An AGA is made primarily of cast-iron so can weigh a considerable amount.
If the floor in your kitchen is a solid construction then that's usually fine to carry the cooker.
If it's a different construction then you can still have an AGA, it's just that a support will probably be needed to ensure the floor is capable of carrying the cooker.
We can advise on what's best to do once we've carried out a home survey, however there are some guidance notes below.
First of all we'd best explain which is which!
By 'Floor Support' we're referring to a construction that goes under the floor to add strength and enable it to carry the weight of the AGA.
You wouldn't normally see the floor support - it's below the foor finish.
The plinth is the bit above the floor that you do see - not all AGAs need one; the S-Series, Freestanding Module, AGA 60, Dual Control and Total Control all have a plinth as part of the cooker.
Traditional heat storage models (designed before standard worktop heights) usually do, to raise the AGA (which is a non-standard height of 851mm) to the correct height - normally so the radius edge on the cooker's top plate is 5-10mm above the adjacent worktops, so usually a finished height of 910-925mm.
If the floor under the cooker is a solid concrete, screed, stone flag or similar construction it should be fine to carry the cooker's weight.
Constructed of floorboards nailed to timber joists.
Some may be capable of carrying an AGA however we'd always recommend a support is installed to be certain there won't be any movement when the AGA is fitted.
Usually there's a gap of 250mm-750mm between the bottom of the joists to the floor beneath (which is normally either dirt, or 'oversite' concrete in more modern builds). In this case an extra 'Sleeper Wall' in the area beneath the cooker is recommended.
It's usually easiest to build an extra 'sleeper wall' to support the joists in the area where the AGA will be fitted (don't forget to put a damp proof course 'DPC' to stop moisture rising up and rotting the wood joists).
If the joists run parallel to the wall behind the AGA (side to side as you stand looking at the cooker) then for a two or three oven AGA one support central to the cooker should be fine. For a four or five oven AGA, or one with an Integrated Module then it's best to put two supports in, spaced approximately one third of the distance in from each edge.
If the joists run perpendicular to the wall behind the AGA (front to back as you stand looking at the cooker) then an extra sleeper wall about 600mm out from the wall at the back, running the width of the cooker is best.
If the area beneath the AGA is deeper rather than building a wall it's easier to use builder's acrow props instead.
Quite often used in modern buildings.
Usually constructed of a solid concrete sub-floor with a layer (50-75mm) of insulation (which sometimes incorporates underfloor heating pipes) with an interlocking chipboard / fibreboard floor which 'floats' on the insulation. The floor finish (laminate, linoleum, or engineered boards) is then laid over the top.
These generally aren't suitable to carry the weight of an AGA - it's recommended to cut out the area beneath the cooker and make it solid using either a poured/cast concrete pad, or a combination of pre-cast concrete flags of the correct size to bring the solid part up to the height of the finished floor.
Tiles first, then the AGA
Normally we'd recommend the floor covering is laid before the AGA is installed.
For AGA 7 Series models AGA eR3 Series, AGA R3 Series, Total Control , Dual Control and AGA 60s the floor covering should extend the whole area beneath the cooker. (They have a slide-out tray for some of the electronics that could be obstructed if the cooker is installed and floor tiled up to it afterwards.)
For 'Traditional' AGAs it's still best to install the floor finish first and is best laid under the whole area of the cooker however it is acceptable for it to extend about 100mm under the 'footprint' of the cooker when you need to save some floor tiles or are using an expensive finish.
Asphalt Layer / Coating
Very rarely seen nowadays, it used to be laid as an insulating / damp reducing / levelling coating on old dirt floors (and sometimes over concrete or stone-flagged floors). Generally 25-40mm thick it's often black or red in appearance.
Since asphalt can be relatively soft we'd also recommend that the area beneath any AGA is removed and screeded/concreted so the cooker doesn't 'sink in' over time.
Asphalt floors are not at all suitable for oil fired AGAs - if there is any form of spillage or leak of oil on to the asphalt it will (chemically) 'melt' and damage it. The asphalt needs to be cut away in the area beneath the cooker and screeded or concreted back to the original height.
New Generation and S-Series AGAs
The AGA 7 Series, er3 Series, R3 series, Total Control, AGA Dual Control, S-Series and AGA 60 are fine to sit on a wood floor - the lower section incorporates a void which means no special precautions are necessary to allow for potential heat build-up (there won't be any).
Traditional Heat Storage AGAs
A traditional AGA needs to be set on a floor that is "non-combustible for a minimum thickness of 12mm".
Since traditional AGAs are usually set on a plinth to raise them to match (or be slightly above) the worktop level 'non-combustible' applies to the plinth (which the AGA sits on) - both our metal or concrete plinths meet this requirement, so it's fine for the AGA to be on a wood floor, providing it's on a plinth.