The answer to 'why is my deck drainage problems' is that poor deck drainage can be caused by a few common issues, like improper grading, clogged drains, or damaged downspouts. Symptoms include standing water, rotting wood, and mold growth. To fix it, you'll need to assess the drainage system and make necessary repairs or adjustments.
First, check the grading around your deck. The ground should slope away from the deck at a 1-2% grade to encourage water runoff. If the ground is flat or slopes towards the deck, you may need to regrade the soil. You can also install a drainage system like a trench drain or catch basin to divert water away.
Next, inspect your deck drains and downspouts. Make sure they are clear of debris and directing water at least 6 feet away from the deck. Damaged or clogged drains may need to be repaired or replaced. Finally, check for any cracks, gaps, or damage in the deck boards that could be allowing water to pool.