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Groundwork & Foundations
Foundations for a 3.3 x 2.2 metre conservatory
Anonymous user 23 February 2024 - 3.20 PM
Looking to build a foundation on the side of my kitchen, the kitchen protrudes from the front of the house and id like to have the conservatory level with the front of the kitchen and the side not encroaching in the 1 meter from boundary limit for no planning permission requirement. Height will be about 2.2 meters and Id like to have a dwarf wall a couple of blocks high.
My question is what width and depth foundations will I need? what grade of concrete? do i just tip concrete in the hole or do I add hardcore to the bottom of the trench, complete beginner with this sort of thing so apologies for asking the most basic questions.
Do I need to attach these foundations or above ground blocks to the house walls?
Do I need damp course and if so how is this added?
Also what thickness of floor should I be aiming for and should I be doing anything special with that?
Thanks in advance
Are you a tradesperson and able to answer this question?
First of all you would be looking to dig the trench down to existing foundations. As long as the ground you dig down to is sound ground, Typical strip founds would be 200mm thick with 1 layer of A393 steel mesh with a width of 600mm dig and steel mesh cut at 450mm. For starching the foundations and walls I myself would dowel the existing found at 300mm centres and the Brickie will use starter packs for securing under build walls. The bricklayers also will instruct on where to add the damp course. For the concrete floor, I would speak with your local NHBC Officer on what spec you will need.
Hope this has helped you out a little
In regards to your floor thickness question. There's quite a lot of detail involved in a proper slab. Your finished concrete slab would be prob around 6" depth, but this is poured on top of foil backed insulation again around 5" thick which is then on top of quality damp proof membrane for obvious reasons. But again under this would be an inch of building sand compressed down to avoid any piercing of the dpm from the hardcore u have put in. Its a hard one to explain as other builders will have different interpretations and techniques. Lots of vids on YouTube giving good advice. With regards to the foundations depth etc, the gentleman above gave good advice.
Answered10 December 2018
1
Anonymous user
Soil type is important, the excavation will need to be deep enough to locate the compacted clay and then further to be at least as deep as the existing foundations. There should be at least 200mm of compacted type1 hard core. If your home is in a radon zone then a radon barrier membrane is laid followed by 150mm - 200mm of flooring insulation. Above this is the DPC membrane followed by the concrete which for a nice flooring finish should be a high strength wet mix that is floated to a fine sheen. DPC then folded over edge block work and into cavity to form a complete radon / DPC seal. This work will require building regulations certification so every stage should be approved by the local inspector.
