Incremental Housing Strategy by Filipe Balestra
and Sara Göransson



Architects Filipe Balestra and Sara Göransson have developed a strategy to develop informal slums into permanent urban districts through a process of gradual improvement to existing dwellings instead of demolition and rebuilding. Update: this project is included in Dezeen Book of Ideas, which is on sale now for £12.


Developed in Bombay, India, the Incremental Housing Strategy is intended to allow districts to improve organically without uprooting communities.


A pilot project will be implemented in Pune, India but the architects believe the strategy could be appropriate in any country with similar urban conditions.


The architects have developed three house typologies (below) consisting of simple frames that allow for later expansion.


"After creating works for Rem Koolhaas at OMA/ AMO, Neutelings Riedijk, NL architects, and Thomas Sandell, I found it essential to search for the opposite experience: to work for the ones who cannot pay," says Balestra.


See also our story on Quinta Monroy in Chile by Alejandro Aravena


Here's some text, photos and captions from the architects:


In September 2008, architects Filipe Balestra and Sara Göransson were invited by Sheela Patel and Jockin Arputham ( to come to India to design an Incremental Housing Strategy. The strategy had to be implementable anywhere.


Above: implementation collage: kaccha houses incremented and customized

Filipe had previously designed and built a school and community centre in Rocinha, Rio de Janeiro’s largest slum, in a participatory design and construction process together with the locals. The project was called Sambarchitecture and it was documented in a movie which was shown in Cinema Zita in Stockholm during Brazilian Film Festival. This movie was also in exhibition in the Architecture Museum of Stockholm and in Botkyrka Konsthall; Sara has been working on a strategy to connect Stockholm, framing the future urban development as urban bridges between segregated suburbs.


Above: aerial collage: the new archipelago of incremented kaccha houses rising from a sea of well built permanent homes in a typical slum.

Soon after Filipe and Sara arrived to Bombay, a team of international architects, urban planners, landscape architects and graphic designers volunteered to set up the strategy which uses the existing urban formations as starting point for development. Organic patterns that have evolved during time are preserved and existing social networks are respected. Neighbors remain neighbors, local remains local.


Above: Far left: Savita Sonawane from Mahila Milan explaning strategy to slum dwellers of Netaji Nagar. Far right, Filipe Balestra sketching possibilities.

When Filipe and Sara started working they did not know the Indian government would initiate a grant of 4500 euro/ family for the incrementation of their homes at a national scale. The grant is now active and it can be given to any family who lives in a kaccha - an old temporary structure, not suitable for living. It is called City In-Situ Rehabilitation Scheme for Urban Poor Staying in Slums in City of Pune Under BSUP, JNNURM.


Above: informal office in Koregaon Park, Pune

The pilot project will be implemented in Pune, India. Filipe, Sara and SPARC is now spreading the word to implement the strategy in other countries with similar needs: Brazil, Kenya, South Africa, The Philippines, the list is long. 1/3 of the world's urban population is now living in slums.


Above: Life inside a kaccha house I

The strategy strengthens the informal and aims to accelerate the legalization of the homes of the urban poor. The communities are asked to engage with the construction process to customize each house, i.e. each family will paint the house the color they want. After all, who knows better than the people themselves how do they want to live?"


Above:  Life inside a kaccha house II

We developed 3 basic prototypes for the slum dwellers to choose from. These are 3 basic typologies. House A is a two story home, structured like a 3 story home to ensure safety in future vertical extension; House B has Incrementable ground floor, which is left open for either parking or for the family to turn that open space into a shop. House C has an incrementable middle floor, to hang clothes or to be used like a living room. All proposals are for one family and 270 sq foot area (grant regulations).


Above:  Life inside a kaccha house III


Above: Life inside a kaccha house IV

Design team:
Filipe Balestra
Sara Göransson
Guilherme de Bivar
Martinho Pitta
Rafael Balestra
Remy Turquin
Carolina Cantante

SPARC and Mahila Milan





Posted on Tuesday May 5th 2009 at 10:20 am by . Copyright policy | Comments policy

  • SillyBug

    While architectural repetition of certain slum typology certainly brings an improvement step from existing structures, I think this is way away from rehabilitating slums. The reasons slums are slums is not only because of individual building qualities. If you rebuild on spot without uprooting, this means you are not touching one bit on the (non-existent) infrastructure (electrical, water, sewage, excess water drainage, roads etc.) For ex:without standard streets the slums are as unreachable by public service vehicles of any kind, so the quality of life is just as low. Rain water flows into the houses just as much, and “sewage” overflows just as often.

