Ramro Mato / राम्रो माटो Earthen Building. Rammed Earth · Kathmandu

Field Notes & Practice

Rammed Earth —What We Have Found

Questions our clients ask most, answered from years of building, testing, and learning on site across Nepal.

800+ Years — old RE structure, witness in Mustang.

13 N/mm² — peak compressive strength in our testing

6 Generations — lifespan of a well-built RE home in natural material

Standardisation Strength Moisture Lifespan Soil Mix Design Cost Thermal Seismic Fire Maintenance Finish Not Right For Starting Point

When people come to us asking about rammed earth, they arrive with two things: genuine curiosity and a quiet list of doubts. They have seen a wall somewhere — video of sustainable building project, at a resort, in a talk-show, on a vacation to Mustang — and something about it stayed with them. Then the practical questions follow.

This page is our attempt to answer those questions plainly, drawn from what we have actually built, tested, and observed. We work exclusively with stabilized rammed earth across Nepal, from Kathmandu valley residences to high-altitude cold storage in Mustang. What we share here reflects that practice — and we hold it lightly, because the material continues to teach us.

01 The Standardization Dilemma: "How do you build with earth? Is it comparable to standard practice, and how do you know the wall will perform?"

This is nearly always the first concern, and it is a fair one. Cement arrives with a grade. Steel comes with a mill certificate. Soil does not. The variability is real — and it is why we run a material testing programme specific to each project.

We collect soil samples from candidate sources within practical distance of the site. Each material goes through sieve analysis to map its particle size distribution. We run Proctor compaction tests to establish optimum moisture content and maximum dry density. We then design a blended mix — combining a clay-rich binder soil with sand, stone dust, and aggregate — calibrated against theoretical grading models. Trial specimens are cast, cured, and tested in compression to integrate with project structural calculation.

For the Bagaicha Adventure Resort in Nawalpur, all materials were sourced within 14 kilometres of the site. Ten mix trials were run — varying clay content, sand, stone dust, aggregate, and stabiliser combinations, including lime — before the final mix was confirmed through laboratory compression testing and material sourcing. For the Budhanilkantha villa, seven soil samples from seven separate locations were evaluated, each with a distinct earth tone. The binder clay was selected on the basis of performance, and the final blended mix reached a maximum dry density of 2.282 g/cc at an optimum moisture content of 11%.

What happens before construction begins

Soil samples collected from candidate sources near the site
Sieve analysis on each material to map particle size distribution
Proctor compaction test to establish optimum moisture content and maximum dry density
Mix design calibrated against Theoretical Grading Models for Rammed-Earth,
Trial specimens cast, cured, and compression-tested
Structural design based on site specific soil samples with lab-confirmed results

The goal is to turn an unspecified natural material into a documented, tested, and repeatable building element. It takes time at the front end. It gives confidence throughout the project.

02 Compressive Strength

How strong is rammed earth? Where does it sit against materials people already know?

Comparing strength figures helps ground the conversation. Our cement-stabilized rammed earth (CSRE) sits at the upper end of masonry materials — in the range of first-class brick and above, depending on mix design and compaction quality.

Material

Compressive Strength

Relative Strength

Adobe (mud brick)

0.75 – 3.0 N/mm²

Unstabilized rammed earth (NZS min.)

2.0 -6.0 N/mm² Second class brick

4 – 8 N/mm²

First class brick

up to 12 N/mm²

Our CSRE (Ramro Mato)

8 – 13 N/mm²

Standard RCC (M20)

20 N/mm²

The Nagarkot Residence specimen returned a peak of 13.169 N/mm² at a breaking load of 296.3 kN — a figure we are comfortable referencing in a structural design report, and one our structural engineers work from directly.

CSRE is not a replacement for horizontal tensile element such as ring beams, although they can be designed to integrate with floor diaphragm. What it replaces is the walling system — and as a walling material, it performs at or above the brick and mortar walls most homes in Nepal are built with today.

03 Moisture & Water Management

How does rammed earth handle moisture and rain?

Earth and water have a relationship that requires attention at the design stage. Rammed earth handles moisture well when the building is designed correctly — and poorly when it is not. There is no shortcut around this.

