FFL stands for Finished Floor Level: the top of the completed floor measured to the drawing’s datum – in Australia, floor finishes included.
What FFL means
FFL is Finished Floor Level: the height of the top of the floor once the building is finished. In Australian practice that is the top of the finished walking surface – if the room is tiled, FFL is the top of the tile; if it is carpeted, the top of the carpet. Where the slab is left as a ground and sealed concrete finish, FFL and the top of the slab are the same number, which is exactly why the two get muddled on jobs that have both.
That reading is not universal, and it is worth knowing where the disagreement sits. A strand of UK usage takes FFL as the top of the screed or deck and excludes soft finishes such as carpet, on the reasoning that occupiers change them and their thickness varies. If you are working on a UK set, or with a UK consultant, confirm which reading the set uses before you set anything out from an FFL.
FFL is a level, not a thickness and not a height above the ground. It is one number measured to whatever datum the drawing set is working to, which is why the same FFL value should appear on the site plan, the floor plans, the sections and the details. Door thresholds, stair riser counts, window head heights, waterproofing upturns and ramp grades all get set out from it.
How FFL appears on a drawing
On Australian sheets, levels are written in metres to three decimal places and rounded to the nearest 5 mm, which is the convention AS 1100.301 sets for architectural drawing. UK sheets also give levels in metres to three decimal places, but that is British drawing convention and office practice – AS 1100 has no standing there. FFL turns up as a spot level in a box or against a level symbol on plan, and as a labelled line on section and elevation:
FFL RL 24.350
Read that as: the finished floor sits at reduced level 24.350 m above the datum. If the survey is tied to the Australian Height Datum, that is 24.350 m AHD. On a multi-storey job you will also see levels run from an assumed ground floor of 0.000 or 100.000, in which case an upper floor reads something like:
FFL +3.300 (SSL +3.240, 60 FLOOR BUILD-UP)
Wet areas are the usual exception to a single floor level per storey. The floor has to fall to a waste, so there is no one FFL across the room: the level is nominated at a stated point, normally the doorway or the high point of the fall, and the floor grades down from there. The structural drawings then carry a matching set-down so the screed to falls and the tiling still finish flush at the door:
FFL 24.350 AT DOOR, FALL TO WASTE. REFER STRUCT. FOR SLAB SET DOWN.
Terms it gets confused with
- SSL or SFL – structural slab level or structural floor level: the structural floor before screed and finishes. Lower than FFL unless the slab is the finish. With the 60 mm build-up above,
FFL RL 24.350pairs withSSL RL 24.290. - FCL – finished ceiling level, measured to the same datum.
- FGL – finished ground level, outside the building. Watch this one: the NCC’s minimum height above external finished surfaces applies to the slab-on-ground, not to the finished floor level, so checking FFL against FGL overstates your clearance by the whole floor build-up.
- AFFL – “above finished floor level”, a dimension origin rather than a level.
1200 AFFLon an electrical plan means 1200 mm up from the finished floor, wherever that floor ends up. - FL – plain “floor level”, which is ambiguous. On some sets it means finished, on others structural. Check the abbreviation legend before you set anything out. If the legend is thin, my A-Z list of engineering drawing abbreviations covers the rest of the level family.
AU and UK versus US
Australian and UK drawings work in levels to a datum: one vertical reference – AHD in Australia, Ordnance Datum in the UK, or an assumed site datum such as 100.000 tied to a nominated benchmark – with every level given in metres against it. US drawings do the same thing but call it elevation, usually in feet and inches, and the ground floor is very often set at an assumed EL 100'-0". The abbreviation shifts with the convention: FFE (finished floor elevation) or FF is more common than FFL on a US set, and the structural equivalent is written T/SLAB, T.O.S. or TOC rather than SSL. FFL is still understood in the US, but follow the sheet you are detailing to.
Where to check on your own set
- Title block and general notes – the datum statement and the benchmark it is tied to. If a set has no datum note, the levels are assumed and cannot be mixed with survey levels.
- Surveyor’s site plan – the benchmark RL and the existing levels around the building footprint.
- Architectural sections – the FFL to SSL relationship, and the floor build-up called up.
- Finishes schedule – the thickness that accounts for the difference.
- Structural drawings – these normally give SSL, not FFL. If a structural plan appears to give FFL, raise it as a query rather than assuming which one is meant.
One habit worth keeping: never scale a level off a drawing. If the FFL you need is not written down, it is a question for the designer, not an arithmetic exercise.
References
- Designing Buildings Wiki – Finished floor level (uses the narrower UK definition that excludes applied finishes)
- Levels on drawings (AS 1100.301 conventions summary)
- Geoscience Australia – Australian Height Datum
Other meanings of FFL
Outside drafting, FFL most often means Federal Firearms License (a US firearms dealer licence), and in casual sport talk a fantasy football league. Neither is related to drawings, but both dominate general search results for the bare letters.