    And what about slums that are built and grow without the proper consideration of topography? How do they effect the climate, ecology etc. of the city by being there? What kind of disadvantages do the people in a slum area live becase that particular area is topgraphically lower than the surrounding region?

    Before architecture, there are many determining factors concerning the well-being of a city and its residents. And slums are cases where these factors have all been neglected in the first place.

  • Jane

    well just check out the number of comments this project has received. As a matter of discourse, this project is far more neccessary and relevant in todays current climate.
    very inspiring work guys. miss you all..hopefully i can join this process one day.
    what a breath of fresh air…

  • Khaild

    I believe that architecture for poor and green architecture will bind human to nature. Great work.

  • texxeen

    interesting work, something i would like to do back i Africa, interesting insight Kim, I lived near some of those slums growing up, they where sH**t, i rarely ventured into them, infact i am certain that any type of improvement would be apprecitated by those who live there. Rem says he loves the slums of Lagos, why doesn’t he move OMA there, and practice slum architecture, cook and drink the same water he ejects diarrhea into me nobody really wants to live there, it’s not a matter of choice, as Matt makes it seem. As long as a project has built in considerations that are significantly tied into local energy flows, natural and local culture in terms of materiality and execution, then i guess it’s ok with me, and it’s appearent that this project is striving for that.

  • texxeen

    btw Favela Barrio is like heaven compared to some of the stuff i’ve seen, they had 2 by 4’s, and electric power tools. Like superpower nations emerging and underdeveloped nations, there are superpower slums, emerging, and slum ass “third world” slums as well. A favela in Brazil is like a superpower slum, while something in Mushin or Ajegunle, is a “slum ass slum”; there are varying levels of slum typologies Matt.

  • I’m a little bit late, perhaps, to contribute to the discussion.

    Anyway, I believe that Matt has good points and that slums need more social policies, social workers, infrastructures, planning, and bla bla bla.

    Nevertheless I think that architecture is asked to contribute with its milieu to the rehabilitation of favelas. It’s true: architecture, perhaps, is the last thing people are thinking to get done.

    But it would mean that architecture is useless. That architecture is just a matter of glossy magazines. That architecture is a leisure for a small elite. …

    Instead i think that architecture has limits and we have to accept those. Also planning, economic, infrastructure engineering, have limits. The solution, if any, is made of a plenty of variables in which also architecture plays an important role (less than have running water, more than have a local Guggenheim, etc)

    Yet we should be a bit patient. Architecture will not change in one year (because we have a global crisis). We have to understand that changes happen gradually. I believe that they will happen gradually by doing and making also mistakes. Then they will affect also the academic curriculum.

    Perhaps in 20 years we will have a better architecture: socially responsible, less selfish, …perhaps something really different from what we get now. we have to wait and doing…otherwise it’s just sterile discussion

    Ad what we get now??? A dutch architect and his friends appreciating the aesthetics and organizational values of slums…nothing more than a selfish and opportunistic interpretation.

    If we wanna change we should also move on …from this opportunistic/generic/junk-like modus operandi to something which is more democratic-like modus operandi

    Yes! democracy is the keyword, in my point of view, for the future Architecture.

    By the way, as group we are working in P2P urbanism. check at this link:
    we would love to have contributes also by you.



  • Jack

    I feel that the whole issue with the informal slums is that governments usually look as this places as an eyesore. Slums are also viewed as places that are breeding grounds for malaria, typhoid and cholera.
    With the introduction of this design, i believe problems such as this could be solved and governments would be able to accept this places as hygenic and acceptable housing estates. This would negate the problems that has caused many slum areas in different countries where the government so commonly seek to clear this areas.
    Furthermore, it would also be beneficial for the people in terms of health and elevation of their land prices, which will eventually lead to growth of the economics and vibrancy of the area.

  • Matt ->
    When I lived in Mumbai for 18 months I walked by two very large slums every day on the way to work (Studio Mumbai Arch). I saw how these neighborhoods are structured in a very complex manner. Talking with the locals, they refer to their slums as their “Village”. They are in fact structured more as villages and towns within the larger city. The truth is that many times, whole villages from the country will re-locate into the city, fleeing the poverty and toil of the farmlands. It is imperative to keep the Village together.

