dwarf wall

[dada]

am building a conservatory with about 6 bricks above dps. below dpc is 5 bricks, 2 of which will be above ground level.
now, i have brought some weephole vents, the plastic vertical ones that go between the bricks.. questio is, where below the dpc do i put them? obviously can only be in the top 2 layers of the wall above ground level, but which should it be?
also, should i fill the cavity with a sandwich (i believe its called) of cement and taper it towards the exterior wall so water can get out? if so, the weepholes will no doubt need to match that level.
tahnks

 

[Alastairreid]

read this.

www.diydoctor.org.uk/projects/cavities,cavity trays, lintels and ins...

 

[noseall]

no need for weep vents unless you are constructing a continuous dpc/dpm, i.e. as in a gas membrane.

fill the cavity with lean mix concrete up to within 225mm of the dpc.

 

[dada]

noseall - thanks - forgive my ignorance, but what is a gas membrain? also by lean, what mixture of sand/cement would youy recommend?
alastairreid - thanks - but the link is borken. could u resend plse
cheers

 

[noseall]

in certain areas like mining districts, there can be a build-up of gasses, methane, radon, etc. a gas membrane is used instead of a regular polythene dpm, prior to laying the oversite insulation and concrete.

this gas membrane is meant to keep out unwanted gasses as well as the damp. it is therefore vital that the dpm in this instance bridges the cavity and is lapped onto the external masonry also.

this in turn creates the need for a cavity tray and weep vents directly above this breach.

a lean mix concrete would be, say, 8 parts ballast to one cement (plus water).