A flat, dense or gummy sourdough almost always traces back to one of three things: an under-developed dough, a wrong fermentation window, or an underdone bake. This troubleshooter walks through every common failure mode by symptom — flat-and-pale, dense-and-tight, gummy-in-the-middle — and what each one is actually telling you. Diagnose first, change one variable, bake again. You're not failing. The recipe is probably failing you.
Clara: "My first five loaves were all dense. The 6th wasn't. That's how it works."
The diagnostic flow (a 3-step decision tree)
Three steps, plain English:
- Look at the loaf. Crust colour. Shape. Size. Is it flat, normal-domed, exploded?
- Cut it open. Crumb structure. Tight everywhere, gummy in the middle, one giant tunnel, or just dense throughout?
- Check the symptom against the matrix below. Each symptom has 2–4 causes. Pick the most likely. Change one thing next bake.
Use the Symptom Diagnosis Wizard
Symptom Diagnosis Wizard
Flat and pancake-shaped — 4 causes
Why does my sourdough bread go flat?
Sourdough bread goes flat for one of four reasons: under-fermented dough that has no structural integrity, over-fermented dough whose gluten has collapsed, loose shaping that fails to build surface tension, or a cold retard left so long that the gluten matrix breaks down. The fix depends on which one — feel the dough at shaping (jiggly and slack means over-fermented; firm but lifeless means under-fermented) and you've already narrowed it to two.
1. Under-fermented bulk
How do you keep sourdough from going flat? To keep a sourdough loaf from going flat, watch the dough rather than the clock. The bulk ferment is finished when the dough has grown by 50–75%, shows a few bubbles at the surface, and wobbles like loose jelly when the bowl is nudged. In a UK winter kitchen at 16°C, that takes 10–14 hours — not the 4–6 hours US recipes assume. Then shape tightly and let the surface dry slightly before scoring.
Fix: See UK bulk-fermentation and cold-retard timings. Add 4–6 hours next bake.
2. Over-fermented bulk (the gluten gave up)
The opposite mistake — you let bulk run too long. The dough started off well but the gluten broke down. At shaping the dough is jiggly, slack, almost soupy. It won't hold a shape. The loaf bakes flat with a vinegary smell.
Fix: Pull bulk earlier — aim for 50–60% rise rather than 75%. Watch for the side-pull-away signal.
3. Shaping too loose — no surface tension
Why does my sourdough not hold its shape? A sourdough loaf that doesn't hold its shape usually has too little surface tension at shaping, not too little fermentation. Even a well-fermented dough collapses sideways if the outer skin isn't pulled taut. The fix: pre-shape, rest 20 minutes, then final-shape by folding the four edges into the centre and rolling the seam under. The shaped boule should hold a round on the bench for 60 seconds without spreading.
Fix: Pre-shape + 20-min bench rest + final shape. Cup-and-tighten until the surface is taut.
4. Cold retard too long
Past 72 hours in the fridge, the gluten matrix starts to break down. The dough scores fine but spreads flat in the Dutch oven. Common with bakers who tried to save a Friday-shape for a Monday-bake.
Fix: Cap cold retard at 48 hours. For longer planning, freeze the shaped loaf instead.
Dense and tight crumb — 4 causes
Why is my sourdough crumb so tight?
A tight, close crumb on a sourdough loaf almost always signals under-fermentation rather than a baking problem. The dough hasn't trapped enough gas during bulk, so there's nothing to expand in the oven. Other causes: a starter used before peak, dough hydration too low for the flour, and dough handled too roughly at shaping which knocks out the gas you did build. UK winter kitchens are the single most common reason — bulk takes much longer than US recipes say.
5. Starter wasn't at peak
You used the starter before it had doubled — or already past peak, after it had collapsed. A pre-peak starter is too sluggish; a post-peak one has exhausted its yeast.
Fix: Use the starter at peak — domed top, smells of yoghurt, doubles in 4–8 hours after feed. The float test confirms.