    As it stands now, the current way of slum improvement, is to completely raze the entire village (which always involves riots and violence) and in its place put a large concrete apartment building (see link) that has a completely different structure that cannot adjust to the pre-existing village fabric. By this time, everyone has moved away to another slum farther outside the city, their jobs, family networks, and livelihood completely destroyed. The most common structure of a slum has the family business on the ground floor, either retail, or small industry, and the whole extended family living on the floors above the business. The current redevelopment building simply cannot support this mixed use structure. Whats more is that, the families that were supposed to live in the new housing almost always rent out their space for a profit, while still living on another slum.

    Building these small new buildings would help the government install proper water lines, electricity, and sewer lines, that are very much needed in the center of slums. Most Mumbai slums have electricity and running water (govt donated), most do not have proper sewage perhaps. leading to disease and sickness.
    I also think that painting the building all different colors is a great start, though I’m positive the inhabitants will take over and continue painting and improving for years…
    Keep in mind these laums and their buisnesses are not something small you can backhandedly toy with. Dharavi Mumbai (Asia’s) largest slum (pop. 1 million) has an annual economic output of $650,000,000 a year. ALMOST A BILLION DOLLARS. So to come in, bulldozing and putting in regular apartment buildings would be absolutely stupid, and a huge blow to the city.

    Here are some photos of Mumbai slums, and some redevelopments;

    Typical slum house

    Slum redevelopment sign

    new slum apartment building overlooking and existing slum

  • Cityleft->
    We do need architects to work on this problem, because when we don’t we are left with very insensitive and ignorant city officials building apartment blocks, that ruin the culture of the slum, and destroy the local economy. It takes architects like Filipe Balestra and Sara Göransson to wedge themselves between the local officials, and the local villagers, and say “wait a minute lets figure this out in another way”. Leaving it up to only the locals, or only the officials will not, and has never improved the situation.

    Architects need to be here to mediate this very very complex problem. It is not as simple as building an apartment building and leaving. Riots, and wars are caused by the demolition of slums, it happens all the time in India. Who says that an architects job is to only work for the rich, build museums, and come up with funky designs that are formally original. thats BULLSHIT!! pure BS.

    And to say that the project here is not original, the materials, and form only repeat what has been done earlier is not a valid argument. So what, if its not original, or is not beautiful, thats beside the point completely. It helps address an issue that is very architectural (at its core) and has far greater impacts on the quality of life of many more people then any Bilbao could dream of. To say that an architect is not needed to take care of these problems, is to deny what architecture is altogether.

  • ML

    Brilliant idea! The local culture can only be truly reflected by ppl who actually live in it!

  • from Argentina:

    *Slums* are not what you think
    They are called *villa miseria*.Slum is a very welcome word.
    1. they have no water
    2. no electricity sewers
    4. no bathsrooms
    5. no w.c.
    6. their walls are made of cardboard or pieces of wood from vegetable boxes through which wind blows floors just earth that gets damp in winter
    one window if lucky
    8.illegal electirc connections which are a threat to dwellers
    9.ponds or streams of stagnant water where garbage,dead animals etc.float streets just narrow winding paths beteen huts.Neither ambulances not firemen can get to them.

    Picture the poorest medieval human living in the poorest hut and you’ ll cattch the idea

    ANY architecture is most welcome if it can solve these problems

  • this is the BEST Villa Miseria ,close to my house in the province of Buenos Aires:

  • manhattan beggar

    nice project! i like the colors!
    hope to see more of you guys!

  • manhattan beggar

    i forgot
    are the homes going to be furnished, hired, sold, have running water, electricity… and the garage on the ground floor, will it have an electric door? it’s such a pain to get out of your car when you come home after a long day of begging!

  • This is a good project, and so simple that i wonder why we haven’t thought of it before. Maybe the joy of this lies in the fact that it’s a costed, applicable option.

    Swastik – the point of ‘architecture’ here is not to beautify, but to regulate and help. residents will need expert support, and their aspirations will have to be tinged by reality, because we live in a world of limited resources and limited freedom. Choosing to idealise the ‘vernacular’ is probably not the biggest priority here. May even be an indulgence in the face of a workable practical sensitive and good solution.

