Holey HCF Batman!

[MortarThePoint]

I have some holes in the HCF for the shower waste pipe to pass through. I held back the screed a bit around the holes for obvious but potentially comedy reasons. This leaves me with a challenge supporting the shower tray corner as the HCF holes are large (min. 200mm per side).

 

Bridging over the hole with a lintel would be nice, but the screed is only about 55-60mm deep. What have other HCFers done here?

 

Where there is just a gap due to no screed, I figure I can just build up level with cut blocks and mortar.

[MortarThePoint]

Another larger hole

Edited October 9, 2023 by MortarThePoint

[Mr Punter]

What is HCF?  Not something I have heard of.

[Galileo]

Concerete slabs with holes, horizontal not the vertical ones in the picture.

 

https://www.milbank.co.uk/products/flooring/hollowcore/

[Mr Punter]

12 minutes ago, Galileo said:

Concerete slabs with holes, horizontal not the vertical ones in the picture.

 

https://www.milbank.co.uk/products/flooring/hollowcore/

 

Ah, right.  I have used this before but never heard it called HCF.

 

With the holes you can hold some ply underneath with an acro and fill in with some concrete.

[Conor]

Did you check that size of opening was OK with the SE/supplier? Have you cut through one or two cables?

 

For mine, once services through, I cut a piece of ply to suit, fixed battens to the sides of the slabs so ply was level with slabs. Bit of foam or cement to seal it off. You'll need to make the rest of the levels up with insualtion and a bit of cement + self leveller.

 

[MortarThePoint]

3 hours ago, Conor said:

Did you check that size of opening was OK with the SE/supplier? Have you cut through one or two cables?

 

For mine, once services through, I cut a piece of ply to suit, fixed battens to the sides of the slabs so ply was level with slabs. Bit of foam or cement to seal it off. You'll need to make the rest of the levels up with insualtion and a bit of cement + self leveller.

 

 

All the holes are 'from factory' so sanctioned by the HCF designer. The holes are quite large because of their minimum sized hole (200mm X 200mm) and in one case uncertainty as to final shower tray size. Annoyingly, for that larger one, I'm not even using the hole anymore.

 

Sounds like you described sealing the hole accoustically, but I'm more worried about structural support of the shower tray

[Conor]

50 minutes ago, MortarThePoint said:

 

All the holes are 'from factory' so sanctioned by the HCF designer. The holes are quite large because of their minimum sized hole (200mm X 200mm) and in one case uncertainty as to final shower tray size. Annoyingly, for that larger one, I'm not even using the hole anymore.

 

Sounds like you described sealing the hole accoustically, but I'm more worried about structural support of the shower tray

In that case, shutter from below with ply, dowel in to the slab, and then fill with concrete.

 

I regret not getting my openings done in the factoy, so much harder afterwords!

Edited October 9, 2023 by Conor

[MortarThePoint]

28 minutes ago, Conor said:

In that case, shutter from below with ply, dowel in to the slab, and then fill with concrete.

 

I regret not getting my openings done in the factoy, so much harder afterwords!

 

Do you add some mesh or something? Does that just rely on the jagged edge of the hole to grip the concrete? Wouldn't want it to fall through the hole 🤣

[Conor]

Th bit I had to fill in was long and narrow, just ran a couple lengths of rebar along the length. Tbh a few 300mm dowels or threaded rod drilled in to the edges of the slab will be enough.