The traditional wisdom in earthen architecture captures it simply: a good boot and a good hat. The boot is a raised foundation with a properly installed damp-proof course, keeping the base of the wall clear of ground moisture. The hat is a generous roof overhang that prevents direct rain from running down the wall face. These are not decorative decisions — they are structural ones, and we treat them as such on every project.

Beyond protection from water, rammed earth has a quality that most modern wall systems lack: it breathes. Earth walls absorb and release moisture vapour, buffering the interior from the humidity swings of the exterior. Clients in our completed buildings consistently describe interiors that feel stable without any active humidity control. There is no condensation on surfaces, no mould, no fungal growth — provided the damp-proof course is correctly installed and junctions with floor and roof are properly sealed.

Finish options for moisture management

Penetrative sealants — while allowing vapour transmission; for exterior walls
Linseed oil — natural, breathable, deepens the earth tone slightly
Breathable wax — interior application; surface protection without sealing
Natural clay-based paint — interior use; maintains vapour permeability
No finish — viable for sheltered interior walls; the wall surface is the finish

04 Durability & Lifespan

How long does a rammed earth building actually last?

The answer begins not in a laboratory, but in Mustang.

The Kag Chode Thupten Samphel Ling monastery at Kagbeni was built in rammed earth around 600 years ago. The walls lean inward as they rise — a vernacular seismic detail — with horizontal timber beams laid at intervals throughout the wall mass, visible from the exterior. The holes left on the wall, where birds reside, may have been as they were thorough put-log to tie the formwork and for scaffolding. The Jong Fort in Mustang is estimated to be around 800 years old. It has no roof. It has had no formal maintenance. The walls are weathered, but they are standing tall — a testament to what rammed earth does when the two things that typically destroy buildings, water ingress and structural failure, are absent.

The Kings Palace at Lo Manthang is in comparatively good condition, with recent repairs carried out respecting both traditional techniques and contemporary engineering methods.

From our field observations — Mustang, Nepal

An 800-year-old fort wall, no roof, no maintenance, still standing. The question is not whether rammed earth lasts — it is whether the building around it is looked after.

For a client building a home in Kathmandu today — with engineered foundation, proper damp-proof course, designed roof detailing, and reinforced wall construction — a well observed lifespan is at minimum six generations, provided the building co-produce have similar specificity that usually ascribes to natural materials, such as stone, timber, lime; with cyclic maintenance.

The wall itself, given the right conditions, will outlast its modern counterparts.

What lifespan actually depends on

Foundation quality and damp-proof course — the boot (since RCC has been a staple material for this job, it realistically annexes the lifespan of the structure built on top of it)
Roof design and overhang — the hat
Mix design and compaction — the wall itself
Ongoing building maintenance — roof repairs, drainage management
The wall, given these conditions, is typically the last element to fail

05 Soil Selection

Can you use any dirt? What soils actually work?

Not every soil is right for a rammed earth wall— but our working philosophy at Ramro Mato is that there is no such thing as a useless soil. Every material has a nature, and the question is always whether that nature suits the application.

Ramro Mato means good earth. It is a conditioning of context. It is a way of looking at the material: find the right soil for the right use, rather than forcing an unsuitable material into a role it cannot perform.

For load-bearing (CS)RE walls, we look for clay-rich binder soils with moderate plasticity and good cohesion. Clay is the binding agent — it provides the matrix that holds the wall together once compacted and dried. The character of that clay matters enormously. Expansive clays such as black cotton soil contain montmorillonite minerals that shrink when dry and swell when wet. Same is the condition with bentonite clay. Neither is suitable for wall construction under cyclic moisture conditions. The plasticity index is too high, and the dimensional changes too unpredictable over time.

Those same materials are excellent pond liners — their impermeability, which is a liability in a wall, becomes a direct asset in water retention. We have observed this use in the Kathmandu Valley and Bhaktapur. Each soil finds its place.

What we look for in a CSRE binder soil

Moderate plasticity — enough to bind, not so much as to crack or swell
No significant montmorillonite or expansive clay minerals
Good cohesion in compressed and dried state
Compatible particle size distribution for blending with sand and aggregate
Confirmed by sieve analysis and field tests before selection

06 Mix Design

What does an ideal mix actually look like?

