Advice on building a conservatory

Discussion in 'Builders' Talk' started by rugbyjack2005, Oct 11, 2018.

  1. rugbyjack2005

    rugbyjack2005 New Member

    I'm in the process of building a conservatory myself and wanted to clear up a few questions i have.

    It is a Victorian style conservatory with a timber frame and double glazed glass. It will have 2x 14.5ft long walls that join perpendicular to my house (1 dwarf wall and the boundary wall full height) with 3x 5ft dwarf walls at the other end with 135 degree angles. I will access the conservatory from the house by taking out the window at the back of the house and knocking through the wall below.

    The footings are all dug and i have poured the foundations in and laid the hardcore element of the oversite. The plan is to build a cavity wall and put CavityTherm in the middle and 500mm polystyrene insulation in the floor. I'll lay bricks on the outside up to the damp and concrete blocks on the inside up to the damp. Above the damp will be concrete blocks on the outside, which i will render, and thermolite blocks on the inside.

    All relatively straightforward so far. I have a few questions on the damp proofing though. My plan is to put sharp sand above the hardcore, lay one large sheet of DPM (1200ga) above this and over the inside layer of bricks and then pour the concrete oversite in. I was then going to lay 1 row of bricks on the inside, lay 450mm wide DPC on this, angle it down to and over the outside brick to allow any moisture that gets through the outside bricks to run off. I'll also take out a bit of the house wall pointing and make sure the DPC is continuous and there is no bridging. I'll the lay the another layer of bricks on the outside to bring it to the same height as the inside wall, then lay concrete blocks on the outside and thermolites on the inside. Once the wall is built, i will then construct the conservatory and do the flashing. Once water tight, i will take the window out and knock through the wall. Once done, i will lay the screed (a little back to front but the only way i can make sure the floor is completely flush with the house floor as i don't want a step).

    Does this sound like a sensible plan? Do i need to lay a bit of concrete in the cavity above the foundations before adding the angled DPC - i guess it wouldn't do any harm but is it necessary as i would have hoped that it wouldn't be holding much water? Can i simply lay the CavityTherm above this or do i need to put something inbetween? Have i missed anything?

    Thanks in advance for your help.
  2. candoabitofmoststuff

    candoabitofmoststuff Active Member

    If you do that, and don't have an "external" door to the conservatory in that opening, you may find, (as I did), that it counts as an "extension". You might not need planning permission, but probably will need to meet building control regulations, particularly with regard to thermal efficiency.

    Sorry I can't help with the specifics of your question... but you might want to investigate further or you might find it comes back to bite if you ever decide to sell!

    Good luck with it all.


  3. rugbyjack2005

    rugbyjack2005 New Member

    I got approval through the neighbour consultation scheme and no, it doesn’t fall under building regs as it is under 25sqm.
  4. jonathanc

    jonathanc Active Member

    sorry it does fall under building regs

    see below in italics

    Building regulations will generally apply if you want to build an extension to your home.

    However, conservatories are normally exempt from building regulations when:

    • They are built at ground level and are less than 30 square metres in floor area.
    • The conservatory is separated from the house by external quality walls, doors or windows.
    • There should be an independent heating system with separate temperature and on/off controls.
    • Glazing and any fixed electrical installations comply with the applicable building regulations requirements (see below).
  5. rugbyjack2005

    rugbyjack2005 New Member

    Sorry it doesn’t - as per above, it’s exempt... and yes, I will be putting a door up.

    Can we get back on the topic of the actual building please!
  6. ajohn

    ajohn Active Member

    Just to try and clear the regs up as I am doing something similar at some point. Even extensions under a certain size are exempt - well mostly so. Electrics need to comply and also glass requirements. Glass mostly relating to opening doors unless it goes down to rather low levels or is used in the roof. Most would insulate to modern standards anyway.

    I asked a building inspector fairly recently. In some ways a permitted extension makes more sense than a typical conservatory because of light loss in the room a conservatory is connected to if the usual roof material is used.


Share This Page