There are three building categories for the Island Sanctuary. They are "Cabin & Fields", "Processing Facilities", and "Landmarks".

Cabin & Fields

Cabins

The hideaway can have one Cabin, unlocked at Sanctuary Rank 1. The Cabin allows players to sell gathered items for those Islander's Cowries () and Seafarer's Cowries (), as well as spending those currencies for attire, hairstyles, minions, mounts, etc.

Upgraded Cabins unlock upgrades for the Pasture and Cropland.

Building	Unlock Rank	Build Time	Island EXP	Materials
Cozy Cabin I	1	None	750	10 Island Palm Log 10 Island Palm Leaf 5 Island Vine 5 Island Stone 5 Island Sand
Cozy Cabin II	4	None	1,755	10 Island Log 10 Island Vine 10 Island Limestone 5 Island Palm Leaf 5 Island Copper Ore
Cozy Cabin III	7	None	2,565	10 Island Log 10 Island Limestone 10 Island Cotton Boll 5 Island Hemp 5 Island Clay

Cropland

The hideaway can have one Cropland, unlocked at Rank 2. The Cropland allows players to grow Produce from Produce Starters (seeds or sets).

Upgraded Croplands provide additional plots for produce, and allows automation at upgrade III.

Building	Unlock Rank	Build Time	Materials
Cropland I	2	None	Free
Cropland II	4	2 hours	1,000 Seafarer's Cowries
Cropland III	7	4 hours	1,500 Seafarer's Cowries

Pastures

The hideaway can have one Pasture, unlocked at Rank 2. The Pasture allows players to gather Leavings from animals.

Upgraded Pastures hold additional animals, and allows automation at upgrade III.

Building	Unlock Rank	Build Time	Materials
Pasture I	2	None	Free
Pasture II	4	2 hours	1,000 Seafarer's Cowries
Pasture III	7	4 hours	1,500 Seafarer's Cowries

Processing Facilities

Workshops

The hideaway can have a maximum of 3 Workshops. Two are available when Workshops unlock at Rank 3, and the third becomes available at Rank 5.

Each workshop allows mammets to create handicrafts, which are exported for Seafarer's Cowries () when completed.

Upgraded Workshops increase the value of their handicrafts.

Building	Unlock Rank	Build Time	Island EXP	Materials
Workshop I	3	None (first) 1-2 hours (others)	1,425	10 Island Log 10 Island Palm Leaf 10 Island Limestone 5 Island Vine 5 Island Sand
Workshop II	6	6-7 hours	2,300	15 Island Log 15 Island Limestone 10 Island Hemp 5 Island Clay 5 Island Copper Ore
Workshop III	8	11-12 hours	2,760	15 Island Iron Ore 15 Island Leucogranite 10 Island Log 10 Island Hemp 3 Raw Island Garnet

Granaries

The hideaway can have a maximum of 2 Granaries, both of which are available when Granaries unlock at Rank 5.

Each workshop allows mammets to go on expeditions to forage for various Normal materials, and a fixed amount of Rare materials which cannot otherwise be gathered on the island.

Upgraded Granaries yield more Rare materials from expeditions.

Building	Unlock Rank	Build Time	Island EXP	Materials
Granary I	5	1-2 hours	1,425	10 Island Palm Log 10 Island Log 10 Island Clay 10 Island Copper Ore 5 Island Vine
Granary II	6	6-7 hours	2,300	15 Island Palm Log 15 Island Log 10 Island Hemp 5 Island Clay 5 Island Tinsand
Granary III	8	11-12 hours	2,760	15 Island Log 15 Island Iron Ore 10 Island Leucogranite 10 Island Clay 3 Island Spruce Log

Landmarks

The hideaway can have a maximum of 4 Landmarks. The first become available at Rank 4, second at Rank 5, third at Rank 7, and fourth at Rank 9.

Note that the Water Otter Fountain is not required to fill all Landmark slots.

Each constructed landmark increases the maximum Workshop Groove (which increases the value of Workshop exports).

Building	Unlock Rank	Build Time	Island EXP	Materials
Quixotic Windmill	3	11-12 hours	??	15 Island Log 15 Island Limestone 10 Island Palm Log 5 Island Vine 5 Island Copper Ore
Towering Tree Fort	3	11-12 hours	??	15 Island Palm Log 15 Island Log 10 Island Limestone 5 Islewort 5 Island Vine
Boiling Bathhouse	5	11-12 hours	1,995	15 Island Log 15 Island Log 15 Island Limestone 10 Island Clay 10 Island Palm Leaf 3 Island Clam
Lominsan Lighthouse	9	11-12 hours	2,460	15 Island Leucogranite 10 Island Hemp 10 Island Log 10 Island Clay 3 Island Silver Ore
Water Otter Fountain	9†	11-12 hours	??	15 Island Leucogranite 15 Island Limestone 10 Island Clay 10 Islewort 3 Island Alyssum

† A Water Otter Fountain Permit is required for the construction of the Water Otter Fountain.

This permit can be obtained from the Horrendous Hoarder in The Cozy Cabin in exchange for the following items (from Level 90★★★ Expert Crafting, requires Master Recipes X books):

Items Required for Turn in	Crafted by	Materials to Craft 2x Items
2 Water Otter Fountain Hardware		2 Igneous Glioaether 4 Bismuth Ore 2 Phrygian Gold Ore
2 Water Otter Fountain Resin		2 Aqueous Glioaether 2 Dynamite Ash 2 Sideritis Leaves
2 Water Otter Fountain Lumber		2 Verdurous Glioaether 2 Red Pine Log 2 Snow Flax 2 Saiga Hide

Pathfinder Hideaway Expansions

The Pathfinder mammet expands the land available in the hideaway for constructing Processing Facilities and Landmarks.

Building	Unlock Rank	Build Time	Island EXP	Unlocks	Materials
Pathfinder Mk I	1	None	??	Facility I & II slots	Free
Pathfinder Mk II	4	None	??	Landmark I slot	500 Seafarer's Cowries
Pathfinder Mk III	5	None	??	Facility III & IV slots Landmark II slot	1,000 Seafarer's Cowries
Pathfinder Mk IV	7	None	??	Facility V slot Landmark III slot	1,500 Seafarer's Cowries
Pathfinder Mk V	9	None	3,280	Landmark IV slot	3,000 Seafarer's Cowries

References

u/Sewer-Rat's Island Sanctuary Comprehensive Guide: https://docs.google.com/spreadsheets/d/1R4UKA2zZ1MZ7sRUEBAi2Eh0NCVPbb1iQh8BjoQ_vVX4/htmlview?usp=sharing&pru=AAABgwSbH3g*x7be6s4PQoQeqKYiuF48tg#

Island Sanctuary

Animals • Crafting Log • Hideaway Structures • Isleworks Handicrafts
Materials • Produce • Stock Stores • Tools

Island Hideaway Structures

Cabin & Fields	The Cozy Cabin • Cropland • Pasture
Processing Facilities	Workshops • Granaries
Landmarks	Quixotic Windmill • Towering Tree Fort • Boiling Bathhouse • Lominsan Lighthouse • Gamboling Garden • Quaint Clock Tower • Sanctuary Sanctuary Special: Water Otter Fountain • Uncharted Course • Aetherial Arbor