Waterproof roof?

This is a simple, but fun activity that even very young children will enjoy. I did it with my 3,5 and 7 year old and they loved it, especially when it came to making it ‘rain’.

Before starting we spent a few minutes talking about what we expected to happen and how we could make the investigation a fairer test.

We decided that the roof tiles would be the most waterproof, followed by the sticks and then grass. However we did discuss that it would depend on how many sticks and how much grass we used and that it would be hard to make the comparison fair.



LEGO house

Roof materials – we used LEGO tiles, sticks and grass

Water sprayer


Place your chosen roof onto the house and spray water on top. We used a set number of sprays to make it a fairer test.

Record any moisture inside the house.



As predicted the roof tiles kept the inside of the house dry, the grass let some water in and the sticks were also waterproof.

lego house


To improve the accuracy of this investigation we decided what we should have done was use grass, sticks and tiles up to a certain hight above the top of the house and kept that constant for all conditions.

Recording the amount of moisture inside the house was difficult. Perhaps if we’d placed paper inside and changed it for each condition we could have compared the dampness of each piece.

Can you think of any other improvements?

More LEGO posts

15 Fun ideas for Science with LEGO

More Waterproofing posts

How waterproof is it?



Author: Emma Vanstone

Science Sparks, is a site dedicated to making Science fun for kids. I’d love you to follow me on my Google Profile+.

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  1. I like the way this got you thinking not only about how to test the different materials, but how to create a fair and accurate test – great problem solving activity!
    Almost Unschoolers recently posted…Ice Cube Roman ArchMy Profile

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  2. Great idea for an experiment. I was thinking of making a “water level gauge” inside to measure moisture and putting a paper towel square inside to see if it gets wet at all. Thanks for sharing with After School Link Up.
    Natalie PlanetSmartyPants recently posted…The Week In Review–May 31, 2014My Profile

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