I'm planning a living room addition with a new basement underneth it. The problem is my exsisting house is a concrete slab. I'm planning on digging the basement about 5 feet away from the exsisting concrete slab and connecting it with either another concrete slab or crawl space between the exsisting house and new addition. My question are.
1. There is no way possible to run an exterior French drain to daylight.
2. I'm planning on having a sump pump inside the basement.
3. Do you run the exterior French drain under the footing back into the basement sump pump?
4. I'm planning on using your methods, but without being able to run the French drain to daylight what do you suggest?

I'm not LW, but please, enlist the aid of a good architect to help you with the design of your new foundation. You've got a tricky problem there.

well, WATERPROOF the exterior walls of this
basement-addition, backfill w/gravel-peastone.

you may indeed want to hire, as Richard says, a 'good' architect to help you.

you may want to get some soil-tests beforehand

when using equipment next to-near existing structures, remember..'sometimes' the weight of this equipement 'could' cause crack(s)/shifting/some movement to a slab/wall etc etc....simply saying it 'could', NOT saying it will.

most likely will be X-amount of settling of soil afterwards so, heads up there. Footings,reinforcing rod etc is important, as is what is backfilled against new walls.

if you find out the soil is very saturated(not because of recent rains, always/everyday like muck, like lava, below ground) you may need 2 very good sumps w/back-up power, depends on size of addition.

because you apparently cannot run water/tile to 'daylight' doesn`t necessarily mean your going to have any problems/leaks. You could run it to sump(s) but that 'could' cause settling and/or a wash-out in TIME under the floor, under the footing(s) of addition.

have seen quite a few additions that did not have tiles run to daylight/away, they had no problems,settling, not saying YOU will or won`t just sharing what we`ve seen. Reason we were there was because....lolol, builder didn`t WATERPROOF the outside of walls, most always this is a mistake.

don`t think inside systems can`t/won`t undermine a footing(s), don`t think they`ll never cause any problems to support structure,or part of bsmt floor settling cause they can....and,(yawn) they don`t stop water from entering is the first place, most HO`s problems are on outside, not inside.

some homes are built in tough areas, on crap soil, on springs, some where they shouldn`t be so, some people who buy these homes are unfortunately kinda limited on things they can try/do, some have to LIVE with the consequences of buying these sorts of homes, sorry.

Oh, one more thing for now, the more often-harder those sump pumps have to run the shorter the life span...so to speak. Most warranties are 1 year or so, just a heads up.

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

So if you can't run an exterior French Drain to daylight, you would not recommend installing one? Or can you attach it to an interior sump pump?

I have a friend that had buit 5,000-15,000 homes and never had a problem because he over-did the water control. - These were basic homes and not high-buck (split entry ranch, 3 or 4 level splits). All had the same system.

He installed both interior and exterior drain tile in all homes and tied them together under the slab. He used only block foundations and put drain pipe from the cores into the rock around the inside tile. He also used a special block for the first course of block that held the plastic core drains and kept the drainage path on the slab open and could not be clogged during construction by debris or kids dumping dirt in the cores at night. Parged and applied waterproofing to the exterior side of the walls. Coated the interior of the walls with Thoroseal. Usually, one sump inside unless dailight drains wer possible.

In areas with fluctuating water tables, he put 1 or 2 lines of drain tile under the floors to save the basement slab from the hydrostatic pressure.

The big selling point was finished basements or waterproof basement ready to be finished by the future owners. - He made his money by doing the construction right, so he never had to be the cheapest to be successful.

There is no best way, but there are a lot of good methods and techniques depending on the goal and situation.