Subfloor Condition Questions Checklist

Write down what you know about the floor construction in each room, including whether it feels solid underfoot or slightly springy when you walk across it.

Owners can usually tell a solid floor from a suspended one by sound and feel, and that single distinction shapes most of the later questions.

Look for vents or air bricks in the outside wall near ground level and note any that are blocked, painted over, buried by paving or hidden behind planting.

Ventilation openings often indicate a void beneath the floor, and blocked ones are a common thing to raise with a qualified professional.

Do not open, clear or alter ventilation openings yourself before a qualified professional has looked at how the floor is built.

Note any hatch, loose board or lifted corner that already exists, and photograph whatever is visible without removing anything further.

A view that already exists tells an installer a great deal, and photographs let you ask questions without disturbing anything yourself.

Record the age of the property and any floor work you know of, including extensions where the build-up beneath the finish is likely to differ.

Different eras and later alterations often meet within the same room, and the junction between them is where surprises appear.

Note whether any room has been converted from a garage, outbuilding, porch or terrace at some point in the past.

Converted spaces frequently have a different floor build-up from the rest of the property, even when the finish above looks continuous.

Ask a flooring installer what they would expect to find under a floor of this type and age, and how they would confirm it here.

Turning your uncertainty into their expectation is more useful than guessing, and it sets sensible expectations about preparation work.

Walk each room slowly and note where the floor creaks, dips or feels springy, marking those spots on your sketch as you go.

A mapped pattern of noise and movement is far more useful to a professional than a general statement that the floor creaks.

Note cracked tiles, opened grout lines or repeated cracks that follow the same line across a room or continue into the next one.

Repeating patterns often point to something happening below the surface, and they are worth recording before any covering is removed.

Cracking that follows a consistent line should be raised with a qualified professional before a new finish is planned over it.

Check whether furniture rocks, doors catch on the floor, or the gap under a door varies noticeably from one side to the other.

These everyday irritations are useful evidence of level and flatness differences that will affect how a new floor is laid.

Note whether any of this has changed since you moved in or since a previous alteration, and roughly when you first noticed it.

Whether something is stable or progressing matters more than how large it is now, and that history lives with the people who use the rooms daily.

Look along the floor from a low position in each direction and note any visible dip, hump or slope you can see from there.

Sighting along a floor reveals falls and hollows that are invisible when standing, and it takes only a moment to do.

Write down whether the movement is worse near an external wall, a chimney breast, a stair or the middle of the room.

Location patterns help a professional separate something at the surface from something that needs a fuller assessment.

Note any musty smell that is stronger at floor level, in one particular room, or after a spell of wet weather.

Smell is often the first clue occupants notice, and its pattern through the year is information nobody can recover later.

Look for boards that have cupped or lifted, sheet material that has bubbled, or edges of a covering curling away from the floor.

These are visible signs worth asking about, and they can be photographed while the existing covering is still in place.

Do not conclude what is causing any of these signs. Describe them and ask a qualified professional to establish the cause.

Note staining, tide marks or discoloured skirting near external walls, under windows and beside anything plumbed in.

Where a mark sits tells a professional far more than how it looks, so record the position as carefully as the appearance.

Record any history of leaks, floods, burst pipes, blocked gutters or overflowing appliances, even ones dealt with long ago.

Past water events explain many subfloor findings, and owners routinely forget to mention them until the covering is already up.

Note whether a room feels cold or clammy compared with the rest of the property, and whether condensation forms on hard surfaces there.

Comfort observations are relevant background for the flooring discussion and for the wider conversation about the room.

Ask the installer what moisture questions have to be answered about this subfloor before a finish is laid, and who arranges that work.

Moisture assessment is a defined piece of work carried out by professionals, and it is far better raised early than discovered late.

Moisture testing and its interpretation belong with a qualified professional, and any figure you are given should be explained by whoever took it.

Note rooms where the floor sits higher or lower than the one next door, describing the step in plain terms such as barely noticeable or a clear step up.

Existing level differences shape what preparation is possible, and describing them plainly avoids assuming they can simply be removed.

Check whether a long piece of furniture such as a chest of drawers sits flat against the floor along its whole base.

