I have a sun porch on the back of my house that floods every time it rains. My backyard is sloped where the water runs toward the house. The water seeps in from underneath the walls. I am looking for ways to stop this flooding -- maybe digging a trench or getting some type of material to block the water. Please help.
Regina, the only sure methods for preventing your sun porch from flooding during a rain are to adjust the grade or to install some sort of a drainage system. I would recommend consulting with a landscape contractor as they should be able to look at your yard and provide the best option for your situation.
Adjusting the grade would involve making the slope toward the porch a little steeper, but creating a low point several feet from the structure. There would then be a small slope from the porch to the new low point or swale that has been formed. This new swale would parallel the porch and then drain away from your home. Depending on the slope of the swale, a drain tile may have to be installed below grade to assist with the water drainage. This is called a French drain and is often used in yards where proper drainage can be an issue.
If your yard's grade can't be adjusted due to landscaping or other obstacles, then a drainage system of some sort could be installed where the slope meets the porch slab. This drain might consist of a surface grate that allows the water to flow into a drainage trough and away from the porch or a below grade French drain. In both cases the water would need to be carried to a point where it can naturally drain away from your home.
Any material that you install to block the water will more than likely just be a temporary fix. Water has a way of eventually finding its way past just about anything unless given a path of less resistance such as a drain. A good landscape contractor should be able to eliminate your flooding problem and blend the drainage system into your yard so that it's barely noticeable.
One thing to keep in mind though is that any drainage system must be kept clean to work properly. That means removing grass clippings and other debris on a regular basis to keep the water flowing and off of your porch.