The ideal mix is not a fixed recipe — it is a target. We work toward a dense, interlocked particle matrix in which the clay fills the voids between coarser particles and provides the binding action. Getting there requires reading the actual materials at hand, not applying a formula from elsewhere.

Our mix design process uses Fuller's curve, the Compressible Packing Model, and ideal soil-concrete gradation curves as theoretical frameworks. We map the particle size distributions of the available materials — binder clay, sand, stone dust, aggregate — and configure a blended mix whose combined grading curve tracks as closely as possible to the theoretical ideal. The Proctor test then confirms optimum moisture content and maximum dry density for that specific blend. Trial specimens are cast under site-equivalent compaction energy and tested in compression.

For the Budhanilkantha villa, our laboratory work confirmed an optimum moisture content of 11% and a maximum dry density of 2.282 g/cc for the final blended mix — a well-compacted, stable matrix that went on to perform consistently in the built wall. For the Nagarkot Residence, a theoretically designed blend using locally available clay-rich binder and graded aggregate was validated by UTM compression testing, returning a peak of 13.169 N/mm².

Cement stabiliser is added at ratios determined by target strength and local soil chemistry — typically 4.67% by weight for our standard CSRE mixes. This is not a default figure we apply everywhere. It is confirmed through trial specimens for each project.

07 Cost

Is rammed earth cheap or expensive? What should a client expect?

Both answers circulate — that rammed earth is cheap because it uses mud, and that it is expensive because it only appears in boutique projects. Neither is quite accurate.

In terms of direct construction cost, a completed rammed earth wall — rammed, finished, requiring no plaster or paint — costs roughly the same per cubic foot as a completed brick wall with plaster and paint applied to both faces. The rammed earth wall needs neither. That saving is immediate and real.

The cost breakdown of our wall construction work runs approximately as follows:

Labour

55 – 67%

Materials

17 – 22%

Formwork & Accessories

10 – 15%

Tools & Equipment

3 – 5%

Labour is the dominant cost, and it varies significantly with design. Smaller, more complex wall sections yield around 3 cubic feet per man-day. Long, thick wall sections with well-coordinated teams and efficient formwork systems can reach up to 10 cubic feet per man-day. The design drives the cost.

As a share of total building cost, the rammed earth walling system typically represents 17–25% of the project budget. The rest — foundation, roof, floors, openings, services, finishes — is comparable to any other well-constructed building. This is what our practice has found consistently: a rammed earth building is not a cheap building. It is a building with a different walling system, and that system costs roughly what an equivalent brick and mortar wall would cost.

Where rammed earth builds long-term value

No painting required — ever, for most interior and sheltered exterior surfaces
Reduced heating and cooling loads through thermal mass
No synthetic finishes — no paint chemicals in the interior environment
Walls that do not degrade behind layers of finish — they are the finish
A building that holds its character without cosmetic upkeep

08 Thermal Mass & Comfort

Does rammed earth actually make a difference to comfort inside?

Rammed earth walls are dense. A 350mm exterior wall — our minimum for Kathmandu valley conditions — has significant thermal mass. It absorbs heat slowly and releases it slowly, buffering the interior from the peaks and troughs of the outdoor temperature cycle across a day and across seasons.

The practical experience reported by our clients is consistent: the house feels comfortable. Heating and cooling equipment runs less, or not at all. Rooms do not overheat in the afternoon. The building responds to temperature swings with a lag rather than an immediate transmission through the wall.

Thermal performance is not a wall-alone question. Orientation, window sizing and placement, floor material, and roof insulation all work together with the wall mass. A rammed earth wall in a poorly oriented or over-glazed building will not perform as well as one in a building designed holistically.

350mm

Minimum exterior wall thickness for Kathmandu valley thermal performance

600mm

Maximum wall thickness used, for structural and high thermal mass requirements

≈0

Active climate control reported not needed by clients in well-designed CSRE homes

[ Day Time: High Heat ]

☀️ Sun Exposure

│

▼

┌───────────────────┐

│ Rammed Earth Wall │ ──► Absorbs & stores heat slowly

└───────────────────┘

│

▼

[ Night Time: Low Heat ]

🌙 Cold Air Outside

│

▼

┌───────────────────┐

│ Rammed Earth Wall │ ──► Gradually releases stored warmth indoors

└───────────────────┘

09 Seismic Performance

Will it survive a big earthquake? This is Nepal — the question is not optional.

