Published on January 13th, 2013 | by Henri2
Raising a sunken section of patio
Q. Our house was built in 1947 with a 9 foot by 12 foot patio. In 1976 we increased the patio to 14 feet by 26 feet by adding to the original on three sides. Since then the yard side of the original patio has been sinking and is now about 2-1/2 inches lower than the added sections. Is there a product that can be added to smooth the entire surface to correct this problem? We are considering using an aggregate surface; is this a good choice?
Before we tear up the whole patio to replace it, we would really appreciate any help you can give us.
A. You should investigate why the yard side of the original patio has been sinking since 1976 when it had remained level for the previous 29 years. Something is happening, such as settlement of the soil under that side. That needs to be addressed or any topping you add to the affected area will increase the weight of that section and could cause further settling; the way you describe the condition makes it sound as if the settling is an ongoing condition.
However, if you know that the settling has been stable for quite a number of years, you may want to risk adding a topping.
But the best way to take care of the problem, if you have enough space between the top of the patio and any doorsill is to add a 4-inch layer of concrete over the existing, you can cap the entire patio. But make sure that reinforcing mesh is used and properly set within the concrete or, better yet, a grid of reinforcing rods is used to securely bridge the sunken area.
An exposed aggregate finish, when done by experienced concrete finishers, is beautiful.by