The most common reason why homeowners get water in their basement or garages is because of clogged gutters and poor or even non-existent foundation grading.
You can prevent all those costly repairs and insurance claims by doing your own french drain over the weekend!
You will need to dig a trench along the outside of your footing. Depending where you will install the French drain will determine how much you should dig, for a basement the trench will be as deep as 6 feet and 2 feet wide and as shallow as two feet for a slab-on-grade home.
After you dug up and exposed the foundation it is always good to inspect it and see if you have any cracks in the foundation. In order to do that you will need to wash away the dirt from the foundation. After you washed off all the dirt you would want to seal the seam where the foundation wall meets the footer by applying a rubber like sealer/crack filler, the best option would be to apply a polyurea coating since polyurea is elastomeric and a very strong coating, it will not crack with temperature changes.
After you have filled in the cracks and coated the exposed foundation, lay the perforated pipe on bare soil. It is very important that the pipe will always be sloped from a higher starting point to an lower elevation discharge point, and gravity will force the water out. You need to make sure that you grade or have a slope away from the house foundation, that will ensure that the water is directed away from the walls of the home.
If you are planning to have a daylight discharge french drain, make sure the discharge pipe is solid (no holes) and it runs at least 12 feet away from the foundation. (see image below)
Next you will ne to cover the pipe with at least 12 inches of washed gravel or river stone.
You will lay filter fabric over the gravel to prevent any soil from getting in to the pipe and eventually clogging it.
When done back-fill the foundation with topsoil back to its original grade height and you can replant grass to make it all look nice.