STRUCTAENGINEERING
Engineer surveying a residential site in Sri Lanka

A-00 / Process

What is house design?

House design is not one drawing. It is fifteen of them — each answering a question the next one depends on, from the shape of your land to the marks a builder sets out on the ground.

Introduction

Building a house in Sri Lanka means satisfying three audiences at once: your family, your local authority, and the people who will actually build it.

Each of those audiences needs different information. Your family needs to understand how the home will feel. The Municipal Council, Urban Council or Pradeshiya Sabha needs proof that the design respects building lines, setbacks and ventilation requirements. Your contractor needs dimensions precise enough to build from without guessing.

House design is the process of producing all of it — in an order where each stage answers a question the next one depends on. Skip a stage and the cost usually appears later, on site, when changing your mind is expensive.

The stages below are how Structa runs a residential set. Which of them apply to your project depends on the package you choose.

Site & layout

Site inspection

Every design decision starts with the land, not a floor plan.

Before anything is drawn, an engineer visits your land. The visit records the shape and levels of the plot, the position of the access road, where the boundaries actually sit, and how the ground behaves — soil condition, drainage, and how water moves across the site during heavy rain.

This visit also establishes the things that quietly govern the design later: which direction the afternoon sun arrives from, where the prevailing breeze comes from, which neighbouring windows overlook the plot, and how far the building line and street line set the house back from the road.

Designing without this information means designing twice. A layout that ignores a slope, a high water table or a restrictive frontage will be redrawn once reality arrives.

House Planning & Design
Site inspection — example from a Structa drawing set. Tap to enlarge.

House layout sketch

Room positions, circulation, light and ventilation resolved in plan.

The layout sketch is where your home takes shape. Room sizes and positions, the relationship between living, dining and kitchen, bedroom privacy, and the way people move through the house are all worked out here — along with door and window positions.

For Sri Lankan homes this stage does most of the work on comfort. Cross-ventilation, shaded openings, the position of the kitchen relative to prevailing wind, and protection of living spaces from direct western sun are decided in plan, long before any 3D view exists.

Expect this stage to iterate. It is far cheaper to move a wall on a sketch than to discover the problem in a 3D view, or on site.

House Planning & Design
House layout sketch — example from a Structa drawing set. Tap to enlarge.

Vastu

Traditional orientation principles, applied where the client wants them.

Many Sri Lankan homeowners want the design checked against Vastu principles — the orientation of the main entrance, the position of the kitchen and master bedroom, and the placement of water and heat within the plan.

Structa treats this as a client preference rather than a fixed rule. If Vastu matters to you, tell the team at the layout stage. It is straightforward to accommodate while the plan is still fluid, and disruptive to retrofit once the structure and services are coordinated.

Where Vastu guidance conflicts with site realities such as road access or sun path, the team will show you the trade-off rather than quietly picking one.

House Planning & Design

Design & approval

House 3D exterior design

The outside of your home, tested in three dimensions before you commit.

Once the plan is settled, the exterior is developed in three dimensions — massing, roof form, window proportions, boundary treatment, and the materials and colours of the façade.

A 3D view is not decoration. It is the first point at which most homeowners can genuinely judge whether the house feels right: whether the porch is generous or mean, whether the roof overhang shades the windows, whether the proportions of the upper floor sit comfortably on the lower one.

Changes here are still inexpensive. Once construction begins, the same change involves material already bought and work already done.

Architectural Design & 3D Visualisation
House 3D exterior design — example from a Structa drawing set. Tap to enlarge.

House 3D interior plan

Living spaces, kitchen and bedrooms visualised room by room.

Interior visualisation carries the design inside — living and dining arrangement, kitchen layout and worktop heights, built-in storage, staircase treatment, and the finishes and lighting of each principal room.

This stage frequently changes the electrical drawing that follows. Seeing where a sofa, television or dining table will actually sit is what tells you where sockets and light points genuinely need to be, rather than where they are habitually placed.

