possible defects, but the exact percentage depends on the format and the laying pattern: a diagonal or large format produces more waste than a straight lay. Wallpaper is calculated with the pattern repeat in mind — that adds whole rolls, not percentages. Flooring depends on the laying scheme, stone on how specific slabs are cut. There's no universal percentage for all materials. What matters is that the allowance is calculated, not added as a single figure across the whole schedule.

What's left outside the estimate. The most useful part of an estimate is what's not in it: delivery, unloading, carrying up to the floor, storage before installation, assembly, mounting, connection, packaging removal. These costs are rarely forgotten entirely, but they're often left “for later”, and they surface exactly when the reserve has already been spent.

Lead times. Not “eight weeks on average”, but for the specific furniture and the specific stone.

The estimate is also a purchasing schedule

Not every item needs to be paid for at the same time, and that changes how the estimate should be treated: it's not only about the total, but about the order.

Stone, doors, the kitchen, custom furniture and some lighting have a long production cycle, so they're ordered ahead of the final-finishes stage. In-stock items, by contrast, don't need to be brought on site months before installation: they'd have to be stored somewhere, and the risk of damage grows.

The purchasing schedule is built from the furnishing schedule and the lead times, and the payment schedule follows from that. So the question “how much does it all cost” is in practice always accompanied by a second one: “in what order do you pay”.

How much procurement costs

The market has several payment models: a fixed sum, a rate per square metre, monthly support, and a percentage of purchases. None of them is the single correct one.

Our model is hybrid: a base rate of from €500/month plus 10% of the cost of the items purchased. The point is that these two parts pay for different work.

The base rate covers what exists regardless of the invoice total: keeping the purchasing table up to date, tracking lead times, negotiating with suppliers, finding replacements, approving samples, logistics, receiving goods and handling claims. This work continues even in months with almost no purchases.

The percentage is calculated on paid invoices, not on the approved estimate. The difference is practical: the fee accrues as items are actually purchased, not in advance from the planned total. If an item ultimately isn't bought, is replaced with a cheaper one, or drops out of the project, there's no fee on it.

This ties the fee to the scale of the purchase and to financial responsibility. The larger the budget for an item, the higher the absolute cost of an error, a claim, a mismatched delivery, or damage in transit. A sizing error on a sofa costing a hundred thousand and one costing a million requires equally careful checking, but the consequences of those errors differ tenfold.

A separate note on discounts. Our fee is fixed separately and doesn't depend on which supplier an item is bought from: partner purchasing terms work in favour of the project's budget rather than being hidden inside the product price. The parties are free to set the fee model however they agree in the contract — so when comparing proposals, it's worth finding out not just the size of the commission, but also who keeps the supplier discounts and bonuses. This should be clear from the contract before purchasing begins.

Where the estimate diverges from reality

Discrepancies come in three kinds, and only one of them is an error.

Prices changed. Months pass between the calculation and the purchase. In that time a supplier may change its price list because of the exchange rate, logistics, raw material costs or its own pricing policy. That's not a mistake in the estimate, it's the estimate's shelf life.

The item has been discontinued. Furniture collections get updated, light fixtures are discontinued. A replacement is needed, and it should be chosen by whoever remembers why the original item was picked. For a light fixture that might not be the shape, but the colour temperature, the wattage and the mounting method; for a fabric, not the colour, but the abrasion-resistance rating. A replacement chosen “by the picture” looks similar and behaves differently.

The scope grew on site. The floor was opened up — underneath is a screed that needs redoing. That falls under the contractor's estimate, but it's the same person paying, so it makes sense to keep one shared reserve.

A reserve isn't a sign of uncertainty — it's part of the calculation. Its size depends on the condition of the property, the stage of the project, the share of made-to-order and imported items, and how thoroughly the apartment was surveyed before work began. There's no universal percentage here, and a figure like “set aside this much” means nothing without an assessment of the specific property.

Procurement and design supervision are not the same thing

The two are constantly confused, even though the areas of responsibility are different.

Procurement answers the questions: what to buy, from whom, at what price, when to order it, when to deliver it, and whether the delivery matches the order.

Design supervision answers something else: whether the construction matches the project, whether the contractor is implementing the decisions correctly, and what clarifications are needed on site.

Supply and logistics are procurement. Checking that the project is being built correctly is design supervision. On the site these are also separate services with separate pricing: supervision is charged monthly, from €700/month.

What to ask before signing

Five questions worth getting the answers to in writing.

1. How the fee is calculated, and what the percentage is taken from — the approved estimate or the paid invoices. The difference can be significant.
2. Who keeps the supplier discounts and bonuses.
3. Who receives the goods, files claims, and is responsible for storage.
4. Whether finding a replacement is included if an item is discontinued.
5. Who pays for delivery, unloading, carrying up, installation and storage.

None of these questions is awkward to ask. What becomes awkward is not asking them — in the third month of construction, when it turns out the reserve has run out and half the furniture still hasn't been ordered.

How procurement connects to the interior design project

Under the contract procurement can be a separate service, but as a process it's a direct continuation of the design work. The schedule is put together from the same decisions made in the interior design project: if the project specifies a built-in wardrobe with a particular depth, the schedule will include hardware for that exact depth, not something similar.

That's why, for items with a long production cycle, it makes sense to bring procurement in before the technical documentation is fully finished — as soon as a specific item is approved and its dimensions and specifications can no longer be changed without revising the project. This isn't about buying everything in advance, but about placing early orders for the items that would otherwise not be ready in time for their place on site.