6. Bulk too short — UK winter kitchen
The recipe said "4 hours at room temperature." You followed it. The kitchen was 17°C. The dough was nowhere near ready. Bake came out tight, no rise, dense crumb.
Fix: Watch the dough, not the clock. In a 16–18°C UK kitchen, bulk is 8–12 hours. Use a clear-sided container and look for the 50–75% rise + side-pull-away + jiggle.
7. Hydration too low for the flour
Below 65% hydration with strong white flour, the dough is too stiff to develop an open crumb. Possible with bakers translating US recipes who haven't accounted for UK lower-protein flour.
Fix: Bump hydration to 72–75% for UK strong white. See what 75% or 78% hydration actually means.
8. Knocked the air out at shaping
Over-handling at shape time — squeezing, kneading, slapping — knocks out the bubbles you built during bulk. The loaf bakes with a tight crumb because the gas is gone.
Fix: Pre-shape gently (no pressure). Bench rest 20 min. Final-shape by folding edges to centre, not by squeezing.
Gummy in the middle — 3 causes
Why is my sourdough gummy?
A gummy sourdough is almost always under-baked, not under-fermented — even though every YouTube video blames fermentation. A loaf that pulled out the oven at 88°C internal temperature will be gummy in the middle even if the bulk was perfect. The second most common cause: cutting the loaf before it has cooled and dried for 90 minutes after the bake. Use a probe thermometer aiming for 96–98°C, and wait.
9. Under-baked (the most common cause, not under-fermentation)
Internal temperature below 92°C when you pulled the loaf out. The crumb is set on the outside but still wet through the middle.
Fix: Buy a probe thermometer (£8 from Lakeland or Amazon UK). Aim for 96–98°C in the centre. Bake 5 minutes longer than you think you need.
10. Cut too soon — the bake continues for 90 minutes after the oven
You cut the loaf 30 minutes after taking it out. Steam was still moving through the crumb, finishing the bake. Cutting trapped that steam and produced gumminess.
Fix: Cool the loaf completely on a wire rack for 90 minutes minimum. Two hours is better. The crumb sets as it cools.
11. Too much wholemeal or rye for the technique
Wholemeal and rye absorb more water and have less gluten development capacity. A 50% wholemeal loaf baked with white-flour technique will come out gummy because the bake time and temperature need adjustment.
Fix: For 30%+ wholemeal/rye blends, add 5 minutes to the lid-off bake. Aim for 98°C internal rather than 96°C.
Burnt outside, raw inside — 2 causes
12. Oven too hot, bake too short
250°C with the lid on for 25 minutes, then 230°C with the lid off for 10 — the crust got too dark too fast and the centre didn't have time to set. Common when bakers see the dark crust and panic-pull the loaf.
Fix: Drop to 230°C with the lid on; bake 30 minutes lid on, 15–20 lid off. Probe to 96°C, don't trust the crust colour alone.
13. Loaf too big for the Dutch oven
A 1 kg loaf in a 22 cm Le Creuset touches the sides as it springs. The sides burn while the top stays pale and the centre stays raw. UK Le Creuset 24 cm caps at ~800 g dough; the Lakeland 22 cm caps at 600 g.
Fix: Match the loaf to the pot. 600 g dough for a 22 cm Dutch oven; 800 g for a 24 cm; 1 kg+ needs a 28 cm.
Beautiful loaf, no oven spring — 3 causes
14. Over-proofed second rise
The shaped dough proofed for too long before going in the oven. By the time it hit the heat, the gluten had no spring left. The bake produced a flat loaf with no rise but otherwise correct in every other way.
Fix: Use the poke test — is your dough ready? Don't over-proof; the indent should spring back slowly, not vanish or stay flat.
15. Scoring too shallow
You scored 2 mm deep. The oven spring couldn't break through, so the loaf burst at a weak seam at the base instead. Looks flat from above.
Fix: See how to score a loaf for proper oven spring. Aim for 5 mm depth at 30°.