It also settles the decisions that are painful to defer: whether the kitchen is open or closed, how much storage the family needs, and where daylight lands during the day.

Interior Design

House council approval plans

The drawing set your local authority requires before you can build.

No house can legally be built in Sri Lanka without approval from the relevant local authority — the Municipal Council, Urban Council or Pradeshiya Sabha covering your land, and in some areas the Urban Development Authority as well.

Approval drawings must demonstrate compliance with the requirements that apply to your plot: the street line and building line, the space left at the rear and sides, permitted floor area relative to plot size, and the natural light and ventilation provided to habitable rooms.

This is the stage where designing without site information becomes expensive. A layout drawn without regard to the building line will be rejected, and the redesign delays everything behind it.

BOQ, Approvals & Documentation
House council approval plans — example from a Structa drawing set. Tap to enlarge.

Engineering

Structural plans

Foundations, columns, beams and slabs — the part you never see.

Structural drawings specify what holds the house up: foundation type and depth, column positions and sizes, beam layouts, slab thicknesses, and the reinforcement detailing for each.

Foundation design responds directly to what the site inspection found. Soft ground, a high water table, filled land or a sloping plot each demand a different solution, and the difference between them is significant in both cost and safety.

Because Structa began as a structural engineering practice in 2017, this coordination runs alongside the architecture rather than after it — so column positions land inside walls instead of the middle of your living room.

Structural Engineering

Electrical drawings

Every point, circuit and light position, fixed before walls close.

The electrical drawing sets out socket and switch positions, lighting points and their switching arrangement, the distribution board location, circuit design, and provision for air conditioning, water pumps and hot water.

It should be read against the interior layout. Points positioned around furniture that was actually planned are the difference between a house that works and one that needs extension cords in every room.

This drawing has a deadline built into it: once walls are plastered and floors are laid, moving a point means breaking finished work. Decisions made here are cheap; the same decisions made later are not.

Electrical & Plumbing Drawings
Electrical drawings — example from a Structa drawing set. Tap to enlarge.

Plumbing drawings

Supply, waste and fittings routed before concrete is poured.

Plumbing drawings cover incoming water supply, tank positions and pump arrangement, hot and cold distribution, and the waste and soil routes carrying water away from every fitting.

Getting the routes right early matters because much of this work is buried. Pipes cast into slabs or chased into walls are not easily rerouted, and waste runs in particular need consistent fall from the fitting to the point of discharge.

Coordinating plumbing against the structural drawing also prevents the common site conflict of a waste pipe meeting a beam exactly where it needs to pass through.

Electrical & Plumbing Drawings
Plumbing drawings — example from a Structa drawing set. Tap to enlarge.

Storm water drainage plan

Where monsoon rain goes, planned rather than discovered.

The storm water plan handles rainfall: roof gutters and downpipes, surface drainage across paved areas, soakage arrangements, and the connection to the road drain or discharge point serving your property.

In Sri Lanka's monsoon this is not a minor drawing. A house that sheds water toward its own foundation, or toward a neighbour's boundary, creates damp, settlement and disputes that surface years after the builder has gone.

Ground levels around the house are set here too, so that finished floor level sits safely above the surrounding ground and water runs away from the building rather than toward it.

Electrical & Plumbing Drawings
Storm water drainage plan — example from a Structa drawing set. Tap to enlarge.

Documentation

Bill of quantity

What the house is made of, measured and priced.

A bill of quantity measures every material and item of work the house requires — concrete, steel, blockwork, roofing, finishes, fittings — and prices them into a document you can budget and tender against.

This is also the document banks ask for when financing construction, which is why it appears in Structa's packages as a Bank BOQ. Without it, a loan application usually stalls.

Its second use is control. With a measured BOQ you can compare contractor quotations against the same scope, and you can tell during construction whether what is being claimed matches what was priced.

BOQ, Approvals & Documentation

Door and window schedule

Every opening numbered, sized and specified.

