Why Is My Sourdough Flat

A flat sourdough is one that spreads sideways in the oven instead of rising up. It may still taste good, but the crumb is often dense at the edges and the slices are wide and low. The good news is that this is one of the most fixable sourdough problems, because each cause leaves recognizable signs in the dough before it is baked.

Think of a tall loaf as three things working together: enough gluten strength to hold gas, the right amount of fermentation, and a shape with a taut outer skin. When one fails, the loaf slumps. A weak starter or an oven that is not hot enough can make any of those problems worse.

Weak gluten and too much water

If your dough feels like batter after an hour, pours out of the bowl and will not hold a fold, it lacks strength. That can come from too much water for the flour, too little mixing, or a low-protein flour. High hydration open-crumb recipes look tempting online but need strong flour and practice.

Lower the water by 5 to 10 percent of the flour weight, use bread flour with around 12 to 13 percent protein, and add one or two extra sets of stretch and folds or coil folds in the first two hours of bulk. The dough should become smoother, springier and able to hold a rounded shape by the end of bulk.

Over-proofing

Fermentation that runs too long lets acid and enzymes weaken the gluten while the gas cells grow too thin to hold up. Over-proofed dough looks large and bubbly, smells strongly sour or alcoholic, feels slack, and sighs or deflates when you turn it out or score it.

Shorten the stage that ran long. If bulk took the dough past double, end it sooner, around a 50 to 75 percent rise. In a warm kitchen, use cooler water to start. For the final proof, use the poke test: a floured fingertip dent that springs back slowly and only partly is ready; a dent that stays fully is past it.

Shaping without enough tension

The final shape builds a skin of stretched gluten that acts like a balloon wall. A loose shape lets the dough sag as it warms in the oven. During shaping, fold the dough over itself and then roll or drag it toward you on a lightly floured counter so the surface tightens and looks smooth.

Seal the seam well and place it seam side up in a well-floured banneton. A banneton that is too large for the dough also lets it spread; aim for a basket the dough fills by about two-thirds before proofing.

Starter strength and temperature

A sluggish starter makes dough that rises slowly and unevenly, which tempts you to wait too long. Before baking, your starter should reliably double within 4 to 8 hours of a feeding at room temperature. If it does not, give it a few days of regular feedings first.

Dough temperature controls pace. Target about 24 to 26°C (75 to 79°F) after mixing. Cold dough can still be under-fermented after many hours; very warm dough can over-proof before you notice.

Getting the oven spring

Spring happens in the first 15 to 20 minutes of baking, while the crust is still soft and steam keeps it supple. Preheat a lidded Dutch oven for 45 to 60 minutes at 250°C (480°F), load the loaf, bake covered for 20 minutes, then uncover, lower to 230°C (450°F) and bake until deep brown.

A cold, firm dough from an overnight retard holds its shape better during transfer and scores more cleanly. Score with a decisive cut about 6 to 12 mm (¼ to ½ inch) deep; a shallow score can seal over and force the loaf to burst sideways.

Quick checklist

Work down this list on your next bake and change only one item at a time.

• Dough held a dome at the end of bulk
• Rise during bulk was 50 to 75 percent, not double or more
• Surface after shaping was smooth and taut
• Banneton fit the dough size
• Poke test: slow, partial spring back
• Pot preheated fully; loaf baked cold

Common questions

Should I just bake my sourdough in a loaf pan?

A pan solves the spreading and makes a good sandwich loaf, but it hides the problem. If you want free-form loaves, use the pan while you work on strength and shaping, then go back to the Dutch oven.

My loaf was tall in the banneton but flattened when I turned it out. Why?

That points to over-proofing or a weak skin. A properly proofed, well-shaped dough holds its shape for a minute or two on parchment. Try a shorter proof and a slightly tighter shape.