Which empty conduits are under a precast concrete garage with strip foundation

Hello everyone,

Soon our precast concrete garage will be placed directly next to the house. We have already planned a floor opening there so that an electrical distribution box for the garden power can be installed in the garage. Besides the power cable, other cables such as network cables will also be laid. All cables come as underground cables from the multi-utility duct.

The strip foundation has already been built. The contracted subcontractor has laid DN110 KG pipes through 3 foundations and cut them flush. In the last foundation, DN75 HT pipe was laid with a slight protrusion. To make matters worse, the distances to the edge of the garage vary by up to 10 cm.

What should I do to be able to pull cables as easily as possible afterwards and to prevent the pipes in the foundations from clogging?

1) Run an 80 mm slotted (so no water accumulates) flexible drainage pipe all the way through and tie it tightly with cable ties at the HT pipe? I would only bury the pipes minimally so that they lie stably? Or will it be impossible to pull the cables through the pipes later?

2) DN110 KG pipe. Since the passage in the foundations is cut flush, I cannot connect them with couplings. Can they be connected in some other way? Butt joint and then secure against slipping with a bit of mortar?

3) DN75 HT pipes? Of course, that means losing diameter immediately and having to work with elbows and calculate carefully beforehand.

Or is there an easier way? Overall, it is only 9 meters, which are relatively straight but not completely. Since everything lies under the garage, the load from forces is also manageable.

Many thanks for ideas and experience reports

I haven't quite understood the situation yet. Pictures are always very helpful in these cases. It's always difficult to add something later when there are already cables inside. I would simply pull in additional spare cables now and run everything at once or as a bundle.

I didn't quite understand the situation. Pictures are always very helpful. Pulling something through later is always difficult in such cases when there are already cables inside. I would now simply pull in additional reserve cables and pull everything through at once or as a bundle.

Hi, thanks for your answer. The situation is as follows. The strip foundation is in place and before the garage is built, I want to prepare everything as best as possible. An electrical distribution box is going to be installed in the garage. The cables come from the basement and are routed through the front two foundations and then through the garage floor to the distribution box. Next year, as part of the garden work, power cables should again be routed from the distribution box under the garage through the front and rear foundations into the garden.

The landscaper who built the foundations poured various empty conduits into the foundations. Since these can become clogged between the strips, I thought about connecting the sections before the garage delivery, so that it will be easier to pull cables later. For this, I had outlined the above-mentioned options.

1) Flexible drainage pipe without connectors but corrugated. 2) With KG pipes and elbows. Smooth. Unfortunately, the KG pipes have to be connected butt joint at the foundations somehow, since I do not have an overlap for a sleeve. 3) HT pipes DN75, since that is the smallest pipe in the 4th foundation and protrudes. Then I could lead it "seamlessly" through the other holes. In the middle, then a 45-degree elbow so that the pipes can be directed into the garage.

Attached is a graphic

Hmm, what diameter does the drainage pipe have then? With pipe-in-pipe you just have an edge or, even worse, the connection moves. Basically, 45-degree bends are not recommended. I would take a maximum of 30 degrees. How do you get through the floor of the garage, is it a concrete slab?

The purpose of the multi-compartment is to enable a water- and gas-tight house entry. This also concerns the passage of your multitude of cables, not only through the foundation as well as the floor slab or basement wall but also at the exit of the passage, that is, each individual cable with sealing. If the gas supply is introduced through the multi-compartment, it certainly hits the mark.

Hmm, what diameter does the drainage pipe have then? Pipe in pipe, you just get a ridge or, even worse, the connection moves. In principle, 45-degree bends are not recommended. I would take a maximum of 30 degrees. How do you get through the garage floor, is it a concrete slab?

At the hardware store, there are DN80 and DN100 drainage pipes, closed and slotted. I would test the 100 first and otherwise go for the 80. Slotted, since I am laying underground cables anyway. The prefabricated concrete garage stands on the foundations, and there is a 10x10 cm opening configured in the floor slab.