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Rick
Rick, General Contractor
Category: Home Improvement
Satisfied Customers: 18891
Experience:  Licensed construction supervisor with 35+ yrs. experience.
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I needed to install a French drain to a downspout on my garage.

This answer was rated:

I needed to install a French drain to a downspout on my garage. I had to cut 6 feet of concrete away to have the drain installed. So now I have a cement trench cut out of my driveway 8 inches wide and 6 feet long. I have two questions: 1- when refilling the trench with concrete do I need to use a bonding agent so the new concrete will bond to the old? 2. do I need to put a pipe around the new French drain so I don't cement right up to the plastic pipe? If I put a bigger pipe than the French drain do I need to worry about rain/snow melt getting under the slab?

Rick :

Welcome, my name is XXXXX XXXXX I will do my best to help you with your issue.

Rick :

Is the pipe under the driveway perforated?

Customer:

yes, at the lower part away from the driveway, not right under

Rick :

If the section under the driveway is not perforated then you don't need to sleeve the pipe unless it's so close to the surface that the new concrete will come in contact with it

Rick :

Using a bonding agent is a good idea

Customer:

the pipe on the horizontal part in under the gravel base. the only part that will come in contact with the cement is the part connecting to the downspout

Rick :

You can use foam pipe insulation to keep the concrete away from the pipe. I'm assuming this is a vertical penetration. If you use a larger diameter pipe then your concern about water freezing in the gap is warranted

Customer:

This is a vertical penetration. I will try the foam around the pipe

Rick :

I this case since this is only a downspout it

Rick :

It's not critical that you sleeve the pipe where it penetrates the concrete

Rick :

If this was a water line or a house hold drain which is subject to a lot of expansion and contraction then sleeving is critical

Customer:

That is good feedback...thanks

Rick :

You're welcome!

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