When it comes to dividends it’s hard to beat the shares of Westpac Banking Corp (ASX: WBC) and the other big banks. But as a lot of investors already have exposure to these shares, I believe looking outside the banking sector for income is a wise move in order to maintain a diverse portfolio.

Currently on the S&P/ASX 200 (Index: ^AXJO) (ASX: XJO) there are three shares which I feel could provide income investors with growing dividends that are perfect for a retirement portfolio.

Coca-Cola Amatil Ltd (ASX: CCL)

The Australian consumer staples giant has grown its dividend by an average of 3.3% per annum for the last 10 years. If Coca-Cola Amatil grows its dividend at the same rate in FY 2016, its shares would provide a 75% franked 5.5% dividend. Although many investors may have concerns on its future due to the fact that consumer habits may shift away from sugary drinks, I believe Coca-Cola Amatil’s wide range of products and fantastic distribution network will allow it to continue to grow steadily for many years to come.

G8 Education Ltd (ASX: GEM)

The shares of this leading childcare operator are expected to provide an estimated fully franked 6.8% dividend in FY 2016 according to CommSec. The forecast 25.5 cents dividend would make it an incredible seven consecutive years of dividend increases for this rapidly growing company. G8 Education’s management believes there is an addressable market of around 4,000 centres in Australia. With the company owning 471 centres currently, I believe there is still a lot more growth left to come for investors. The shares are currently changing hands at just under 15x trailing earnings following a 9% decline in the last 30 days. This could make it a great entry point for buy and hold investors in my opinion.

National Storage REIT (ASX: NSR)

National Storage is one of Australia’s leading owners and operators of self-storage units. Its shares currently provide a 5.3% dividend which I believe can grow steadily over the next few years. Following a recent acquisition the company will soon have a total of 105 storage centres in its arsenal, making it the largest self-storage operator based on centre numbers. This bodes well for future growth in my opinion, as storage demand in Australia has grown by 2.3% per year for the last five years and looks set to remain steady in the years ahead according to research by IbisWorld.

Finally, if you're looking for even more great dividend ideas then I would suggest taking a closer look at these three fantastic new breed blue chip shares. Each pays a solid fully franked dividend and I feel they could provide share price gain in the months ahead.

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Motley Fool contributor James Mickleboro has no position in any stocks mentioned. The Motley Fool Australia has no position in any of the stocks mentioned. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy. This article contains general investment advice only (under AFSL 400691). Authorised by Bruce Jackson.