Bohol Heritage & Architecture: Coral Stone, Bahay na Bato, and the 2013 Reconstruction

The quarry is offshore. Almost every substantial pre-twentieth-century building in Bohol — church, watchtower, the ground floor of an old town house — is cut from the reef limestone the island is made of, and follows what that stone will and will not do.

Cutting the reef

Coral limestone is a bioclastic rock — compacted reef material rather than a dense igneous stone — which is why it could be quarried with hand tools. Blocks came off the reef flat at low tide, when the face is exposed and the stone is still wet and soft. It hardens as it dries. The sequence is the technique: cut wet, cure dry.

Curing did more than harden the block. Fresh reef stone carries sea salt, and salt left in a wall migrates outward as it dries, crystallises under the surface, and pushes the face off in flakes. Blocks were stacked in the sun to sweat it out first.

The mortar came from the same material, burnt rather than cut. Coral heated in a kiln leaves quicklime; slaked with water and mixed with sand it becomes lime mortar, which then reabsorbs carbon dioxide from the air and turns back into limestone. Block and binder are chemically the same rock, so the wall behaves as one mass rather than as stone plus adhesive.

The egg white in the finish coat sounds like folklore until it is checked. Analysis of the mortar has found proteinaceous amine traces consistent with albumin, the protein in egg white. Albumin is hydrophobic — it repels water — and coral limestone is porous. In a climate that delivers monsoon rain sideways for months, that coat is the wall’s raincoat.

The labour came from polo y servicio, the colonial draft obliging adult male subjects to a set number of days of unpaid public works each year. The church at Baclayon, completed in 1727, was raised under it with an estimated 200 indigenous workers on site; the Jesuit mission there dates to 1596, the Recollects took over in 1768, and a bas-relief of Saint Andrew on the tower carries that phase’s date, 20 May 1777. Walls of this mass are only affordable in a parish with no cash economy because the labour was not paid for.

Coral block is strong in compression and close to worthless in tension, so a wall built from it is a stack that stands by weight. Every opening is a hole in the load path. Windows are small, high and widely spaced, and the wall between them is thick — well over a metre at Baclayon. The nave, the long central hall where the congregation sits, is a masonry box with a timber roof dropped on top, helped where necessary by a buttress: masonry built against the outside face to add weight where the wall would otherwise hinge outward. Beside most of these churches stands the convento, the priest’s residence and parish office; at Baclayon it holds the parish museum.

Lime mortar, Portland cement, and how to read a repair

This explains more damage than the earthquake did. In a lime-mortared wall the joints are deliberately the softest part of the assembly. Moisture that gets in travels to the joint and evaporates there, so if anything decays it is the mortar, which can be raked out and replaced without touching the stone. Portland cement is stronger than coral limestone and far less permeable. Repoint a coral wall with it — pointing is the mortar worked into the outer face of a joint — and that escape route closes. Water still enters, as it always does in a wet climate, and now leaves through the block face instead. Salts crystallise behind the face and the stone spalls: the surface flakes off in sheets, exposing fresh material to do it again. A cement repair does not fail. The original stone beside it fails.

That looks like hard grey joints standing proud of soft mottled block, the block hollowing at the joint edges while the mortar stays sharp. Two further tests separate original fabric from repair. Ashlar — squared block laid in regular courses of even height — gives way at a rebuild to a change in course height, or to coursed rubble, roughly shaped stone in rough bands. And masons bond a wall by overlapping blocks, so a straight vertical seam running a wall’s full height means two pieces of work meeting each other.

15 October 2013: why the towers went and the naves mostly stayed

These are unreinforced masonry buildings — no steel anywhere in the wall. Under gravity that is fine, because gravity only pushes down. A seismic wave is lateral: it shoves the building sideways and pulls it back, and on the return stroke one face of every wall goes into tension. Lime mortar has almost no tensile bond, so a coral wall does not crack the way concrete cracks. It opens at the joints and comes apart into the blocks it was assembled from.