16. Dutch oven not hot enough at load
You preheated for 20 minutes instead of 45. The pot wasn't screamingly hot when the dough went in. Steam was weaker; oven spring was weaker.
Fix: Preheat the empty Dutch oven for 45 minutes once the oven reaches temperature. Not from cold to 45 min — from at-temp.
The Crumb Visual Identifier
Click the crumb that matches what you're looking at.
Match your crumb
The Internal-Temp Probe Calculator
What did your probe read?
The single most common UK home-baker mistake
What is the biggest mistake beginners make with sourdough bread?
The biggest mistake UK beginners make with sourdough bread is following American recipe timings in a British kitchen. A US recipe calling for a 4-hour bulk ferment at 24°C will under-ferment a loaf catastrophically in a UK February kitchen at 16°C — closer to 12 hours is realistic. The fix is to watch the dough's 50–75% rise rather than the clock, and to use the same flour the recipe tested with.
When to start over
If you've had two failed bakes in a row from the same recipe, the recipe is wrong for your kitchen — not the other way around. Find a UK-tested recipe (we recommend our complete UK beginner's guide to baking your first sourdough loaf), and try once more.
If you've had four failed bakes, take a week off, feed your starter twice daily for that week, and start fresh. Sometimes the starter is the problem — not the technique.
Frequently asked questions
Why does my sourdough bread go flat?
Sourdough bread goes flat for one of four reasons: under-fermented dough that has no structural integrity, over-fermented dough whose gluten has collapsed, loose shaping that fails to build surface tension, or a cold retard left so long that the gluten matrix breaks down. The fix depends on which one — feel the dough at shaping (jiggly and slack means over-fermented; firm but lifeless means under-fermented) and you've already narrowed it to two.
How do you keep sourdough from going flat?
To keep a sourdough loaf from going flat, watch the dough rather than the clock. The bulk ferment is finished when the dough has grown by 50–75%, shows a few bubbles at the surface, and wobbles like loose jelly when the bowl is nudged. In a UK winter kitchen at 16°C, that takes 10–14 hours — not the 4–6 hours US recipes assume. Then shape tightly and let the surface dry slightly before scoring.
Why is my sourdough crumb so tight?
A tight, close crumb on a sourdough loaf almost always signals under-fermentation rather than a baking problem. The dough hasn't trapped enough gas during bulk, so there's nothing to expand in the oven. Other causes: a starter used before peak, dough hydration too low for the flour, and dough handled too roughly at shaping which knocks out the gas you did build. UK winter kitchens are the single most common reason — bulk takes much longer than US recipes say.
Why is my sourdough gummy?
A gummy sourdough is almost always under-baked, not under-fermented — even though every YouTube video blames fermentation. A loaf that pulled out the oven at 88°C internal temperature will be gummy in the middle even if the bulk was perfect. The second most common cause: cutting the loaf before it has cooled and dried for 90 minutes after the bake. Use a probe thermometer aiming for 96–98°C, and wait.
Why does my sourdough not hold its shape?
A sourdough loaf that doesn't hold its shape usually has too little surface tension at shaping, not too little fermentation. Even a well-fermented dough collapses sideways if the outer skin isn't pulled taut. The fix: pre-shape, rest 20 minutes, then final-shape by folding the four edges into the centre and rolling the seam under. The shaped boule should hold a round on the bench for 60 seconds without spreading.
What is the biggest mistake beginners make with sourdough bread?
The biggest mistake UK beginners make with sourdough bread is following American recipe timings in a British kitchen. A US recipe calling for a 4-hour bulk ferment at 24°C will under-ferment a loaf catastrophically in a UK February kitchen at 16°C — closer to 12 hours is realistic. The fix is to watch the dough's 50–75% rise rather than the clock, and to use the same flour the recipe tested with.
What's next
The pillar that ties this together: complete UK beginner's guide to baking your first sourdough loaf. For specific levers: what 75% or 78% hydration actually means, UK bulk-fermentation and cold-retard timings, how to score a loaf for proper oven spring, and the poke test — is your dough ready?