A long straight edge already in the room is a simple way to notice variation in flatness without any equipment.

Note where the floor meets the skirting and whether the gap beneath it varies as you go around the room.

A varying gap can indicate settlement or an uneven surface, and it is something an owner can observe and photograph easily.

Ask what smoothing or preparation the installer expects, and whether it will change the finished floor height at the doorways.

Preparation layers add height, and that consequence reaches doors, thresholds and the openings appliances slide into.

How much preparation a subfloor needs is a judgement for the installer once the existing covering has been lifted.

Record every point where the floor meets a fixed feature such as a hearth, the bottom step of a stair, a chimney breast or a raised platform.

Fixed features cannot move, so they set the constraints that any preparation work has to accommodate.

Note every radiator pipe, appliance supply and waste run that disappears into the floor, and photograph the point where each one enters.

Anything that goes into the floor is something the installer needs to know about before a fixing is driven anywhere near it.

Never assume the route of a buried pipe or cable. Ask a qualified professional how their positions will be established.

Ask whether the property has heating pipes, electrical runs or ducting within the floor build-up, and how their positions would be found.

Owners rarely know the answer, but raising the question early is what stops a fixing going through a service.

Identify any access chamber, stopcock, meter, hatch or drain cover in or near the floor that has to remain reachable.

Covering something that needs to stay accessible is a common regret and a very awkward one to reverse afterwards.

Note where a floor void carries cabling for television, broadband, doorbells or alarm systems, as far as you know of any.

Low-voltage runs are easy to forget because nobody thinks of them as services until one has been cut.

Ask who is responsible for isolating or moving any service that is in the way, and whether that trade needs to attend before the flooring work.

Service work usually belongs to a different qualified trade, and arranging that visit is an owner task in many projects.

Isolating, moving or altering any pipe, cable or appliance connection is work for the relevant qualified trade only.

Write down where existing floor vents, grilles or air paths sit, and ask what is intended to happen to them under a new finish.

Vents and grilles get floored over by accident with some regularity, because they appear on nobody's list of things to preserve.

Work out how many layers of covering you believe are already down, using the height at thresholds and any exposed edge as evidence.

Multiple historic layers are common, and the number affects removal work, waste handling and the finished height.

Note any dark adhesive, old tiles or unidentified sheet material visible at an edge or under a threshold, and leave all of it untouched.

Recording that something unidentified exists, without touching it, is exactly what allows the right specialist to be involved early.

In older buildings, suspected historic materials must be assessed and handled only by a suitably qualified specialist.

Ask whether the existing covering is expected to be removed or laid over, and what determines which of those is possible here.

Laying over an existing floor is sometimes possible and sometimes not, and the reasons are worth understanding before assuming either.

Write down whether any previous floor was laid by the current occupier and whether any paperwork or product information survives.

Records of what was laid over what are unusually valuable and are often the only evidence that exists about the layers below.

Note whether the existing covering appears glued, nailed, clipped together or loose laid, judging from an edge or a doorway.

How the existing floor is fixed influences the removal work, and an owner can often tell simply by looking at a threshold.

Ask what condition the installer needs the subfloor to be in before their work can begin, and how that will be established.

Readiness is defined by the installer and the material supplier together, and asking makes their expectations explicit rather than assumed.

Ask what would cause them to stop and report a problem rather than carry on, and how you would be told about it.

Agreeing the stopping point in advance avoids a situation where preparation problems are quietly absorbed into the work.

Ask whether preparation work forms part of their work or is a separate piece you would need to arrange yourself.

Preparation is frequently excluded from the main arrangement, which is usually noticed only when the old covering is already up.

Agree in writing how any unexpected subfloor finding will be recorded, discussed and decided before further work continues.

Unknowns are normal in this work, and a written way of handling them is what keeps the process calm when one appears.

Ask which findings would need a different qualified professional to look at the floor before the flooring work carries on.

Some findings sit outside a flooring installer's remit, and knowing which ones in advance avoids an argument on the day.

Questions about floor structure, damp diagnosis and suspect materials sit outside flooring work and need the relevant qualified professional.