Historic masonry block of flats

1. General Information

Report #: 206

Report Date: 2010

Country: Italy

Housing Type: masonry

Housing Sub-Type: unreinforced

Author(s): Mario Rodriguez, Francisco G. Jarque

Last Updated: 2012

Regions Where Found: This housing type is in Abruzzo Region, Province of L Aquila, and is very frequent in small medieval villages built in mountainous areas. 90% of the Province of L Aquila is mountainous and about 50% of its municipalities have less than 1.000 inhabitants. Urban structures and buildings built since the Middle Age are very common

Summary: This housing type is typically built on sloped terrain (pic.1). Buildings share common walls with adiacent buildings and the average number of floors ranges from 3 to 5 (pic. 2). The ground floor is sometimes used as cellar or warehouse, whereas the upper floors are used for residential purposes. The walls are built using lime mortar to connect elements that are either bricks or rubble stones or a mix of both in which the bricks are positioned in thin layers every 1.5 - 2 m, in order to align and stabilize the stones. The last floor (attic) is sometimes more recent (probably from the beginning of the XX cent.) and built with different materials (i.e. tuff) or specific construction techniques (i.e. “muro a cassetta”, whose bricks are positioned in order to made a very light structure). The floor structures are vaults of different shapes, materials and resistance depending on the function. At the lower levels they are usually thick and made of stones connected by lime mortar, whereas at the upper floors they are made by bricks. At the last level the vaults are usually made by one single brick layer and their sides are usually kept half empty with no walkable floor. The roof is made of timber and it is double pitched, sloping down towards the front and rear walls. This building type has shown a good seismic performance, because the adiacent blocks work all together to stand the earthquake. Strenghtening interventions have been carried out after the main earthquakes.

Length of time practiced: More than 200 years

Still Practiced: No

In practice as of: nan

Building Occupancy: Residential, 5-9 units

Typical number of stories: 3-4

Terrain-Flat: Never

Terrain-Sloped: Typically

Comments: The building type dates back to the middle ages with a complex later evolution over time expecially since the 18th century.

2. Features

Plan Shape: Rectangular, with an opening in plan

Additional comments on plan shape: The plan and the overall shape of the buildings are influenced by the orography. People tried to build as much regurarly as possible, but the result were rectangules with not right angles and sides with very different measures. Sometimes walls are curved.

Typical plan length(meters): 3 - 4

Typical plan width (meters): 3 - 4

Typical story height (meters): 2.5 - 3.5

Type of Structural System: Masonry: Stone Masonry Walls: Rubble stone (field stone) in mud/lime mortar or without mortar (usually with timber roof)Masonry: Unreinforced Masonry Walls: Brick masonry in mud/lime mortarMasonry: Unreinforced Masonry Walls: Brick masonry in mud mortar with vertical postsMasonry: Confined Masonry: Clay brick/tile masonry with wooden posts and beamsWooden Structure: Load-bearing timber frame: Masonry with horizontal beams/planks at intermediate levels

Additional comments on structural system: In the same structure there are usually different construction systems. It depended mainly on the availability of building materials, on the position of the single construction system as part of the overall structure and on the history of the buildings, to whom new rooms were added as families grew.

Gravity load-bearing & lateral load-resisting systems: Gravity load-bearing system: thickness and materials depend on the floor level. Walls are thicker at the ground floor and thinner at the upper levels. They are usually made by a mix of bricks and rubble stones in which the bricks are positioned in thin layers every 1.5 - 2 m, in order to align and stabilize the stones. People used to reinforce perimetral corners placing shaped stones usually up to the 2nd floor. At the upper level there are often tuff walls or characteristic structures such as those called “muri a cassetta”. They are made by two-wythe walls, in which every two courses of bricks laid edge on there is one course laid face-up, to connect the vertical bricks. The space between the vertical layers is empty, so that the thermal performance of the structure benefits from it and the wall is light. Vaults at the upper floors are often supported by timber frames filled by a partition made by a one-wythe wall, whose bricks are laid edge on. The load bearing structure and the partition are covered by plaster and the wall thickness is about 10 cm. The lime mortar joints are 3-5 mm thick.

Typical wall densities in direction 1: 10-15%

Typical wall densities in direction 2: 10-15%

Additional comments on typical wall densities: nan

Wall Openings: Every room has usually one window on the external walls. They aligned the windows upright on the facades, but the needs of residents and owners changed over time so that the existing opening layout have been often modified. Misalignments are very common. The openings account for approximately 10% -15% of the wall surface area.

Is it typical for buildings of this type to have common walls with adjacent buildings?: Yes

Modifications of buildings: Door and window openings have often been modified. Very frequent modifications are misalignments, enlargements, windows changed in balcony doors and windows bricked up and opened in different positions. The layout of apartments is quite irregular due to changes occurred over time. As families expanded, they built new storeys or just part of them or they bought rooms from the neighbours. This is the reason why inside the single flats there are often short flights of stairs and the plans are usually irregular, sometimes almost “labyrinthine”.

Type of Foundation: Shallow Foundation: Rubble stone, fieldstone strip footing

Additional comments on foundation: nan

Type of Floor System: Vaulted masonry floor

Additional comments on floor system: The traditional floor system is the vaulted masonry floor. We currently also find the shallow-arched masonry floor and the metal beams light flooring. The first one was introduced at the beginning of the XX cent and in particular after the earthquake occurred in 1915. The second one was introduced after the earthquake occurred in 1984.

