Hole for Crawl Space

[rqx]

Hello,
We have ergebjälklag in our newly purchased house (we do not have access yet) and want to access the crawl space. We want to get down from the inside (difficult from the outside), is it possible to make a hole anywhere? I have heard that you should at least make a hole at the seam of the erg to not cut a whole sheet. But should you reinforce in any way once you're through? And should you do it near an outer wall, by the load-bearing wall, or in the middle?
/Tim

 

[skutten11]

If there is a garderob, it's best to have the hole there, it gets a bit messy to have it in the kitchen floor

 

[justusandersson]

I would probably advise against drilling holes in an ergebjälklag. It is impossible to do so without damaging the reinforcement. Drilling from the outside is the only option, and preferably after consulting someone knowledgeable in construction engineering.

 

[rqx]

We are going to build a new wardrobe so we can have it there.

A few different opinions here, talked to an acquaintance who said it wasn't a problem to make a hole in erge?

 

[Dan_Johansson]

We're going to build a new wardrobe so we can have it there.

Different opinions here, talked to an acquaintance who said it wasn't a problem to make a hole in erge?

I think the structural engineer and the driller would give two different answers to that question...

Edit: can't you make a couple of small inspection holes and look in with a camera?

 

[rqx]

There are ventilation holes but want to fix the climate and the bathroom renovation means I have to go down there

 

[justusandersson]

Then you have to make a hole from the outside.

 

[rqx]

Then you must make a hole from the outside.

Okay, can you elaborate why?

 

[justusandersson]

One cannot make such large holes in reinforced concrete slabs without damaging their function. This is obvious to anyone with training in structural engineering.

 

[rqx]

Thanks for the answer! Do you have any idea how breakthrough slabs are usually reinforced? If you can cut at a joint and get between two reinforcement bars? Or is it more densely reinforced? What kind of company should you contact to do it and make calculations?

Edit: if you make a hole in the joint between two elements, can you then make an over-dimensioned reinforcement afterward?

And where the hole is, nothing needs to be supported, right? It is in a closet. Does that make any difference?

 

[Dan_Johansson]

Now, I have no experience with concrete slabs, just "googling like an old man." I believe that the reinforcement is dense enough that you can't make a hole big enough to fit a body without breaking the reinforcement...

Concrete has relatively poor tensile strength, and that's what the reinforcement addresses. Cutting the reinforcement creates problems for the entire "element," not just where the hole is...

 

[justusandersson]

A composite floor consists of a system with concrete beams on which prefabricated concrete cassettes have been placed. Insulation has then been laid, followed by additional cast-in-place concrete on top of the insulation. The reinforcement is quite dense, and if you start cutting, you can cause significant damage. There is no easy way to make an opening down to the crawl space. Dan_Johansson's description is accurate.

 

[rqx]

Typically, very foolish to do from the outside when the garden is small :/ However, it should be possible to reinforce from underneath with strong iron that is mounted across the cassettes to strengthen?

 

[justusandersson]

Theoretically, you can of course break up the overconcrete and get access to lift up an entire floor cassette. Then you need to know where the beams are that the cassette rests on. It can also result in a very large hole that can end up anywhere without regard to the floor plan and give rise to secondary effects. Additionally, it is likely to be quite expensive. If you have access to good drawings that also show the floor construction, you can see if there are reasonable conditions.

 

[rqx]

Would it be better to take up an entire cassette than to make a hole in one, how does that make sense? I hope to get drawings when we move in but don't have high expectations.