Draw Various Roof Shapes
Sketch the whole house to experiment with porch designs. Use graph paper to draw the front facade, so the porch roof looks harmonious with the size of windows and house overhangs. You can sketch a porch with a single sloping roof or a hip roof, for example. The porch roof or structure should not overpower the size of a single-level home in any way.
Follow Local Building Codes
Define allowable space and any conflict areas. For example, measure how much floor space you can allow for the porch base. You will need to consider property lines, sidewalks and other issues. Get a copy of building codes to examine any restrictions on roof designs before you finalize plans or approach city officials for a building permit.
Define Complementary Overhangs
Roof overhangs should complement the house. Be sure to draw roof overhangs and soffit areas to fit the current lines of the house. You will need to add guttering and downspouts, so make sure the porch looks as if it's original to the construction of the house. The roof design may need to tie in with house rafters, especially if winds are strong. Plan to bolt the porch framing to the house roof rafters rather than using nails or screws.
Choose Materials Wisely
The porch foundation should match the home's foundation. For instance, if your foundation is covered by stone veneer, the porch foundation should have this same look in most cases. While a concrete or wooden porch is an acceptable design, make sure it looks correct with your home's exterior materials from every aspect. Never make the porch foundation stand out on a single-level home. Too many steps in red brick, for example, will pull attention away from the house itself.
Design Sound Porch Framing
Plan good structural framing before proceeding with construction. Draw all framework for the porch and its support columns, plus the porch flooring design. If you plan to add stone or tile work to the floor base, you will need to do this before installing pre-made columns on the porch, for example. If you plan to enclose part of the porch in glass or siding, design solid structural support, so the enclosure's siding or glass sections support no actual roof weight.