Nepal sits on one of the world's most active seismic zones. An unengineered earth wall in an earthquake is a liability. An engineered, reinforced CSRE wall in a properly designed structure is another matter.

Every load-bearing CSRE wall we build is reinforced. Vertical HYSD rebars are placed in cross-section — typically two bars positioned approximately 100mm from the exterior face in walls of 450–600mm thickness. Horizontal PP geogrid sheets are laid at regular intervals throughout the wall during the ramming process. The geogrid improves shear resistance and limits crack propagation — the same principle as horizontal reinforcement in engineered masonry.

Structural analysis and design follows NBC 105:2020, Nepal's National Building Code for seismic loading. We model the building computationally, verify inter-storey drift against serviceability limit state requirements per Cl. 5.5.2.1, check torsional irregularity, and size foundations accordingly. The Nagarkot Residence structural report documents this full workflow for a two-storey plus attic CSRE building on a 209 sq m plinth.

Crucially, the structural properties we input — compressive strength, shear behaviour — come from project-specific laboratory and UTM test data, not generic assumed values. The design is grounded in numbers we have measured for that project's materials.

Seismic design approach — our standard

Vertical HYSD rebars, 2 bars in cross-section, 100mm from exterior face
Horizontal PP geogrid at regular height intervals — shear resistance and crack control
Full structural analysis per NBC 105:2020: drift, torsion, base reaction, mass participation
Structural properties derived from project-specific UTM and lab test data
Foundation and connection design integrated with wall structural behaviour

10 Fire Resistance

What happened when rammed earth was tested after a real fire?

The Bagaicha Adventure Resort in Harkapur, Nawalpur experienced a fire during its operational life. After the fire was extinguished, we extracted core samples from the rammed earth walls that had been exposed to heat and had them tested to IS 516 Part 4 (2018).

5.57N/mm²Before fire------->5.56N/mm²After fire

The three post-fire cores returned equivalent compressive strengths of 5.33, 5.18, and 6.18 N/mm², with a mean of 5.56 N/mm². The original mix design cube tests from 2019 had returned a mean of 5.57 N/mm². The difference is 0.01 N/mm².

This is consistent with what earth does under heat: it does not combust, does not melt, and does not off-gas. In a fire, a rammed earth wall behaves more like fired ceramic than like timber or steel. The repair work after the fire involved cleaning the wall faces and patching sections that had been mechanically damaged during the dismantling of the metal structure — not replacing walls that had structurally failed.

One practical note from this experience

If heated rammed earth walls are sprinkled with cold water during firefighting, differential cooling can cause cracking and tilting. Uniform, gradual cooling is preferable where possible.

11 Maintenance

What does a rammed earth building actually need over its lifetime?

Less than most wall types — significantly less than painted masonry.

The walls themselves, once complete, require no painting, no plastering, and no scheduled treatment. Where a wall has been finished with linseed oil or a breathable wax, reapplication every several years is reasonable for exposed surfaces. Unsealed interior walls in normal conditions require nothing.

The most common physical maintenance issue we encounter is corner chipping — at door and window reveals, rammed earth can chip if struck by furniture or goods being moved. This is repairable with a matched earth mix patch, and the repair is most successful when done promptly, before the surrounding surface weathers further and the colour match becomes harder to achieve.

The larger maintenance obligations are building-wide, not wall-specific: keep the roof in good repair, keep drainage clear of the wall base, maintain the damp-proof course. These are the same obligations that come with any well-built building.

12 Aesthetics & Finish

What does a finished rammed earth wall look like — and what are the options?

The most common reaction from clients seeing a completed rammed earth wall for the first time is some version of: is it really done?

It does not look like a smooth, white, putty-painted surface. It is bare, textural, and earth-toned. The layers of compaction are sometimes visible as horizontal strata — a direct record of how the wall was built, layer by layer. The surface has a natural variation that no manufactured finish can replicate, because the material itself is the finish.

