block built shed water ingress

[cornishsteve333]

Hi all I have a damp issue with my block built shed

in a space at the bottom of my garden I have a block retaining wall 1m high. it is 1 block longways wide built on concrete footings with a purforated drain pipe in behind.

I decided to build a block shed building of the retaining wall for 2 sides of the shed.

So I:

• had the floor concreted (4inch thick)
• built the walls of the shed using blocks on there edge
  
• fitted a fiber glass roof, clad walls with larch, fit doors, insulated the roof etc.
• tanked interior walls using kb to 1m (following the instructions).
• there was a considerable ammount of condensation but I was happy the wall was water. tight so I rendered using waterproofer in the render.

after a week and happy it was dry I started to paint the interior then this morning I woke to find water penetration in multiple locations.

So it appears the tanking has failed.

can anybody suggest any ways I could fix this without removeing all of the render and re tanking.

 

[John D v2.0]

Not sure how tanking works on the inside of a wall, presumably the drainage is supposed to keep the water at bay? but how about building a drained cavity and then having a dry inside leaf? Then there won't be any water pressure on your internal wall coverings.

 

[^woody^]

I'm struggling to visualise the tanking and the rendering, with the new and retaining walls and where the failure is. It might not have been a good idea to tank and render.

 

[cornishsteve333]

Hi woody, so the block walls make up the 1st metre of 2 of the walls then using wall ties I built the other 2 walls from the base of the concrete pad, it is at this height where the issue is (although I have built another 1m on all 4 sides).

I then preped and tanked the interior on all 4 sides, and then rendered ontop of the tanking.

the failures are in a few places in that 0-1m section