The schedule lists every door and window in the house with a reference number, its dimensions, the material and finish, the direction it opens, and its glazing and ironmongery.

It exists so that nothing is decided by assumption on site. Openings are formed in blockwork long before doors and windows are ordered, and a mismatch between the two is a common and entirely avoidable source of delay.

It is also the practical basis for quoting joinery and aluminium work, since suppliers can price from a schedule instead of measuring a half-built house.

BOQ, Approvals & Documentation

Bathroom detail drawings

The most detail-dense rooms, drawn properly.

Bathrooms carry more decisions per square foot than any other room. These drawings fix fixture positions, the heights of showers, mixers and accessories, floor falls toward the drain, waterproofing extents, and how tiling meets each fitting.

Detailing them in advance prevents the familiar results of deciding on site: a shower mixer at an awkward height, a floor that pools water away from the outlet, or a tile pattern that dies into a fixture at an ugly angle.

Waterproofing in particular is worth drawing rather than describing, because failures only reveal themselves once the room is finished and in use.

Interior Design
Bathroom detail drawings — example from a Structa drawing set. Tap to enlarge.

Tile layout drawings

Setting out tiling so cuts fall where they should.

A tile layout sets the starting point and grid for each tiled area, so that cut tiles land in discreet positions rather than in the middle of a doorway or against the most visible wall.

It also quantifies the work. Knowing the layout means knowing the tile count and wastage before ordering, which avoids both a shortfall mid-installation and a stack of unused boxes afterwards.

The visual difference between tiling that was set out and tiling that was improvised is obvious in a finished house, and it costs nothing extra to plan.

Interior Design

Setting out plan

Transferring the design accurately onto the ground.

The setting out plan gives the dimensioned positions needed to mark the building on the actual site — grid lines, column and wall positions, offsets from boundaries, and the finished floor level relative to the road or a fixed reference point.

This is the drawing that connects everything preceding it to physical ground. An error here propagates through the whole build: a house set out a few inches off can encroach on a setback, and discovering that after the foundation is cast is a serious problem.

It is the last drawing of the design stage and the first one the builder uses, which is why Structa includes it in the complete package.

BOQ, Approvals & Documentation

Conclusion

Every stage exists because someone once skipped it.

House design rewards attention early and punishes it late. A wall moved on a sketch costs nothing; the same wall moved after the slab is cast costs weeks. Understanding what each drawing is for is what lets you judge whether a quotation is complete — and what you are actually being asked to pay for.

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Common questions

House design, answered

How long does the house design process take?

It depends on the scope of your home and how quickly decisions are made, but the layout and approval drawings are typically the longest stages because they involve both your input and the local authority's timeline. Structa confirms a schedule after the site visit, once the size and complexity of the house are understood.

Do I need all fifteen steps?

Not necessarily. Approval drawings and structural plans are essential for any home you intend to build legally and safely. Items such as tile layouts, bathroom details and setting out plans add precision and reduce decisions made on site, which is why they sit in the more complete packages rather than the entry-level one.

Can I start construction before council approval?

No. Building without approval from your Municipal Council, Urban Council or Pradeshiya Sabha exposes you to enforcement action and creates problems when selling or mortgaging the property later. Approval drawings should be submitted and cleared before construction begins.

What happens if my land is sloping or has poor soil?

That is exactly what the site inspection is for. Sloping ground, filled land, a high water table or soft soil each change the foundation design and sometimes the layout itself. Identifying this at the start is far cheaper than discovering it once the foundation is being cast.

Does Structa handle the council approval submission?

Structa prepares the approval drawing set required by your local authority as part of every design package. Speak to the team about the submission process for your specific council, since requirements vary between authorities.

Can the design be checked against Vastu?

Yes. Tell the team at the layout stage if Vastu matters to you. It is straightforward to accommodate while the plan is still being developed, and much harder to apply once the structure and services have been coordinated around a fixed layout.

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