Hollowcore - close ends?

Meloh

Is it worth paying extra to get ends closed on hollowcore by the manufacturer?
What is the benefit of closing them and has anyone done this?
I've read on other threads about wrapping ends with felt but would closing ends do same job?

barney150

depends what your building on top, ie block or stud. It will increase the shear strength of the slab. Check out the typical construction details on the manufactures website such as breton, and follow their recommendations

Naux

If you are pumping your cavities then I'd say it would be important to close the gaps at the ends. I've just finished doing it with expanding foam on my house. Its a bit of a pain in the arse but worth it if you intend pumping the insulation.

sinnerboy

Vermin can take up residence in the hollows mid build ..... happened on my sites more than once

soldsold

just had solid wideslab 150mm installed


150mm wideslab has an STC sound insulation rating of 53, 150mm hollowcore is 48.

I wrapped the solid slab with solitex just for good measure.

Only 1 euro in the difference in price per m2 for solid vs hollow in my case.

sydthebeat

soldsold wrote: »

just had solid wideslab 150mm installed


150mm wideslab has an STC sound insulation rating of 53, 150mm hollowcore is 48.

I wrapped the solid slab with solitex just for good measure.

Only 1 euro in the difference in price per m2 for solid vs hollow in my case.

soldsold...

had you any issues laying the slabs on the solitex in regard to tearing etc??

soldsold

No, all went well, I tacked the solitex to the wall with slating battens and weighed it down in the cavity, then put a 9 inch dpc on top of the solitex with a bed of mortar on the dpc.

The dpc and mortar bed seems to have allowed the slabs to slide ok without any signs of tearing.

The blocklayers also built the external walls up a couple of blocks before putting in the slabs, so that the crane driver would have to be extra careful dropping the slabs into position.

sas

soldsold wrote: »

The dpc and mortar bed seems to have allowed the slabs to slide ok without any signs of tearing.

This is probably a stupid question but was the mortar bed dry when the slabs arrived?

soldsold

No, I had arranged to have a blocklayer on site when the slabs arrived with a mix ready to go as they started lifting them in. DPC was already in place with bricks holding it down.

sydthebeat

soldsold wrote: »

No, all went well, I tacked the solitex to the wall with slating battens and weighed it down in the cavity, then put a 9 inch dpc on top of the solitex with a bed of mortar on the dpc.

The dpc and mortar bed seems to have allowed the slabs to slide ok without any signs of tearing.

The blocklayers also built the external walls up a couple of blocks before putting in the slabs, so that the crane driver would have to be extra careful dropping the slabs into position.

excellent... thank you...

mark2003

I wrapped the solitex with out any mortar,worked the finest.I nailled the felt to the walls to keep it in position while the slabs were laid.The outer walls where built up before the slabs were laid so the guys had to to drop the slabs straight down.The solitex felt is very dear considering you will only use 20% of the roll.200 euro a roll.

soldsold

I paid 155 a roll inc vat at the local hardware store in Birr.

sydthebeat

mark2003 wrote: »

I wrapped the solitex with out any mortar,worked the finest.I nailled the felt to the walls to keep it in position while the slabs were laid.The outer walls where built up before the slabs were laid so the guys had to to drop the slabs straight down.The solitex felt is very dear considering you will only use 20% of the roll.200 euro a roll.

you can use the remainder as part of the roofing felt..

FergusD

I presume that ideally it shouldn't just be the ends of the slabs that are wrapped?

Thanks,

Fergus.

sydthebeat

FergusD wrote: »

I presume that ideally it shouldn't just be the ends of the slabs that are wrapped?

Thanks,

Fergus.

there should be a sufficient lap that can be adhered to the blockwork over and under

FergusD

I was more thinking about the sides of the slabs, rather than just the ends?


WWALLHERE
S1 S2 S3
S1 S2 S3
WALLHERE

So wrap the ends of the slabs where they sit on the wall, but also the sides of slabs S1 and S3 if they are partially on the wall? I'm not sure if this can even happen?

sydthebeat

FergusD wrote: »

I was more thinking about the sides of the slabs, rather than just the ends?


WWALLHERE
S1 S2 S3
S1 S2 S3
WALLHERE

So wrap the ends of the slabs where they sit on the wall, but also the sides of slabs S1 and S3 if they are partially on the wall? I'm not sure if this can even happen?

Doesnt happen that often in practise. the slabs are supported at the ends. The first slab installed parallel to the wall doesnt actually sit on the wall, the wall is carried up uninterrupted beside it.

but if the side of teh slab is, for some reason, sitting on an inner leaf, the it should be wrapped too.

rok

We are due to have solid wideslab 150mm (not hollowcore) installed soon.

I presumed the slabs could just sit on the inner leaf.
Sorry fior thick question, I have overlooked the finer details of this one...

Are the mortar, Solitex + DPC necessary?

sydthebeat

rok wrote: »

We are due to have solid wideslab 150mm (not hollowcore) installed soon.

I presumed the slabs could just sit on the inner leaf.
Sorry fior thick question, I have overlooked the finer details of this one...

Are the mortar, Solitex + DPC necessary?

The 'necessity' is to achieve a required air tightness test result on completion of the dwelling, namely min 10m3/m2/hr

The wrapping of slabs ends greatly enhances the ability to achieve this level.

Otherwise retrospective work that may need to be done to achieve min level can be very, very, VERY costly.

rok

thanks once again Syd!

sydthebeat

sydthebeat wrote: »

The 'necessity' is to achieve a required air tightness test result on completion of the dwelling, namely min 10m3/m2/hr

The wrapping of slabs ends greatly enhances the ability to achieve this level.

Otherwise retrospective work that may need to be done to achieve min level can be very, very, VERY costly.

Isn't solitex breathable ? would it not have to be completely air tight ?

BryanF

Deleted User wrote: »

Isn't solitex breathable ? would it not have to be completely air tight ?

the use of the word 'breathable' in construction is misleading. think - 'Gore-tex' - something can be 'breathable' and still be air-tight;)
look here
this is a bit more comprehensive
and I'd recommend this book