There are three floors in Abhorsen's house proper, not including the tower which makes six.
In the cellar, there is a block of ice used to summon a flood from the Clayr's Glacier.
Ground Floor Edit
On the ground floor, there is a large garden outside, containing the well leading down to Astarael, and a Paperwing platform. Inside, there is the hall, the lower parlour (which is at the base of the tower), a store, a buttery, a kitchen, and stairs leading up and down.
Second floorEditOn the second floor, there are six small bedrooms, an armoury, and a workshop. There is also the upper parlour with stairs to the next level.
This is the highest proper floor, above is just the tower. There is the Abhorsen's bedroom, a music room, and stairs to the tower and roof gardens.
Here there is just the study, and outside are the roof gardens. A ladder leads to the top floor.
This is the top of the tower. The observatory is here, which has clear walls (not made of glass) allowing good vision.
Updates from the book 'Clariel' tell us there is also a secret room below the waterfall where Abhorsens kept free magic creatures prisoner for torture and interrogation. Also home to free magic creatures imprisoned and yet to be destroyed. It is likely that many floors below this area is where Kerrigor, in the form of a black cat, sleeps.
There are only four ways to enter or leave Abhorsen's house. These are via the door in the Long Cliffs, via Astarael's well, by boat, or by paperwing.
To enter via the Long Cliffs you must walk up hundreds of switch-backing wide, low steps, carved with intricate patterns, which ends at the cliff face. There, Mosrael must be used to reveal the door, although it will only appear when the sound from the bell has faded. This door is guarded by a sending presumably created by a former Abhorsen, although it will only try to prevent things from passing it; if they manage this, it will not pursue them. From inside this door, Charter marks light the way along an upwards sloping tunnel, including marks for fleetness. At the end of this tunnel is another door, also guarded by a sending, and on the side of Abhorsen's house is a sending in the shape of a delicate silver portcullis and iron padlock. Here, the path reaches the River Ratterlin, steps leading down to a series of stepping stones across to the island Abhorsen's House is on; this is Abhorsen's Bridge. It is likely that a more solid bridge would reduce the effect that being on an island has in terms of defending against the Dead.