Next time you are waiting for a bus, queueing outside a pharmacy or sheltering from the rain under a shop awning, try something different: look up. Above the modern fascias and the sign-written vinyl, most British high streets are still wearing their original clothing. Ground floors are reinvented every decade or so, but the upper storeys have often survived untouched since the day the builder handed over the keys. Learning to read those details turns an ordinary errand into a free architectural treasure hunt, and it costs nothing but a crick in the neck.

Why the First Floor Tells the Truth

Shopkeepers have always been pragmatists. A new owner with a modest budget will repaint a fascia, clad a pilaster, drop in a suspended ceiling and call it a refit. Very few will pay to alter the brickwork two storeys above their heads, because nobody complains about a chimney stack. That is why the first and second floors are the most honest part of any commercial building. They preserve the proportions, materials and decorative fashions of the decade in which the terrace was built, and they frequently contradict the impression given at street level.

Start by standing back on the opposite pavement and asking three questions. What is it made of? What is it pretending to be? And when was it last altered? The answers are usually visible within a minute.

Brickwork Is a Datestamp

Brick is the great tell-tale of British building. The way bricks are laid, not just their colour, gives you a rough date.

• Flemish bond — alternating headers and stretchers in each course — was the fashionable choice for polite Georgian and early Victorian fronts, often with the headers burnt darker to create a subtle chequer.
• English bond, with whole courses of headers and whole courses of stretchers, is generally earlier and sturdier, common in the seventeenth and eighteenth centuries.
• Rat-trap bond, where bricks are laid on edge to leave a hollow wall, is a Victorian economy trick. It is surprisingly common behind render on terraces built between roughly 1830 and 1900.
• Polychrome and diaper work — red, blue-grey and buff bricks arranged in diamonds or bands — belongs firmly to the later nineteenth century, when showy Nonconformist chapels and proud corner pubs competed for attention.

Then look at the arches above the windows. A gauged brick arch, with thin, precisely cut bricks and a faint rise, is a sign of money and skill. Notice too whether the mortar is a neat, thin line with a slightly grey, almost metallic sheen: that may be tuck pointing, a Victorian conceit that made cheap brickwork look sharper than it was.

Carved Stone, Terracotta and Stucco

Not every front is brick. Stone, or something pretending to be stone, has its own vocabulary. Run your eye along the parapet and cornice, then down again.

• Datestones and keystones carved with a year, or with initials and a year, are the single most useful clue you will find. They may commemorate a builder, a founder, a marriage or a rebuild after fire.
• Corbels, brackets and consoles supporting a cornice or a bay often carry faces, acorns, leaves or scrolls. Coarse, chunky carving suggests a local mason; crisp, fussy detail suggests a pattern book.
• Terracotta — buff, cream or reddish, with a slightly smooth, almost soapy surface — was hugely popular from the 1860s onwards for its sharp mouldings and resistance to soot. Look for terracotta panels, friezes and window surrounds on late Victorian shopping parades.
• Stucco and render may be scored with false joints to imitate ashlar, and may be hiding earlier brick, timber framing or a former shopfront altogether.

Ghost Signs and Vanished Shopfronts

The upper floors are also an archive of commerce. Faded painted lettering on a gable end — a "ghost sign" — often advertises a trade that vanished before your grandparents were born. Look for the shadow of a removed fascia in the brickwork, where cleaner stone or darker brick outlines a previous nameboard. Other clues are less obvious but just as revealing.

• Blind boxes: the square timber housing above a shop window that concealed a roller shutter. If the shop now has a modern shutter outside, the old housing is often still there, painted over.
• Iron brackets and stubs in the brickwork that once held hanging signs, gas lamps or awnings.
• Thresholds of stone or mosaic tile, worn into a dip by a century of feet, sometimes spelling out a shopkeeper's name.
• Boot scrapers, coal chutes and cellar hatches in the pavement, quietly marking where a household once kept its coal and cleaned its shoes.

Windows, Ironwork and the Small Print

Windows are where a building shows its age most clearly. Slender glazing bars and a shallow reveal suggest an early nineteenth-century sash; thick, chunky bars and horns on the sashes point to later Victorian or Edwardian work. Stone cills, rubbed brick lintels and cast-iron balconettes all repay a second glance.

The real prize, though, is the rainwater goods. Cast-iron hopper heads — the flared funnel at the top of a downpipe — were frequently cast with the maker's name, the town of manufacture and a year. Finding one stamped with a local foundry and a date in the 1880s is like finding a signature on a painting. Similar details appear on drain covers, railings and the iron cresting along a parapet.

How to Investigate and Record What You Find

Once you start noticing, you will want to know more. Your local record office or archive will hold old Ordnance Survey maps, trade directories and photographs that can pin a building to a date and a trade. Many councils publish descriptions of locally listed and statutorily listed buildings, which are goldmines of precise detail. Local history and civic societies often run walks and welcome new eyes.

Keep a simple notebook or a phone note with the address, the date, and one or two specifics: the year on the keystone, the pattern of the brickwork, the name on the hopper head. Photograph details square-on, and put something familiar in the frame for scale. Stay on the public pavement, never trespass, and resist peering through windows. Look up, note it down, and your high street will never look ordinary again.