Type of Roof System: Wooden structure with light roof covering

Additional comments on roof system: The traditional roof system is the wooden structure with light covering. We currently also find the cast-in-place metal beam-supported hollow flat tiles and concrete roof, which was introduced after the 1984 earthquake

Additional comments section 2: nan

3. Buildings Process

Structural Element Building Material (s) Comment (s)
Wall/Frame Mix of bricks and rubble stones

average shear strength: 6.2 - 9.0 N/cmq (Baila, A., Binda, L., Borri, A. et al. (2011) - Manuale delle murature storiche, Analisi e valutazione del comportamento strutturale Vol.1, p. 292)|

Foundations Mix of bricks and rubble stones or rocknan
Floors Brick vaultsnan
Roof Wooden beamsnan
Other nannan

Design Process

Who is involved with the design process?: None of the above

Roles of those involved in the design process:: The construction process was carried out by masons, so engineers and architect were usually not involved.

Expertise of those involved in the design:: nan

Construction Process

Who typically builds this construction type? Mason

Roles of those involved in the building process: The construction was based on the mason's experience. Tricky works such as the construction of vaults were committed to specialized teams of masons.

Expertise of those involved in building process: Masons were supposed to meet the owner's needs, working on a budget and using the construction materials available in the area. Their main ability consisted in finding the right balance among forces acting in different directions on light and thin structures. They basically had to make sure that the stiffness of all the structural elements was coherent as a whole so that, in the event of an earthquake, the building would perform a box-behaviour.

Construction process and phasing: The construction process was influenced by the owner's budget, the availability of materials, the characteristics of the area (orography) and of the surrounding buildings. The works usually took place in one phase. Sometimes at a later time, storeys or just single rooms were added in order to meet the owner's needs. The construction tools were simple.

Construction issues: nan

Building Codes and Standards

Is this construction type address by codes/standards? Yes

Applicable codes or standards: With Royal Decree-Law n.573, on 29 April 1915 the area was included among the seismic ones, due to the earthquake occurred on 13 January 2015. This Royal Decree-Law ruled both new construction and reparation works on damaged buildings (Title II Reconstructions, Title III Reparations)

Relevant following regulations: - Royal Decree-Law n.2089, 23 October 1924 Law n. 64, 2 February 1974, Provvedimenti per le costruzioni con particolari prescrizioni per le zone sismiche (Measure for constructions with specific rules for seismic areas) - Ministerial Decree 16 January 1996, Norme tecniche per le costruzioni in zone sismiche (Technical standards for constructions in seismic areas) - Ministerial Decree 14 January 2008, D.M. 2008 Norme Tecniche per le Costruzioni (Technical standards for constructions), which includes how to repair existing buildings made by bricks and stones.

The standard currently in force is: Decree 17 January 2018, Aggiornamento delle “Norme tecniche per le costruzioni” (Update of the Technical standards for constructions).

Technical suggestions and best practices are included in “Linee guida per riparazione e rafforzamento di elementi strutturali, tamponature e partizioni” written by ReLUIS consortium

Process for building code enforcement: nan

Building Permits and Development Control Rules

Are building permits required? Yes

Is this typically informal construction? Yes

Is this construction typically authorized as per development control rules? No

Additional comments on building permits and development control rules All these buildings are currently subjected to national and local codes that are much more recent than the constructions themselves

Building Maintenance and Condition

Typical problems associated with this type of construction: These buildings need structural strengthening due to their age, their structural fragility, the poverty of their materials and even because throughout the centuries they have been subjected to several hearthquake tremors, which made them every time weaker (incremental damage)

Who typically maintains buildings of this type? Owner(s)

Additional comments on maintenance and building condition nan

Construction Economics

Unit construction cost: This construction typology is no longer built and is usually replaced by other typologies made of reinforced concrete frames, whose cost ranges from 1.500 to 2.500 euros/sq m

Labor requirements: nan

Additional comments section 3: nan

4. Socio-Economic Issues

Patterns of occupancy: One family per house

Number of inhabitants in a typical building of this construction type during the day: <5

Number of inhabitants in a typical building of this construction type during the evening/night: <5

Additional comments on number of inhabitants: Family units are usually small (⇐4 people). They are often retired people

Economic level of inhabitants: Low-income class (poor)Middle-income class

Additional comments on economic level of inhabitants: Retired people who live in these houses have often a low income. Families usually belong to the low or middle income class. Lots of houses are used as holiday homes by people from the area who live and work in other parts of the country. In villages with beautiful views sometimes apartments are bought by foreigners from high-income class, who spend there their holidays or few months out of the year

Typical Source of Financing: Owner financedPersonal savingsInformal network: friends or relativesSmall lending institutions/microfinance institutionsOther

Additional comments on financing: State aid for the reparation and strengthening of the buildings after earthquakes

Type of Ownership: RentOwn outright

Additional comments on ownership: nan

Is earthquake insurance for this construction type typically available? No

What does earthquake insurance typically cover/cost: nan

Are premium discounts or higher coverages available for seismically strengthened buildings or new buildings built to incorporate seismically resistant features? No

Additional comments on premium discounts: nan

Additional comments section 4: nan

5. Earthquakes

Year Earthquake Epicenter Richter Magnitude Maximum Intensity
1706Campo di Giove (L'Aquila)6.6MI
1762Poggio Picenze (L'Aquila)5.9MI
1904Rosciolo (Marsica)5.6MI
1915Paterno (Marsica)7MI
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