Understanding how to build a spring house means knowing the importance of getting the floor build right. Once you have decided on the walls, plan the exact spot for this structure to go.
Dig a trench equal to at least a 10-foot square with the depth of at least 6-inches. The floor depth keeps the concrete from cracking due to ground contractions during the change of seasons. Check your local university extension office to determine your areas frost lines.
Locate the diversion trench against the side of the structure closest to the creekbed. Dig out a 3-foot wide trench the depth of the creekbed. Dig the trench from either side of the spring house to where the trench will turn towards the creekbed. Do not break through the creekbed yet.
Construct the framework for the floor from the 2-by-4 lumber. You will have two frames; a very large rectangle and a narrow rectangle. The wide rectangle will frame out the walkable floor space. The narrow rectangle will form the floor between the wall and the trench. You want the narrow frame at least the width of the wall because one wall will be resting on the concrete.
Lay a 1-inch layer of gravel inside the frame. Rake it level. Pour in the concrete to fill the frame. Use a wood beam and a helper to level the floor and remove air bubbles. Move the beam back and forth while moving along the length of the floor. Allow the concrete 24 hours to cure.
Determine if you will be using concrete, stone or wood for the trench inside the spring house. Each has pros and cons to work with. Stone lasts the longest, but requires some mason skills to build the walls. Wood is the easiest to use but will rot and have the shortest life. Concrete can be long lasting but requires framework and time to settle.
Block off the trench with 2-by-4 lumber and construct the walls the length required for water to flow through the building. Use a good layer of gravel for the trench floor. This way the water will not pick up any contaminates from the soil.