What is the difference between interior and exterior paint?

Exterior paint has more binder so it stays flexible as the wall heats and cools, more pigment so the sun does not fade it, and additives against mould. Interior paint has none of that because it does not need it.

Can I use interior paint outside in Dubai?

No. It will chalk in the sun, crack as the wall moves, then peel. You end up scraping it back and doing the job again, which costs far more than buying the right paint.

Why does exterior paint cover less per litre?

It is thicker and it goes on a rougher surface. Interior emulsion is usually 10 to 12 square metres per litre. Exterior is usually 7 to 9.

How often should a villa be painted outside in the UAE?

It depends on the sun and how close you are to the sea. A good exterior paint on a properly prepared wall lasts several years. Walls facing the afternoon sun always go first.

What colour lasts best outside here?

Lighter colours. They reflect more heat, so the wall moves less, and fading is much less obvious. Strong dark colours in direct sun fade fastest.

When is the best time to paint outside in Dubai?

The cooler months, roughly November to March. In summer a wall in direct sun is too hot for paint to dry properly, and the surface skins before it can be levelled out.

Interior vs Exterior Paint Calculator

Inside wall area

All the internal walls and ceilings added up.

Inside coats

Inside coverage

m2/L

Interior emulsion is usually 10 to 12.

Outside wall area

All the outside walls, including any boundary wall.

Outside coats

Outside coverage

m2/L

Exterior paint is usually 7 to 9.

Tin size for both

Your answer

Paint for the whole job

85 litres

Buy them as two different products, not one.

Interior paint: 40 L, so 3 tins
Exterior paint: 45 L, so 3 tins
Inside area over all coats: 440 m2
Outside area over all coats: 360 m2
Litres per square metre outside: 0.25 L

Interior and exterior paint are different products. Do not buy one drum and use it on both sides of the wall.

Interior and Exterior Paint Calculator for the UAE

This tool works out both sides of a job at the same time. Inside walls on one side, outside walls on the other, each with its own coverage and its own number of coats.

They need to be worked out separately because they are different products. Exterior paint is thicker, it covers less per litre, and outside walls are rougher, so the same area needs more paint outside than in.

If you are painting a whole villa, this gives you one total for the job instead of two sums you have to add up yourself.

What makes exterior paint different

They look similar in the tin. They are not the same thing, and the difference is what happens to them over time.

Interior paint is made to look good and clean easily. It lives in a room where nothing much happens to it: no rain, no direct sun, and a fairly steady temperature.

Exterior paint is made to survive. It carries more binder so it stays flexible, more pigment so the sun does not bleach it, and additives that stop mould and algae growing on it.

Flexibility is the important one. An outside wall in Dubai gets very hot in the day and cools at night, and it expands and shrinks a little each time. Interior paint is too brittle for that. It cracks, then water gets behind it, then it peels off in sheets.

Why the same area needs more paint outside

Two reasons, and they stack up.

The paint is thicker
Exterior paint carries more solid material. A litre of it does not spread as far, which is why coverage drops from around 11 square metres per litre to around 8.
The surface is rougher
Outside walls are usually rendered or textured. A rough surface has far more real area than its flat measurement, so it swallows more paint.
The sun dries it fast
In UAE summer heat paint skins over quickly. Painters have to work in smaller sections and go back over edges, which uses a little more.
Wind and dust
On a breezy day some of the paint never reaches the wall, especially when spraying.

What Dubai weather does to outside paint

This is the reason exterior work here is not the same as exterior work in a mild climate.

The sun is the first problem. Strong UV breaks down the binder in the paint and fades the colour. Dark colours fade fastest and get hottest, which is one reason so many villas here are white, cream or sand coloured.

Heat is the second. A wall in direct afternoon sun gets far hotter than the air, then drops many degrees overnight. The wall moves a little every day. The paint has to move with it.

Salt is the third, near the coast. Salt in the air gets into small cracks and pushes the paint off from behind. It also attacks any metal, which is why railings and gates need their own primer.

Dust is the fourth and it is constant. It settles on everything. A wall that has not been washed before painting gets a coat of paint sitting on a layer of grit, and it lifts off in a year.

None of this is a reason to worry. It is a reason to use exterior paint outside, wash the wall first, and not to try painting in the middle of a July afternoon.

Can you use one paint for both

People ask this to save money, so it is worth a straight answer.

Using exterior paint inside works. It is not a problem technically. It costs more, it often smells more, and the finish choice is narrower, so most people do not. But nothing bad happens.

Using interior paint outside does not work. It will look fine for a few months. Then it starts to chalk under the sun, then it cracks as the wall moves, then water gets behind it and it peels.

The failure is worse than never painting at all, because now the wall has to be scraped back before it can be done properly. That is days of work that would not have been needed.

So the honest answer is: one direction is a waste of money, the other is a job you have to redo. Buy the right one for each side.

Planning a whole villa

If you are doing inside and out together, a few things save real time and money.

Buy drums, not gallons
On a villa you are into tens of litres. The 18 litre drum is much better value per litre, and you will use it.
Buy each side in one go
Tins from different batches can vary very slightly in colour. On a long outside wall in full sun, a batch join can show.
Do the outside in the cooler months
Between about November and March the wall temperature and the drying time are both much friendlier. Summer exterior work is possible but slower and harder to get right.
Wash before you paint
Outside walls here carry months of dust. Painting over it is the most common reason exterior paint fails early.
Fix the cracks first
A hairline crack in render will open again through new paint. It needs cutting out and filling before anything else.

Questions people ask

What is the difference between interior and exterior paint?: Exterior paint has more binder so it stays flexible as the wall heats and cools, more pigment so the sun does not fade it, and additives against mould. Interior paint has none of that because it does not need it.
Can I use interior paint outside in Dubai?: No. It will chalk in the sun, crack as the wall moves, then peel. You end up scraping it back and doing the job again, which costs far more than buying the right paint.
Why does exterior paint cover less per litre?: It is thicker and it goes on a rougher surface. Interior emulsion is usually 10 to 12 square metres per litre. Exterior is usually 7 to 9.
How often should a villa be painted outside in the UAE?: It depends on the sun and how close you are to the sea. A good exterior paint on a properly prepared wall lasts several years. Walls facing the afternoon sun always go first.
What colour lasts best outside here?: Lighter colours. They reflect more heat, so the wall moves less, and fading is much less obvious. Strong dark colours in direct sun fade fastest.
When is the best time to paint outside in Dubai?: The cooler months, roughly November to March. In summer a wall in direct sun is too hot for paint to dry properly, and the surface skins before it can be levelled out.

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