Phil MCavity...

[Ellwood]

Hi all, I am sure I have seen similar posts about this on here before, but I can't find them again, so apologies for repeating this again.

I am building an attached garage and utility room, with a 100 mm cavity wall. The outer leaf is in brick, the inner in block.

I am now ready to start building up from floor level but am not sure how to finish the cavity before I begin.

1. I understand I should fill the bottom of the cavity with a sand and cement mix, but to what level, and what mix ratio?
2. This sand and cement mix should slope downwards to the outer leaf, but by how much?
3. I will be using a 50 mm Kingspan or similar insulation, how far down the cavity should this extend - to DPC level, or right down to the sand cement mix mentioned above?
4. Should I put weep vents in the bottom of the cavity (at ground level)? I know this is a contentious subject amongst some of you but I thought I should ask all the same!

Any pics/diagrams of the above would be appreciated.

Many thanks in advance for your replies,

Ellwood

 

[noseall]

The wall cavity below dpc should be filled with lean mix concrete to within 150mm of the dpc.

Form a crude slope - in other words make sure it does not slope towards the internal wall. This can be done with a shovel!

You can either insulate the cavity below dpc or run perimeter insulation around the external walls of the 'build' when laying the oversite concrete.


No need for weep vents unless you are designing an unusual dpc detail that requires it, i.e. a gas membrane detail.

 

[Ellwood]

Thanks Noseall.

 

[penguinman]

Noseall
Your comment to the last guy was very good so IO hope you can help me too.

I am building a cavity wall with 100mm full fill insulation. Bearing in mind that twist wall ties have to be inserted around openings at max 300mm spacings around openings, I presume that it is best to build both skins at the same time to make sure the ties matchup?
This means a wall tie at each block height.

Is it best to cut the wall batt insulation into rectangles to match the wall tie locations?

If you have a door opening within 1 brick of the wall return, do you still need a wall tie in this single brick, or does the fact that the wall return is tied at right angles assist this section.

Apologies for all of the questions, but I would be grateful of any tips

Thanks

penguinman

 

[noseall]

We just tend to slit the inso' when dealing with wall ties that are 'out of course', then feed it around the tie.

The single brick panel or return will benefit from both tying into its opposing leaf and into the adjacent wall.

You will appreciate this when the door slams!

We always build the brickwork up to lintel height, then the blockwork, regardless of whether the ties are out of sync. In cases of 73mm imperial bricks verses metric brickwork, then you simply measure where the ties should correspond with the block courses and fit them to the nearest (low) brick. Then it is usually a case of bending the tie wire down to suit.