Our house is 30 years old. The lower level is a mostly finished walk out with no signs of dampness.

The problem...the existing tile is about 1'foot below grade, covered with poly and stone.
The new drain tile will be at the footers, about 10 ft below grade.

Due to the slope of the lot the old system cannot be capped off at the new addition.

Should the existing system be replaced even if there are no issues?

This house has no gutters, most likely due to the surrounding trees. The new and existing facia should match, so does this mean no gutters on both with poly just just below grade?

This message has been edited. Last edited by: v10rick,

To comment with any intelligence would require seeing the general topography of your lot and the size and shape of the addition and existing house.

I will say that a house should have gutters. There are many systems which prevent leaves from accumulating in them.

I also don't understand why a foundation drain is covered with stone and poly. Poly what? Usually they are covered with a geotextile to try to limit the entrance of silt into the pipe. What kind of pipe is used?

If your new foundation drains will be 10 feet deep, where will they discharge? You also should backfill the 12 to 18 inches next to the foundation with gravel full height. And be sure you apply at least one and better yet, two thick brush coats of dampproofing to the foundation, and you may as well embed a sheet of polyethylene film in the dampproofing. But the new drains should be independent of the existing ones.

Richard because of the grade the new tile can discharge behind the new addition but some trenching will be required. The other option is a sump pump.

The existing system is perferated plastic pipe covered with plastic sheet and then with stone.

We will parge the wall, apply dampproofing and backfill with stone as you suggest. Since parging and dampprofing will be done as the block is laid (limited space) polyfilm will be difficult.