Storing firewood against a house in order to keep it from getting wet may seem like a good idea, however it can actually create a potential fire hazard. Firewood if exposed to direct sunlight and high temperatures over long periods of time can lead to spontaneous combustion, where the wood will ignite and spread quickly to the house. To prevent this situation from happening try storing firewood in a "lean to" or isolated area where if the wood was to catch fire it would not spread to the house. Another reason to store firewood away from a house is to prevent moisture intrusion. Moisture can get trapped between the firewood and wall of the house, eventually the water will find its way into the wall creating a whole other set of problems.