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Sloping Or Uneven Upstairs Floor
A marble rolls across the bedroom floor, or a wardrobe no longer stands level against the wall.
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What's happening?
Almost every old house has floors that are not flat, and most of that is history rather than a fault: timber has dried and crept over a century, walls have settled a little, and the floor has followed. What matters is whether the slope is old and stable or new and moving. A long, gentle dish across a whole room usually reads as historic. A localised dip, a floor that steps down sharply at one point, or a slope that has appeared or worsened recently is a live problem, and it usually traces back to a joist that has lost support — decayed at the end where it bears into a damp wall, notched too deeply, or left unsupported when something below it was altered.
What usually causes it?
- Joist ends decayed where they bear into a damp external wall or an old chimney breast
- A load-bearing wall below removed or altered without adequate support for the floor above
- Chimney breast removed at ground floor level leaving the upper breast and joists poorly supported
- Joists notched or drilled too deeply for services, letting them sag under load
- Joist span too long for its section after a room was opened up
- Foundation movement dropping one wall relative to the other, so the floor slopes with it
- Historic creep and shrinkage in old timber, which is stable and needs no structural repair
Is it dangerous?
Old, stable slopes are not dangerous, and levelling them for its own sake is rarely worth the disruption. Take it seriously when the slope is new, has increased over months, is accompanied by fresh cracks in the walls or ceiling below, has a distinct localised dip, or coincides with a wall or chimney breast that was removed. A joist that has lost its bearing is a genuine structural fault. Approved Document A is the standard the floor was meant to meet, and a floor that has dropped since work was done downstairs points at that work.
Can I fix it myself?
Measure it, which tells you a lot. Run a long spirit level or a laser line across the room and note the fall and where it happens — a smooth dish across the whole room versus a sharp step in one place are different diagnoses. Mark and date the measurement so you can repeat it in six months. Do not level a sloping floor with screed or self-levelling compound until you know why it slopes: adding weight to an already sagging floor makes it worse, and it hides the evidence.
When should you call a builder?
Call a builder if the slope is new or getting worse, if there is a localised dip, if walls or ceilings have cracked at the same time, or if a wall or chimney breast was removed at some point below. If you have no paperwork for that earlier work, ask building control what was approved. Where a joist bearing or a beam is involved, expect a structural engineer to size the repair.
What will the builder actually do?
- Survey the floor levels and record where the fall actually occurs rather than levelling on sight
- Lift boards and inspect joist sizes, spans, notches and — most importantly — the bearings at each end
- Check what is under the floor: the wall, beam or padstone that should be carrying it, and whether it is still there
- Cut out decayed joist ends and re-bear the joists clear of damp masonry, sistering where the section is light
- Install or correct the beam, padstone or support that a previous alteration left out, to an engineer's design
- Re-level the floor and reinstate decking, skirtings and finishes only once the structure is sound
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