This is a very simple mod I put together for my own use, but have been asked to release.

It contains a single .esp file that adds Hearthfire house materials to leveled lists such that they will appear in dungeons or carried by enemies, or sold by blacksmiths.

There are two new lists that have been created for this purpose.
HouseMaterialsSmall100

• Nails (1, 5, or 10)
• Hinges (1 or 2)
• Locks (1)
• Iron Fittings (1 or 2)
  

HouseMaterialsLarge100

• Firewood (1)
• Goat Horns (1)
• Clay (1)
• Quarried Stone (1)
  

These lists are integrated into existing lists.

HouseMaterialsSmall100:

• LootCWImperialsIngots10
• LootCWSonsIngots10
• LootBanditIngots10
• LootBanditIngots05
• LootSmallTreasure10
• LitemBlacksmithMineralsProcessed75
  

HouseMaterialsLarge100:

• LootCWImperialsIngots10
• LootCWSonsIngots10
• LootBanditIngots10
• LootBanditIngots05
  

Clay and Straw are also added to the list LItemFurnitureMiscItems75Long story short, you may find already-made locks and hinges in bandit camps, or nails in the corpse of an unlucky mudcrab.