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Hello,
I am building a workshop extension and I am almost up to DPC level and ready to fill the cavity with lean mix concrete to ground level but a friend told me that I should have installed a Cavity Tray below the DPC with weep holes to drain any water from the cavity. There is nothing on the plans that mention this but I need to install a methane gas barrier and the installation notes for this do show the membrane being fitted to the inner leaf at DPC level with a cavity tray down to the outer leaf to just above ground level so I'm now worried that I may have to demolish several courses to fit the cavity tray and weep holes.

Any help/advice will be very welcome.

Lee Hewitt.

LEE,

PROBABLY NOT WHAT YOU WANT TO HEAR BUT AS BUILDING INSPECTOR WILL WANT TO SEE THE FOUNDATION TO DPC CONSTRUCTION BEFORE YOU CAN PROCEED WITH BUILD, YOU'LL HAVE TO BITE THE BULLET AND DEMOLISH THE OUTER SKIN TO THE LEVEL REQUIRED TO INSTALL THE CAVITY TRAY AND WEEP HOLES THROUGH MORTAR JOINTS IN RECONSTRUCTED BRICKWORK BACK TO DPC LEVEL.

HARD TO BARE BUT LEARN THE LESSON!!!

ALDA.

Many thanks for this reply. It may not be too bad as I've not gone too far up yet but I'm not sure what level the weep holes need to be fitted. Are they to be fitted in the perps at the side of the bricks level with the lean mix cavity concrete or do they go higher up towards DPC level. I was going to set the DPC level at the second course above ground level.

Many thanks again,

Lee Hewitt.

LEE,

IDEALY, THEY SHOULD BE VISIBLE (SO THEY DONT GETTED BLOCKED), SO JUST ABOVE GROUND LEVEL IS OK, PROVIDING THEY DO THEIR JOB AND DRAIN THE CAVITY.

ALDA.

LEE,

GOOGLE "CAVITY TRAY STANDARDS".

LOTS OF GOOD INFO FOR YOUR PROJECT ON SITE WITH SAME NAME!!!

CHEERS,

ALDA.

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All cavity trays and weep hole should be installed at dpc level

also again at joist level

and over all lintels

hope this helps

See the DIY Doctor projects section on cavities and lintels