Cavity tray

[Pocster]

Hey all

 

im confused by these 

so they go in my outer leaf with 'weep' plugs either side so moisture can escape .

why have I never seen these on a build before ?

also if you render externally going to be very easy to block them even if you cover them .

anyone else been 'told' to use them ?

 

cheers 

[Brickie]

Okay,a cavity tray will go from your inner leaf down to the outer leaf,with weep vents @900mm or 450mm centres as per spec. For rendered work they should be sat proud of the blockwork to the depth of the render (say 20mm,if 2 coat sand & cement) so they sit flush with the finish render. They are a common detail on cavity work,principally over lintels but also at g/f level if spec'd & also at any parapets or where adjacent structures abut (I.e. Garage roof.)

Your TF supplier should supply you with a technical sheet showing how to install. 

[Pocster]

Thanks 

it's been suggested I put trays the entire length of the block work below dpc . Not just around window details etc .

[Brickie]

Why below Dpc? Who has suggested this?

[Temp]

As I understand it cavity trays are intended to catch any water running down the inside of the outer leaf and divert it to the outside. The source of this water is rain penetrating the outer leaf (bricks are porous). However I though render was meant to be a waterproof barrier so do you need cavity trays at all if the outer leaf is rendered?

 

 

 

 

[Temp]

OK Google says with render you still need cavity trays but might not need weep holes...

 

https://www.labcwarranty.co.uk/technical-library/weep-holes-in-rendered-cavity-walls/

 

 

[Pocster]

13 hours ago, Brickie said:

Why below Dpc? Who has suggested this?

Architect !!!

 

but yes it confuses me why when you have render like k rend or similar 

Edited April 23, 2017 by pocster

[nod]

32 minutes ago, pocster said:

Architect !!!

 

but yes it confuses me why when you have render like k rend or similar 

Unlikely to get water soaking through K rend But you still need trays above all openings

With at least a couple of weeps on each

 

Ive just fully K rendered mine I set the weeps at 15 mil and rendered over them

When I rubbed up  the render the following morning the weeps reappeared

I set all the weeps right above the heads and 150 out with a central weep for larger openings So I new were they were

You really don't get much render going inside the weep I jus poke a fine nail in to clean them out The L shaped type are best for render as you are left with only 10 mil showing

[Brickie]

Have you got a drawing from the architect?

[Pocster]

8 hours ago, Brickie said:

Have you got a drawing from the architect?

Now you are joking !

 

Nope!.

Edited April 24, 2017 by pocster

[Brickie]

3 hours ago, pocster said:

Now you are joking !

 

Nope!.

Ok,so where does it say you need a Dpc tray below Dpc?

The standard detail when I did them was a tray lapping down to Dpc level ( saves you using 100mm damp too,if you get it right.)

 

[Pocster]

Just now, Brickie said:

Ok,so where does it say you need a Dpc tray below Dpc?

The standard detail when I did them was a tray lapping down to Dpc level ( saves you using 100mm damp too,if you get it right.)

 

Lol

it doesn't ! . The architect visited the site and just said so .

i get the impression everyone else gets every detail defined - I don't ! :-/