hollowcore slabs

cavanmann

hi

Building new house this year and going to use hollowcore slabs.was at a show recently and was told by a guy who does air tight testing that i should cap the end of the slabs. has anyone heard of this before?

Thanks

FesterBeatty

Why? The edge screed detail will cover this anyway. And if you're thinking of proceeding without a structural screed be aware that you will not meet the peripheral tie requirements of the buildings regs and Irish/British standards - its something a LOT of people miss out on

cavanmann

I BELIEVE TO STOP AIR PASSING FROM CAVITY (WALL ) IN TO DROPPED CEILING AREA

Mellor

The "cores" don't connect to the ceiling area. Besides as mentinoed above, a structural screed will block off the cores anyway.

sas

Hi OP,

I believe what the airtightness guy is talking about is what has been discussed here several times. It's often referred to as a hollow core wrap.

In this thread it was discussed and the posts I made are still 100% valid today.

http://www.boards.ie/vbulletin/showthread.php?t=2055337642

I had this done on my own house. It's time consuming but I hope it will prove worth the effort.

SAS

peterc14

You could ask you hollowcore provider to fill the ends of the slab... I have seen this done before.

sas

peterc14 wrote: »

You could ask you hollowcore provider to fill the ends of the slab... I have seen this done before.

You could but you'd be wasting your time. Mine came with the ends sealed and I still did the wrap.

The issue is not air\through the slabs.

The issue is air moving around\between the slabs.

The membrane wrap is the best way to achieve this.

about2build

Can you describe this procedure a bit more sas...just trying to visualise it here:eek:

L driver

Hello,
sas is right. Where the hc sits on the internal leaf, assuming cavity build, there is a break to the cavity, so therefore this has to be incorporated into the the air tightness envelope. This can be done by putting a membrane in place before slabs are dropped. Leaving a block out on the top row of internal walls, where the internal wall meets the internal leaf of the cavity wall can prove helpful for this. But it is tricky work. This membrane has to be returned on top ofthe hc for the internal leaf to be built on. Also get the ends of all the cores sealed. Also plaster down from bottom of hc to below line of ceiling before putting mf ceiling in place, cos blocks are porous. hope this helps.

sas

about2build wrote: »

Can you describe this procedure a bit more sas...just trying to visualise it here:eek:

Do the pics here make it any clearer?

http://www.boards.ie/vbulletin/showpost.php?p=66007753&postcount=856

about2build

Thanks sas ya that helps a lot.so its just to seal the junction point really...is the membrane then lapped in and plastered on top of or would it be cut back ??

sas

about2build wrote: »

Thanks sas ya that helps a lot.so its just to seal the junction point really...is the membrane then lapped in and plastered on top of or would it be cut back ??

It seals all of it. It prevents air passing through, above, below or between teh hollowcore slabs.

The membrane should be meshed onto the block work upstairs. This is done where where the upstairs skirting will eventually be fixed. You use expanded metal.