Grout is the unsung hero of any tiled surface — but it’s also the first thing to show its age. Discoloured, cracked, crumbling or mouldy grout can make an entire bathroom look tired even when the tiles themselves are in perfect condition. Understanding the difference between grout that needs cleaning, grout that needs repair, and grout that needs full replacement will save you time, money and unnecessary disruption.
The Different Stages of Grout Deterioration
Stage 1: Discolouration and Staining
White and light grey grout in showers and around baths is particularly prone to discolouration from soap scum, limescale and hard water deposits. In many cases, heavily discoloured grout can be restored by professional cleaning using appropriate grout cleaners and mild acids (safe for the grout, avoiding the tile surface). If the grout is still structurally sound, deep cleaning is far cheaper and less disruptive than regrouting.
Stage 2: Mould
Black mould in grout joints is extremely common in UK bathrooms — particularly in poorly ventilated rooms. Surface mould can sometimes be removed with a mould spray and a stiff brush, but mould that has penetrated into the grout itself cannot be removed: it needs to be raked out and the joint regrouted. This is a targeted repair that doesn’t require regrouting the entire surface.
Stage 3: Cracking and Crumbling
Grout that is cracking or crumbling is failing structurally. In isolated areas this is often caused by movement at an internal corner or junction — these are natural movement joints that should have been filled with flexible silicone rather than rigid grout. The solution is to rake out the cracked grout, consider whether the movement joint needs silicone rather than grout, and re-fill accordingly.
Stage 4: Widespread Failure
Where grout has failed across a large area — crumbling throughout, fully open joints, water ingress evidence — full regrouting of the area is the appropriate response. This involves raking out all the old grout to a sufficient depth (typically 2–3mm minimum), cleaning the joints and applying fresh grout. On wall tiles, this can usually be done without disturbing the tiles themselves.
Silicone vs Grout at Internal Corners
One of the most common tile maintenance errors is using rigid tile grout at internal corners (where a wall meets the bath, or where two walls meet) rather than flexible silicone sealant. Internal corners are movement joints — the substrate behind the tiles moves slightly as the building settles or as temperature changes, and rigid grout cracks under this movement. The correct approach is silicone at all internal corners, grout everywhere else.
Get a Grout Repair or Regrouting Quote
Shazam Repairs provides specialist grout cleaning, repair, replacement and silicone renewal across the UK. Send photos for a free assessment — in many cases we can advise whether cleaning or repair is sufficient before you commit to regrouting.