Height and slenderness set the order of failure. A bell tower is tall, narrow at the base, heavy with bronze at the top, and often only weakly bonded into the nave wall beside it; lateral force grows with height and concentrates at that small base. Where bells hang instead in an espadaña — a pierced gable wall above the façade rather than a freestanding tower — the mass sits lower and ties into the wall below. The third weak point is the wall-to-roof connection: a heavy timber roof sits on the wall head by gravity rather than by fixing, so the two move independently and the wall loses the restraint at its top.

The magnitude 7.2 earthquake, epicentre in central Bohol, followed all three rules. Loon’s church, the largest in the province, collapsed. Maribojoc collapsed. Loboc lost its façade and much of its nave. At Baclayon the portico and bell tower came down while the thick perimeter walls held. Dauis was damaged and repaired between 2015 and 2017. Twenty-one churches in the Diocese of Tagbilaran were damaged and have since been repaired.

What a reconstruction actually is

Restoration involved the National Museum of the Philippines, the National Historical Commission and the National Commission for Culture and the Arts, plus artisans retrained in coral-stone working and lime-mortar preparation — knowledge that had partly lapsed. Where collapsed blocks could be catalogued as they were lifted, they went back into the wall. Baclayon reopened in February 2018. Loboc’s began in December 2017, recovering the side and main retablos — the carved altar screens behind and beside the altar — and the ceiling paintings from the rubble, and reopened in 2020.

Which raises the question a listing page cannot ask. If a nave is rebuilt from its own catalogued blocks, in new mortar, by masons trained for the job, what is it? Three positions are defensible and do not reconcile. One holds that the fabric is the artefact, so reset blocks make a high-quality replica. The second holds that a church is a plan, a volume and a congregation, and the blocks only the medium. The third sidesteps both: repair should be readable, new work distinguishable from old.

No Bohol church is one thing: most south-coast walls are part eighteenth-century, part twentieth-century repair, part post-2013 reconstruction.

The corridor, the plaza, and the towers on the same line

Baclayon sits minutes east of central Tagbilaran, and the chain continues through Loay, Dimiao, Valencia, Jagna and Guindulman; west and north it runs to Loon and Maribojoc, and Dauis is a short crossing onto Panglao.

Each was the seat of a parish that was also an administrative unit, and the colonial town plan was a template repeated down the coast: a plaza, the church on one side, the convento beside it, the tribunal or municipal building across the open ground, the market and principal houses filling the rest. It organised the settlement — where you lived, how far you walked to Mass, who could see you doing it. Most towns still have the plaza and the church on it.

Siting followed water and approach as much as doctrine. Loboc stands back from the coast on the river, on the navigable route inland. Dauis, begun in 1863 and finished in 1923, has a well at the foot of its altar: the church was built over its own water source, a siting decision before it is a story, and the local account of townspeople sheltering there during raids is tradition rather than record.

Paired with the coastal churches was a network of stone watchtowers built against Moro raiding fleets: the tower saw the sail, the bell moved the town. The Punta Cruz watchtower, at the western tip of Maribojoc, is the one worth the drive. Completed in 1796, it is an isosceles triangle in plan with the apex pointed seaward — the only documented triangular watchtower in the country. Two long walls, each facing a different coastal approach, give one small garrison a sightline along both. The Panglao watchtower is hexagonal, five storeys, and dated 1851 by the year carved into its lowest chamber. It predates the church beside it and became the belfry later — adaptive reuse, putting an existing building to a new purpose, a century before the term existed.

The interior sequence repeats too: an open bright plaza, a compressed low portico, then the nave opening above and ahead — dim, markedly cooler, lit from small high windows, the eye pulled to a lit altar. Compression, release, direction. Never a stylistic preference; the point of the plan.

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Bahay na bato, and the timber frame underneath it

Beneath the colonial system sits an older one that never went away. Philippine timber building is post construction: hardwood posts, harigue, carry the whole frame from ground to ridge, and the walls are infill panels holding nothing up. The frame flexes, deflecting and returning under wind or a seismic shove, where a stack of coral block has no give at all — which is why the bahay na bato puts one on top of the other.

