garage floor drain

by Ken

Q. It appears your topic about installing trench drain or square drains is for new construction. Can they be installed in an existing garage floor? I live in Wisconsin and our winters leave me with a wet mess. My garage is a three car attached and insulated but I don't heat it. My concrete floor slopes to the doors with a 2" pitch and then water puddles at the end of the cars and the garage door. Any suggestions? Thanks.

A. A trench drain can be installed into an existing garage floor by cutting the concrete about 8 inches wider and longer than the piece of trench drain. Install the piece of trench drain as per directions. Then you cut a hole into the foundation wall for the drainage pipe to exit. Dig a trench on the outside of the foundation to lay the drain pipe and pitch away from the garage.

If you set the trench drain in the low spot of your garage then all you have to do is patch the concrete floor with some Rapid Set Concrete Mix or QuikCrete 5000 lb concrete bag mix. Make sure the height of the trench drain is slightly lower than the height of the existing concrete floor.

The other option would be to cut the existing floor and set the trench drain where you thought it would be most useful. Set the height of the floor drain 1 1/2 inches above the existing concrete floor. Re-pour a new concrete floor over the existing one and pitch the new floor to the to the trench drain. The added height would mean raising your door openings. Since your garage is already finished this would be very expensive.

You could check the height of the concrete floor where the garage door closes vs the height where the water collects. If it is only slightly higher at the door opening then grinding the floor down to lower it and let the water drain out the door is probably your best option.

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