Look closely at the raw interiors that end up being photographed and very little of them is actually raw. The brick has been consolidated, the concrete carries a sealer, the oak has had at least one coat of oil. What people mean by unfinished is a surface that still shows what it is made of, which is a look on day one and a maintenance contract on every day after.
En bref
- Porosity, not appearance, separates a raw surface that ages well from one that stains within a season.
- Ceramics are the only common interior surface sold with a published absorption figure, and the classification is worth borrowing as a mental model for everything else.
- A penetrating treatment keeps the look and lets masonry dry out; a film-forming one protects better and can trap moisture in a solid wall.
- Stripping old paint, grinding masonry and bolting steel into oak each carry a specific, documented hazard.
Unfinished almost never means untreated
Practically every raw surface in a finished interior has had something done to it. Exposed brick has been brushed down and usually consolidated so it stops shedding dust onto the sofa. Polished concrete has a sealer, because bare concrete takes a red wine spill straight into the slab. Even a live-edge shelf that looks bone dry has almost certainly had a hardwax oil.
This matters because the treatment, not the material, is what determines how the surface behaves for the next ten years. Two identical brick walls, one left genuinely open and one given a film-forming coating, are different building elements with different failure modes. Choosing between them on the basis of a photograph is how people end up disappointed.
How open the surface actually is
Only one family of interior surfaces is sold with a porosity figure on the datasheet. Ceramic tile is classified by water absorption under EN ISO 10545-3, and the groups defined in EN 14411 are blunt and useful: porcelain (BIa) absorbs 0.5 % by mass or less, vitreous tile (BIb) sits between 0.5 and 3 %, and semi-vitreous (BIIa) between 3 and 6 %. A terracotta or quarry tile chosen for its raw, chalky look sits at the open end of that scale by design.
Nothing else in the raw-materials palette comes with a comparable number, so the table below ranks the usual suspects qualitatively, by what they take in first.
| Surface | How open it is | What marks it first | What you give up by sealing it |
|---|---|---|---|
| Unglazed brick, lime plaster | Very open | Water, salts, cooking grease | The wall’s ability to dry inwards |
| Cast or ground concrete | Open | Oil, wine, citrus acid | Some of the matt, dusty look |
| Terracotta and quarry tile | Open, and measurable | Standing water, foot traffic | Little, if the sealer is penetrating |
| Untreated solid timber | Moderately open, and it moves | Hand oil, water rings, iron | The dry, unhandled surface feel |
| Raw or blackened steel | Not porous, but reactive | Fingerprints, then rust bloom | The living patina, if lacquered |
The sealer decides more than the material does
There are two families of treatment and they behave in opposite ways. A penetrating product, typically silane or siloxane based, soaks into the pores and leaves them vapour open, so the surface repels liquid water while still letting moisture out. A film-forming product sits on top, protects much better against staining, scratches visibly, and is difficult to repair in a single patch.
On masonry that difference stops being cosmetic. Sealing an internal brick or lime wall with a non-breathable coating does not stop water arriving from outside, it stops it leaving. Salts then crystallise under the film, which blisters and peels, and the wall stays wet. The same logic applies to efflorescence: the white bloom has to be removed and its moisture source dealt with before any treatment, because sealing over it simply moves the problem under the coating.
Concrete follows the same split. A penetrating sealer preserves the matt, mineral look and offers less stain protection, while a topical film gives real protection and shows every scuff. Neither is wrong, but choosing without knowing which one you are buying is what generates most of the common mistakes made when decorating with raw materials.
Zone the room by contact, not by wall
The usual approach is to decide that one wall will be raw. A better one is to draw the room by contact: the surfaces hands land on daily, the surfaces that catch splash, and the surfaces nobody ever touches. A brick chimney breast above head height and the same brick behind a kitchen worktop are not the same specification, even though they are the same wall.
In practice that means keeping the fully open finish for the untouched zones, where the texture does all its work visually and the maintenance cost is near zero. Splash zones and hand height get the protective version, accepting that it will read slightly less raw at close range. Almost nobody notices the difference from two metres away, which is where the surface is actually seen from.
Three checks before the sander comes out
Exposing a surface usually means removing something first, and that is where raw materials stop being a style question.
Old paint. The US Environmental Protection Agency advises presuming that housing built before 1978 contains lead paint, and European practice treats pre-1949 building fabric as the equivalent risk category. Open-flame burning and dry power sanding are the two techniques to rule out; testing before disturbing paint, and HEPA-filtered extraction if it is disturbed, are the baseline.
Masonry dust. Cutting, grinding or blasting brick and concrete releases respirable crystalline silica. The US construction standard, 29 CFR 1926.1153, sets a permissible exposure limit of 50 µg/m³ over an eight-hour average with an action level at 25 µg/m³, and expects water suppression or on-tool extraction rather than a dust mask alone. It is written for job sites, but the dust in a flat is identical, and the control that works is the same one: keep it wet or capture it at the tool.
Iron in oak. Tannins in oak, chestnut, walnut and western red cedar react with traces of iron to leave a permanent blue-black stain, often appearing overnight once humidity triggers it. The US Forest Products Laboratory documents the mechanism in Iron Stain on Wood. Use stainless or brass fixings, prefer A4 (316) stainless over A2 (304) for tannic species, and keep carbon steel swarf off the timber, because contaminated stainless stains just as readily.
Living with it, answered plainly
Does an unsealed surface really need less upkeep? No. It needs different upkeep. There is less to strip and refinish, but more routine attention, and marks become part of the surface rather than something you remove.
Can raw finishes work in a bathroom? Yes, provided the specification changes with the humidity. Open masonry in a well-ventilated bathroom is reasonable; the same wall in an unventilated one is a maintenance problem waiting to happen.
What about rented flats? Freestanding raw pieces, textiles and lighting carry the look without touching the fabric of the building. Anything that involves stripping a wall back needs written permission, and in older buildings it needs the paint tested first.
How do we stop a room reading as unfinished rather than deliberately raw? By keeping the joinery, the lighting and the textiles precise. One rough plane in a room of resolved details reads as a choice, while three rough planes and unresolved edges read as an unfinished job.
Working with a large expanse of raw wall?
Texture solves part of it, but a big wall still needs a composition strategy, and the answer is rarely more objects.
See five ways to decorate a large wall without overcrowding it
Published on 16 May 2025. Updated on 16 August 2026. Sources: EN ISO 10545-3 and EN 14411 water absorption groups for ceramic tile; US Environmental Protection Agency guidance on pre-1978 housing and lead-based paint; US Occupational Safety and Health Administration, 29 CFR 1926.1153, respirable crystalline silica in construction; US Forest Products Laboratory, Iron Stain on Wood. Regulatory thresholds differ by jurisdiction and should be checked locally before any work begins.