  • archcritic

    matt + jones = haterade.

  • G Sarin

    POVERTY PORN – is right! All we need is for western architects to put into words and theories the actions of others, add colours and publish a book/paper…….where would we be without you guys?

  • somu

    A day should come when architects were rated based on their service to the
    down trodden society, developing plans to the slum and lower middle class,
    who actually deserve the service of architects and engineers.

    Teresa, Nightingale etc; became noble just because of their service to the poor.

    being an architect i felt very bad on the negative comments made on a good
    effort made by the designers.

  • Gabriel Mills

    Bewildered by so many negative comments on what seems a very simple, straightforward and sensible minimum change for maximum improvement of miserable conditions in which slum-dwellers are forced to live.

    And if architects aren’t the obvious and best people to deal with ALL the factors involved — including working with and for the community they serve — then our training, skills and attitudes aren’t up to much.

    It was architects who, over 40 years ago, proposed to developing-world city governments that the growth of shanty-towns could and should be civilised for their burgeoning populations by providing a basic grid of services and drainage before people appropriated land, even if nothing more could be publicly afforded.

    270 sq ft per house / family, distributed over three floors, is pitifully small compared with the space standards most of us are used to. But if this is all that is feasible (I notice the grant stipulation) without uprooting entire communities & shifting them to soulless blocks liable to be rented out to others, then this is the way to do it.

    While normally the “applicable anywhere” description would sound warning bells, clearly these simple basic principles are the exception, unless perhaps in earthquake areas. And it has to be assumed that in monsoon areas, the run-off from flat roofs is provided for.

    People do care about colour — especially in situations where few other personal choices can be made. Choice of colour expresses feeling and identity, and helps to act as unique home and (in sequence) “street” location markers in otherwise bewildering miles of similar construction. And paint at least is cheap, compared with construction materials.

    Good for these architects.

  • peixe

    thats an excelent idea, low cost, simple plan, and the location… these people really need the intervention.
    the team is excelent, talented and inteligent people, showing to the world that the portuguese architecture is not only siza vieira and souto moura!

    peace and respect my friends

  • zsa zsa

    Nobody deserves the services of architects.

  • Sagar

    HI Guys,
    This is very interesting discussion between role of architectural typology and social, political, economical issue. I think both sides are fare enough but still not able to solve the problem of informality. I agree with MATT this is not first time such projects is done but at the same time Matt there are lot of the policies made for slums and still they are not able to answer the question of such informality.
    My point is both architecture and the Matts idea of implementation of policies has to worked out simultaneously. Matt the architectural typology plays very important role in socio economical process. that we can see it in most of European cities. The second issue is we need such projects which will help to improve living conditions for slums, but at the same time it should not be gentrification. One of the point mentioned in above discussion about ownership will create the problem of gentrification.

    Few days ago i was reading about Berlin redevelopment in 1900. I think it is very interesting to refer that example to understand the role of architect, planner, socialist working together for issue of informality.

    About the above project i think it is giving some better housing conditions than existing, but this not enough, Providing cheap boxes is not the solution for slums. This is where i agree with Matts point of increasing there economical conditions. How to improve the job conditions, how to improve there local businesses. These issues are totally missing in the proposal.

    Most of the slums in India, specially in Mumbai has lot of local businesses, the new building typology should consider to improve those businesses, like we can see this in Some social Housing in London, I think the above proposal is just a box which will fix the family in fix area, Thts what i understood by looking images of building typology. This is project is not so much different than what we see in most of the slum clearance project.

    Finally i want to say, we need to rethink our tools for issue of informality, we need to understand that just giving house for poor people is not going to help to reduce the poverty but also need to create social economical structure which will create the conditions for help them self…

