block / block with full cavity

[LSB]

I need help 🙂

We are building block / block with render / cladding but are struggling with weep vents and cavity insulation positioning.

 

Our SE drawings just say 150 full cavities, simple enough, but then I've looked at loads of books, websites, diagrams, spoken to arch & BC and they all vary on where the weep vents go and where the insulation starts and if we even need weep vents.

 

Our founds are 1000 deep with 850 poured concrete.  Then below the DPM there will be 1 block on its side, so 110 high (incl mortar) and 1 block std layout, 225 high (incl mortar) totalling 335 incl mortar.

So, this equates to 150 below FGL with 185 above FGL to allow for the min of 150.

 

This equates to mortar (10), side block (100), mortar (10) plus 30 of the lowest cavity blocks below FGL leaving the 185 above ground up to the DPM.

 

This is all pretty straightforward except;

 

Does the insulation go right to the bottom of the cavity with 30 'underground' and 185 below DPM or does it start at the DPM (or somewhere else completely).  If this is the case then do we need to put a thin mix of concrete in this cavity.

I asked the architect who said it up to us or BC.  Surely this will have the potential to get damp and rise up, BC not replied yet.

Obviously the DPM doesn't go across the cavity so there would be nothing to stop moisture going up and up.

 

The weep hole, the arch said at 'base' level, so I asked where that is and they said FGL, but surely if there is a puddle or heavy rain / wind combination it would enter the cavity in through the vent rather than exit.

The render / cladding won't be going to ground level so weep vents will be fine at FGL, but if they are higher then won't that allow damp to sit below the vent and if insul is at the bottom just make that damp.

 

Insulation is mineral wool, which raises the question if this starts at DPM and, supposedly, doesn't need fixing then why won't it just fall down to the bottom of the cavity.

 

I am getting so much conflicting information that I am hoping that this place will have a more definitive answer for me.

 

TIA

Jill

 

[Declan52]

Weep vents are designed to let moisture out not in by the way the fins are angled. Some will always make it through but won't cause any issues so put them at wherever the architect wants them to go. He should have positions indicated on your drawings???

If you imagine the bottom of your floor insulation as the base then your cavity insulation should start at this level so you have a continuous layer from the floor right through to the cavity and then this goes up to where it meets the roof insulation to form an envelope around the house.

You will have wall ties that hold both block skins together and the very bottom row is what you first layer of insulation rests on.

 

 

[LSB]

5 minutes ago, Declan52 said:

Weep vents are designed to let moisture out not in by the way the fins are angled. Some will always make it through but won't cause any issues so put them at wherever the architect wants them to go. He should have positions indicated on your drawings???

If you imagine the bottom of your floor insulation as the base then your cavity insulation should start at this level so you have a continuous layer from the floor right through to the cavity and then this goes up to where it meets the roof insulation to form an envelope around the house.

You will have wall ties that hold both block skins together and the very bottom row is what you first layer of insulation rests on.

 

 

arch just says 'base' level and doesn't show them on the drawing focusing on the insulation.

thanks for the prompt reply

 

[Iceverge]

26 minutes ago, LSB said:

Our founds are 1000 deep with 850 poured concrete.  Then below the DPM there will be 1 block on its side, so 110 high (incl mortar) and 1 block std layout, 225 high (incl mortar) totalling 335 incl mortar.

So, this equates to 150 below FGL with 185 above FGL to allow for the min of 150.

 

This equates to mortar (10), side block (100), mortar (10) plus 30 of the lowest cavity blocks below FGL leaving the 185 above ground up to the DPM.

 

 

I'm not 100% following this. Any chance of a sketch?

 

A couple of strategically places pieces of EPS could really reduce any thermal bridging at the wall floor junction.  

[LSB]

11 minutes ago, Iceverge said:

 

 

I'm not 100% following this. Any chance of a sketch?

 

A couple of strategically places pieces of EPS could really reduce any thermal bridging at the wall floor junction.  

I have the drawing on paper, will dig out the phone to take picture and post.