House of stone, though only the lower half is. The masonry or coral-block ground floor defeats termites, survives flooding, and puts weight and lateral stiffness at the bottom; it is storage and passage, not living space.

The upper floor is light timber, and that is where the household lives. Being framed rather than stacked, it opens on every side, and the openings work in pairs: large sliding windows at standing height, and ventanillas beneath them — low shuttered openings behind a turned-wood grille that move air across the floor, where people actually sat, ate and slept, so the room ventilates at two heights at once. The panels are capiz, thin translucent windowpane oyster shell set in sliding grilles, admitting a soft even light while blocking direct sun and the heat with it — the opposite of glass, which was imported, costly, and would have cooked the room. Overhanging it all is the volada, a cantilevered gallery outside the living rooms, and beyond that a deep eave, which is what lets the windows stay open in rain.

Tagbilaran’s Poblacion I holds the surviving examples, most privately owned and best read from the street. Beldia House (Villa Mercedes), built in 1858, sets a floating volada over massive coral-stone ground-floor walls under a curving gambrel roof of clay tiles the sources call unique in the province; its jalousie windows upstairs — louvred glass slats — replaced the original wooden panels, a legible alteration worth noticing. Casa Rocha, in Sitio Ubos, is dated 1831 by an inscription in its own kitchen wing and pairs a coral-stone ground floor with a timber upper storey built without the usual volada.

Nobody builds this type any more, and the reason is air conditioning. Once a room can be cooled mechanically every element becomes optional, and each goes for its own small reason: capiz swapped for glass, ventanillas boarded because they leak conditioned air, the volada glazed in for floor area. The system only works whole, which is why several surviving heritage houses are hotter today than they were designed to be.

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The twentieth-century layer: concrete and bronze

After 1898 the structural vocabulary changes completely. Reinforced concrete arrives, and with it a frame that resists tension as well as compression — so openings can be wide, walls thin, and a building need no longer be a stack. What follows is neoclassical civic architecture: symmetrical block, pedimented centre, colonnade, axial approach. The siting is the political part. The new government buildings went onto the plazas the church complex had already organised, facing or flanking the church rather than replacing it. The town did not move; its centre of gravity did. The old Provincial Capitol in Tagbilaran is the clearest local example.

The blood compact between Miguel López de Legazpi and Datu Sikatuna, chieftain of Bohol, was sworn on 16 March 1565, each cutting an arm and mixing blood into a shared cup of wine. The monument at Barangay Bool, east of central Tagbilaran, is a 1965 bronze group of five life-sized figures around the toast, by Napoleon Abueva — born in Tagbilaran in 1930, declared National Artist in 1976. That makes the sculpture a heritage object in its own right, independent of what it commemorates.

The location is a separate question. In 2005 the National Historical Institute identified Barangay Hinawanan in Loay as the documented site, citing Legazpi’s records describing a deep well between two rivers near the anchorage; the well is still there, and the Sandugo blood compact site marks it. Bool still receives most of the visitors. Both facts hold at once.

What these buildings do on a Tuesday afternoon

Almost everything here is still in use, which changes how it should be visited. The churches are working parishes whose Mass and fiesta schedule outranks visitors; the Tagbilaran heritage houses are private homes.

A Tuesday afternoon at Baclayon is a few people in the back pews, someone sweeping the aisle, a small queue at the convento museum, tricycles idling in the shade outside. The building is doing what it was built to do, three centuries on, with a meaningful share of its fabric younger than a decade. That is the practical answer to the restoration argument: a church rebuilt and used is a different object from a ruin stabilised and interpreted, and Bohol has chosen the first.

The churches and religious sites directory and the heritage and historical landmarks directory list the buildings one by one. For a driving day, the heritage churches route covers the corridor east from Tagbilaran.