Type E Cavity tray questions

[allywag]

Hi there,
I need to install some type e cavity trays (http://www.cavitytrays.co.uk/pdf/23-Type-E.pdf) above an extension on my property. Builder didn't install (don't ask) and now the wall inside is wet.

Untitled

• allywag
• 20 Feb 2014
• 1

Untitled

• allywag
• 20 Feb 2014
• 1

A few questions:

1. Should the lead flashing be higher (two courses above the roof)? Ideally I won't have to redo this.
2. How close to the window do I go with the trays?
3. How far past the vertical line of the right-hand extension wall do I need to take the trays? I assume there is some sideways absorption of moisture so I'm guessing stopping directly above is not enough.

Many thanks,
Alex.

 

[tony1851]

Are you sure you need to install a tray?

If you have had a breakthrough downstairs to open the rooms to the new extension, sometimes small cracks will form in the brickwork above when the steel beams are installed. Water will then find its way into these cracks and trickle down the inner face of the outer skin.

Alternatively, if the brickwork above were to be well-pointed, you would not have a water ingress problem.

It is difficult to retro-fit an effective cavity tray.

 

[allywag]

Hi Tony,

Thanks for the swift reply. Thinking about it, the pointing does need some work. But aren't the bricks themselves porous? So would pointing make any difference?

If I only needed to do the pointing, the job would be much easier!

Cheers, Alex

 

[cotswoldbuilders]

The flashing would be better fixed into the next course up, directly under the window.
It looks a bit flat set where it is, re-do the joint with lead mate ( mastic )

 

[tony1851]

But aren't the bricks themselves porous?

Yes, they are common bricks and will be slightly porous, but not to the extent that water would leak down the inside. Any leakage will be through cracks in the joints.
It would be better to re-point the wall thoroughly and see if that does the trick first, rather than jump into a cavity tray.