Fitting the cavity insulation

[trevorbayliss]

Right thanks for this. So when you mean over sailing, does this mean you set your brick course back say 10mm off the base i have created ? In my photo you can see the exterior leaf is at the finished external ground floor level (patio will be level with this course of brick). I thought it would be best to do this course in my facing brick in case any was showing, but it should all be hidden really.

So my next course up will be the start of the seen external leaf.

My front section is actually 80mm wide tapering down to 70mm, so i am planning on knocking this course out and redoing it at the correct width. I have actually gone inwards a lot more than the other 2 walls and it is all down to the conservatory foundation putting me off line. I can actually see where i have moved inwards quite a bit at the far end.

So to bring the wall out by 30mm i think i will just take out that first course of facing brick and build up off the foundation to give me a good base. This way i can accommodate the extra thickness of my brick as well. I have made the building 100mm shorter than planning just in case of a cock up.

 

[noseall]

Interesting that the cavity gets bigger the higher you go. I wonder why this is ?

Because brickies are lazy.

You can nudge the blockwork back the higher you go by going around with your level and a straight edge, before the mortar grips. The insulation likes expanding and gives the block-work a push.

 

[trevorbayliss]

Spoke to knauf this morning and my wall with 100mm cavity would only get 0.3 u value, which i am not that happy with.

He also said not to use the 100mm in a narrower cavity so i must use 85mm. So i will do this plus add the 25mm kingpin inside. This will give me a u-value of 0.28. I can use the 100mm in my front wall as i can change this around.

 

[^woody^]

Won't the 0.3 u-value depend on what blocks you are using?

There would not seem to be much practical advantage in a 0.02 u-value difference in context of the cost, palver and loss of internal room. And if this is a kitchen, wont the walls mostly be covered in units anyway?

 

[trevorbayliss]

Its a lounge and utility, so 2 rooms. If i use 25 celotex internally then i get down to 0.28, maybe lower if i use 100mm on the front wall which i intend on changing to fit. If i go with 30mm celotex then i can get it down to 0.26 u value.

I am using a standard heavy breeze block 7kn. Just thought this was what i needed to carry my 4 purlins in oak for the roof. I probably could have used a better insulated block, but i am doing this extension pretty much myself and my architect let me down with zero specification. I had to pay extra for it and was told only after i paid for the drawings. So i thought i should be able to negotiate my way through all the requirements with insulation etc myself. Generally done fine, but maybe this spec would have changed if i had some better input.

The internal space lost in the lounge would be 40mm approx on the left side and the same in the utility on the right side. This isn't too bad as making quite a bit more space for ourselves.