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9" cavity wall

  • 18-02-2011 3:51pm
    #1
    Andrew33
    Closed Accounts Posts: 1,857 ✭✭✭


    I need to replace a 4" cavity wall (party wall in yard) with a 9" cavity wall which will support a conservatory eventually. The 4" wall is built directly on the concrete slab which forms the yard. This wall has stood for 16 yrs without movement or cracking so I'm assuming the concrete slab is pretty stable.
    Question is, do I need to break tru this slab and dig proper foundations for the new wall or can I simply build the 9" wall directly on the slab?
    I'm thinking the new wall will be in the region of 2 to 3 times the weight of the existing wall as it will be higher also.
    Also, do I need planning permission for the new wall?


Comments

  • #2
    ART6
    Registered Users, Registered Users 2 Posts: 2,632 ✭✭✭ART6


    Andrew33 wrote: »
    I need to replace a 4" cavity wall (party wall in yard) with a 9" cavity wall which will support a conservatory eventually. The 4" wall is built directly on the concrete slab which forms the yard. This wall has stood for 16 yrs without movement or cracking so I'm assuming the concrete slab is pretty stable.
    Question is, do I need to break tru this slab and dig proper foundations for the new wall or can I simply build the 9" wall directly on the slab?
    I'm thinking the new wall will be in the region of 2 to 3 times the weight of the existing wall as it will be higher also.
    Also, do I need planning permission for the new wall?

    If you're going to build a conservatory on the new wall, I assume the wall will be no more than waist height? If so, I did exactly that three years ago on a concrete patio outside my house. The patio was pretty ratty TBH, but a quick check showed that it was cast on rubble and was about 50 mm thick, so I just went ahead and built my wall. I have not had any problems so I wouldn't think you would have either.

    Where planning permission is concerned, I didn't ask the council. I live way out in the sticks with my nearest neighbour 200 yards away behind a high hedge, so I didn't see the need to ask the council's permission! Anyway, as I understand it, you can build something without PP as long as it is less that 40 square metres in floor area?


  • #3
    Antiquo
    Registered Users Posts: 290 ✭✭Antiquo


    If you want to build a consevatory larger than 25m2 you'll need planning.

    As for building the wall and conservatory best remove the existing slab completely for the entire area of the proposed conservatory.
    Put in proper foundations for the new wall with DPC and build up floor with hardcore, blind, DPC, insulation and cement ,etc. If you build onto the existing slab it could move. Also putting in a proper floor will prevent damp issues.


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