Cavity wall

[c9656750]

All

my builder is about to start building up the walls on my extension, it going to be block/block with 100mm cavity.

question is this, what is "normal" construction fo these walls - solid concrete blocks, or thermalite or similar, and what insulation goes in?

a load of 100mm concrete blocks has arrived, along with what looks like sheets of fibreglass type insulation?

just want to confirm we are meeting latest 0.3u regs.....

its a double storey side extension....

 

[^woody^]

The builder should use whatever is specified on the plans

 

[c9656750]

Does 100mm block / 100 cavity / 100 block meet 0.3u build regs - assuming solid blocks.

 

[freddiemercurystwin]

You need to tell us the make/specification of the blocks/insulation the builder is proposing, then we can tell you if it complies or not. There are dozens of different suppliers for both insul and the blocks and hundreds of combinations. However generally the 100/100/100 wall is the norm.

 

[c9656750]

The blocks are, according to delivery note, plasmor fibolite standard solid, 3.5N, these ok?

 

[freddiemercurystwin]

Depends on the insulation, tell us what that is?

 

[c9656750]

Isover cavity wall system 100mm ?????

 

[DevilDamo]

just want to confirm we are meeting latest 0.3u regs.....

That doesn't make sense. You're either complying with the latest regs or you're looking at achieving 0.3. The latest regs ask for a u-value of 0.28.

 

[c9656750]

steady on, i'm no professional - thats why i'm here

i presumed (wrongly i now see) that 0.3 was the latest spec - i have checked to specs submitted to BC and they say 0.3, so does this lot meet 0.3?

 

[DevilDamo]

The new Part L came into force on 1st October 2010. If your BR application was deposited and registered before that date, then your proposals will come under the old(er) Part L, which asks for a u-value of 0.3. If the BR application was deposited and registered on/after 1st October then your proposals will come under the new(er) Part L, which asks for a u-value of 0.28.

 

[c9656750]

it was deposited before 1st oct
does the 100 block /100 cavity /100 block as detailed above meet 0.3u ?then

 

[DevilDamo]

As it has been mentioned already, what is noted on the drawings and what has been approved?

Why is the proposed cavity wall comprised block, cavity, block? Is it a rendered wall? That cavity wall width can achieve a u-value of 0.3, depending on what insulation is used, which has also been mentioned above.

 

[c9656750]

seriously, will someone just answer the question

does a 100mm block / 100mm cavity/ 100mm block wall meet a 0.3u thermal value?

the blocks are plasmor fibolite standard solid, 3.5N (as previously stated)
the insulation is Isover cavity wall system 100mm (as previously stated)

yes the wall will be rendered on the outside, not sure how this is relevant though, as no insualation will go into that.

a yes or no will do, thanks in advance

 

[garyo]

Take a look at page 6 of this LABC guidance PDF : http://www.derrycity.gov.uk/buildingcontrol/downloads/Herts U Values.pdf

...and you'll see why there are so many questions. Even your interior surface finish is a factor.

You blocks have a K value of 0.25 (see page 9) so according to the table on page 6, your wall is over specified - you could get away with an 85mm cavity.

Gary

 

[c9656750]

thats great, all i need to know