  • Bartek Klimczak. Registered Architect WA, Australia

    Whilst i agree with some of the comments here that Architects have been in the past egoists, I also find it ridiculous that the Architect bashers here are stating that Architecture today is irrelevant to affordable housing, and that the problems are legal, political and or infrastructure based only. Architects study for 5 years and then train for another 5, we are as close to experts as you will get in this field, it is an Architects job to be innovative, accountable, contextual and also culturally senstive in any outcome be it high or low budget and i think youll find most Architects are rearing for an opportunity to work pro bono in low tech solutions fed up with only getting high end commissions. I have researched countless exampled of NGOS who build stuff without thinking, without engaging Architects where the built outcome is rejected by the local community, engineers, builders and lawyers just dont get it, its not their job to. I think most Architects would be interested in the background occupations of these backyard critics and their qualifications for making the above negative comments. I think this project will be a catalyst in this emerging unprecedented field of drastic urbanisation redevelopment where 1 billion people are in need of help. Yes slum dwellers arent stupid, yes the problems are often about legal rights but slum dwellers also arent experts in construction either, and sometimes proffesional expertise shouldnt be shrugged off either beit local or from abroad. I was personally inspired doing a slum redevelopment university unit studying under Doshi in Amhedabad and having been dieing to find a way to go back and help, and most of the things i learnt where based on eveolving ideas with input from all cultures, Yes local Archtiects probably have more local knowledge but synthesis of eastern and western knowledge is where we may actually achieve a creative innovative outcome. I think sitting back on a golden throne and poking holes in projects that are genuinly trying to make a difference and only referencing the imperial mistakes of the past is naive as it is distasteful

  • matt

    hey you guy that write down your social status as part of your name and spell Architecture with a Capital A, it seems that you know your lesson very well, is it a real copy-paste of your courses or did your courses copy-pasted themselves in your mind?

    i think i’d like to meet you and talk with you about Architecture
    the only reason to justify the Capital A is this song

  • Iniciativa excelente! A humanização da arquitetura é uma das melhores contribuições para melhoria da qualidade de vida e desenvolvimento social. Através de um plano piloto visando a implantação de infraestrutura básica em favelas ou zonas de habitação social de baixa renda, garante-se também prevenção de doenças, mortalidade infantil e outras mazelas advindas da pobreza e da falta de condições de saneamento básico. Eleva-se a autoestima dos habitantes da localidade, levando-os à busca de uma melhor forma de viver. PARABÉNS aos arquitetos e ao seu trabalho.

  • Tay

    Some quotes that kind of summarise my view:

    “But while these well-known professionals are happy to become involve in one or two prominent projects, they cannot be persuaded to work in 10 or 20 cities. It’s understandable that no architect wants to spread themselves across so many projects but, rather, concentrate on a manageable number of projects! But this means that in some other communities, there is no architect to assist from the beginning, and the planning is really very rough. Or they borrow an architect from the municipality – but they are not very creative.”

    “Getting [this kind of strategy] to a national scale means it’s something like a war – there are bombs exploding, people are lying injured all over the place, there’s no time for much fancy footwork. We need architects who can be like doctors on that battlefield, who can do their doctoring in these rough conditions, without all the perfect, sterile conditions and controlled atmosphere of the hospital operating room, with all the support staff. No doctor wants to work in those conditions, but they have to. And it is these kinds of doctors that are needed,” Somsook Bonyabancha

  • Tay

    It is distasteful to see people rejecting the critique made here due to a higher moral status and experience they claim to have. Although the good will of this project is undoubted, it is naive to think that such project will have a long-lasting impact and at a relevant scale.

    Too many people are missing out the complexity and the ambiguity involved in this kind of project. I have little doubt that the architects involved in this project were inexperienced in the development/aid field (they went there without knowing about the 4500 euro grant; how were they gonna fund the project? with the help of SPARC i presume?). When i saw the amount of praises these development amateurs get, I cant help but think that it’s a bit ‘unfair’ (petty me?). I can sense the silent urge of other architects wanting to put their flags in some developing countries; the more impoverished, the better, of course. Somehow it’s kinda sexy to help the poor nowadays.

  • a comment on the project and one on the comments –
    the project – very simple and workable. I have one major criticism: the major driver for informal settlements / slums is people’s proximity to their work. Many people in slums work right where they live. Why not improve this design by ‘zoning’ or ‘designing’ work spaces on the ground floors that have meaningful relationships with the street and are flexible enough to facilitate multiple types of industry / commerce? This strengthens the economic viability of the project.
    the comments – too many narrow definitions of architecture. There are people in this thread who are basically saying that the slum is not the proper domain for ‘architecture.’ What crap. Kudos to this team who are broadening the architects work to include proactive, missional work in domains that have for too long been left out in the cold.