This takes some getting used to for clients accustomed to conventional interior finishes. But for those who have lived with it, the response shifts. The wall has a presence that painted surfaces do not.

Finish options we work with

Penetrative hydrophobic sealant — exterior walls; repels water, allows vapour movement, natural earth appearance maintained
Linseed oil — natural, breathable; deepens the earth tone subtly
Breathable wax — interior use; surface protection with a soft sheen
Natural clay-based paint — interior; earth tones; full vapour permeability retained
No finish — interior walls in sheltered conditions; the compacted surface is the finish

One note for construction teams and allied professionals working alongside rammed earth: protecting the wall surface during construction is critical. When RCC ring beams are cast above or adjacent to earth walls, concrete bleed water will enter the surface pores and leave calcium deposits that cannot be removed after setting without visible sanding damage. Tape all junctions before any concrete work. Clean with water only. Prevention is the only effective strategy here.

13 Limitations

When is rammed earth not right for?

Rammed earth can be adapted to almost any project context—it is not an exclusively rural or boutique material, and it is not limited to a particular architectural style. In fact, it is excellently suited for an industrial scale where large volumes of walling are required through efficient, repeatable processes. Rather than seeing certain scenarios as "not right," we view them as opportunities to select the most effective engineering strategy to ensure the material rewards the project.

Optimizing Urban Space: In high-density urban plots where every square inch of floor area is a priority, the standard 450–600mm monolithic wall thickness is often exchanged for a more streamlined approach. For these projects, we can utilize insulated rammed earth panel systems. This allows us to achieve comparable thermal and structural performance at a reduced thickness for the building envelope, while still providing the beauty of raw earth for internal feature walls.
Engineering for the Ground Level: While rammed earth is a high-performance material for the main structure of a building, it thrives best when it can remain clear of permanent subterranean dampness. Instead of using it for below-grade basements or retaining walls, we utilize it for the floors above, transitioning from the foundation with a properly detailed vapour barrier and protective lining. This ensures the longevity of the earthen walls while maintaining the structural health of the building.
The Reward of Meticulous Craft: Rammed earth is at its best when treated as an honest, load-bearing structural craft. The rigorous material testing, precision mix design, and calibrated construction on-site are the very steps that turn an unspecified natural material into a documented, repeatable building element. Since we all value this scientific precision, the process provides total confidence throughout the project and results in a home with unmatched natural aesthetics.

The Philosophy: Rammed earth is always "right" when the construction method matches the project's goals. When we respect the material's nature and engineer it with precision, it rewards the owner with a structure that is both a scientific achievement and a timeless work of art.

phase, the mix design, the care required during construction, the unfamiliar surface — all of it makes more sense when the choice is rooted in what rammed earth is, not just what it looks like.

14 Where to Begin

For someone considering rammed earth — what is the first step?

Rammed earth is the most durable of the earthen building techniques. Engineered properly, a (CS)RE wall performs at the level of first-class masonry, carries a fraction of the embodied carbon of an equivalent RCC wall, uses materials found within practical distance of almost any site in Nepal, regulates indoor humidity, requires no synthetic finishes, and will outlast most of what surrounds it.

It can build an earthquake-resilient, multi-generation home. Not as a promotional claim — as a demonstrated outcome, documented in structural reports, laboratory data, and buildings that are currently occupied and standing.

What we have found, across the projects we have completed — from the Kathmandu valley to cold storage at 3,600m in Mustang — is that the material rewards care at the design and testing stage, and asks relatively little after that.

Our starting point for every enquiry

Bring us your plot location, a preliminary brief, and access to the soil sources you have in mind. We will tell you what is possible, what it will take, and what it will cost — before you commit to anything.

The earth beneath your feet has been building shelter in this part of the world for thousands of years. With the right mix, the right design, and the right team, it still does — and it does it well.

Start with a conversation, not a commitment.

Ramro Mato works exclusively with earthen building design and construction. We work across Nepal — residences, resorts, infrastructure, and research projects.

If you are thinking about rammed earth for your next project, we are happy to talk through the site, the soil, and the possibilities.

Visit ramromato.com.np

Rammed Earth — What We Have Found