  • J P Bak

    I have with interest studied the often very emotional discussions about the Mumbai project from May 5th 2009 to January 23rd 2010. I am involved in an important housing project in a different part of the world and I wonder, why this extremely important debate suddenly lost everyone’s interest? As things are developing in this world and with the latest financial and environmental disasters one should think that this dialogue could be one of the tools that could keep the momentum in developing the most basic need, shelter for poor and weak against escalating poverty. I would assume that Filipe and Sara’s initiative would be the best platform for such efforts. There is a lot of open questions, what about the stairs in an environment with a lot of handicapped, is just one of them. On a final note I would like to see the modular system in this project expanded with flexible and multipurpose unit

  • GS

    i agree with matt “solving problems in the slums have nothing to deal with architecture”

  • Jordi

    Matt: first of all, let’s not idealize slums. Slum dwellers indeed have a lot of knowledge, but there’s a lot of suffering too, so it is important that something is done about them. Dealing with slums requires a whole lot of expertise, and political will as well. Slums in most cases have problems of all sorts: legal, political, organizational, gender, city-scale development plans, sructurally insecure housing, inadequate water and sanitation infrastructure services, inadequate public transport, unaffordable and unaccessible healthcare and education, environmental hazards, etc. It is reare to find slums dwellers that can sort out theses issues without professional support (including architects). The question is: how this support is planned and carried out; is it respectful, integral, ethical, empowering, etc?

  • Dom

    I've been reading through this whole thing with a degree of apprehension, and a growing imperative to reply. Apprehension because it became more and more difficult to figure out how to respond, because the need to provide a cogent and complete response seemed to grow in tandem.
    I'd hope everyone can agree that the subject of slum life is a complex one; an issue that is as context specific as any. Perhaps on this point, the project in question may have been overoptimistic.
    It's very easy to lose sight of the context of a given project online. Reading the article at first I had in mind the kind of shanty made exclusively of found sheets of stock, while it appears the case might resemble a bit more the Favela de Rocinha, already made largely of bricks, mortar, stones, and with solid floors. In terms of a purely structural framework in the specific cases of the dwellings sited in the article, it may be correct that this project's aesthetic value is rather poorer than the vernacular. But the real question, that's only hinted at is the supply of sewage and water and electricity, and where i suspect the majority of the work would have been over the course of the project. You can't just throw pipes at them, and a real expandable solution has to be found. I don't think it's purely informality we're trying to accommodate here, nor is it simply the need for a progresssion to a more sociably productive structure. The trick is to introduce safer structures and services at meagre costs without destroying the potential strength that can be had from what is in situ, without introducing any of those effects we come across all too often in shelter aimed at the poor that diminish one's sense of self worth. What i find all too frequent is a project thinks itself too clever. If you live in a place like that, you feel cheated, and i think that is the most important thing to keep in mind.
    By providing a solution that is as bare bones as possible with real differences in program potential perhaps that may just work.

  • Johan

    I've read some similiar project by Asian Community for Housing Right (ACHR) in Bangkok and Filipina.. as far as I read, it's work!

  • leperxx

    @ matt & others

    1. totally disagree with frequent patronising and naive attitude towards "poor undeveloped" countries, and the customization argument through colour is just a joke, if not an offence to people's intelligence.

    2. somehow the article is full of pink stereotypes that don't help at all to understand the real and specific situation of these informal urban settlements, nor help the project itself to be analysed in its actual potential value.
    it might be that this initiative has some beneficial outcomes to the community from the social and political side, but these are not correctly explained or detailed in the article – don't forget that dezeen is just a trends magazine therefore information tends to be quite superficial and aesthetics-driven (fair enough though, if someone wants deeper info they should dive into other sources).

    3. in my opinion this is quite a bad example of architecture, poor and simplistic – as i mentioned above, it may have other values out of the discipline- and a low quality parody of v.b. doshi's aranya complex -you can check it out and judge for yourselves:


    What about the toilets? That’s the main concern of these people.

  • sharad mahajan

    I have witnessed the work of Filipe and Sara in Yaravada slums in Pune and appreciate their spirit and keen sense of observation. They paved the way in giving direction to BSUP project under JnNurm.

    Mashal is indebted to them for their input. We completed over 2000 houses under the same project but must mention that the above team did pioneering work which made us achieve what we did.

    Sharad Mahajan
    Ex ED of Mashal