Pointy Roofs Nina and the Neurons

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-Yeah!

# Nina and the Neurons Find out what you need to know

# Oh, yeah! #

Toot-toot! Hello, lovely townspeople, hello.

Oh, hello!

I'm just playing with my little toy town and, oh,

I've just noticed the roofs aren't on these houses.

We don't want the rain getting in.

BEEPING

I hear a beep, I see a flash, I wonder what they're going to ask.

BOTH: Hi, Nina!

Hi!

We've got a question for you.

Why do houses have pointy roofs?

That's a great question!

Why do houses have pointy roofs?

Well, lots of people live in houses with pointy roofs

but why are they pointy?

Why don't you come down to my workshop and we'll investigate?

-BOTH: See you soon, Nina! Bye!

-Bye.

Well, I'm going to need some help to answer this one

and I know just who to ask.

OK, Neurons, time to get to work.

ALL: Neurons at the ready, Nina.

OK, today's question is why do houses have pointy roofs?

Now, which Neuron do you think will be

most useful in helping us find the answer?

It's Belle!

CHEERING

ALL: Go, Belle! Go, Belle! Go, Belle!

Go, Belle! Go, Belle! Go, Belle!

Brilliant! I'm all ears, Nina.

Today's question is why do houses have pointy roofs?

And because we hear the sound of rain

when it lands on a roof, Belle will be helping us today.

Stand by, Neurons, I've a feeling I may need help from all of you.

I need to get the workshop ready before the experimenters arrive.

Lucas loves tenpin bowling.

Harriet likes horse riding.

But they both want to know, why do houses have pointy roofs?

So today, for one day only,

Lucas and Harriet become the experimenters.

-Hi, guys!

-BOTH: Hi, Nina!

Welcome to my workshop and thank you for your great question,

-why do houses have pointy roofs?

-Yeah.

Lots of buildings have pointy roofs, just like in my little toy town.

But to find out why, let's start with an experiment.

ALL: Whoop-whoop! An experiment! We're ready, Nina!

I have made two dens, each with different roofs.

-So what shape is your roof, Harriet?

-Flat.

-Mm-hm.

-And what about you, Lucas, what shape is your roof?

-Pointy.

It is pointy!

Now, we're going to find out what happens

when it rains onto your different roofs.

It's going to rain onto the flat roof first.

Here we go, Harriet.

SHE GASPS

Oh, no!

LAUGHTER

-Oh, no! What's happening to the water?

-It's staying on the roof.

Yes, because your roof is flat, the water is staying on top of it.

Nina! The roof's beginning to sag.

That's right, Felix, the roof is bending because the water's

on top of it.

Now, you see, water is actually very heavy.

Two buckets of water weigh nearly as much

as one of you experimenters.

Wow! That is heavy!

Because the rainwater stayed on top,

it made a puddle and made the roof sag in the middle.

Now, let's see what happens when it rains onto the pointy roof.

LAUGHTER

Oh, ha-ha-ha! So, what's happening to the water this time?

It's sliding off.

Yes, because this roof is pointy,

the water runs down rather than collecting on top.

And with no heavy water lying on top,

the roof won't sag even if it rains all day.

But, Nina, some buildings have got flat roofs.

Ah-ha! Now, most buildings that look like they've got flat roofs,

actually have a very slight slope.

So the rain runs down the slope, into a pipe and then drains away.

So buildings have pointy roofs to let rainwater run off.

Because water is heavy, if it stayed on a roof, it would make it sag.

That's right, Neurons.

-How do they make the roofs pointy?

-That's a great question.

How do the builders make the pointy shape?

Well, I think we need to go somewhere with lots

of pointy roofs to find out.

I wonder where Nina is taking us.

She said we were going somewhere with lots of pointy roofs.

-Tents have pointy roofs, maybe we're going camping.

-Camping!

We can have a campfire and sizzle sausages. Yippee!

I don't see any tents, Neurons,

but I do see a lot of pointy roofs.

OK, so far we've found out that buildings have pointy roofs

to let the rainwater run off them.

But now we want to know how pointy roofs are made.

So we've come here to this building site.

Remember, never go onto a building site on your own.

They can be very dangerous.

That's right, Felix, we've got special permission to be here

but you should never go into a building site without a grown-up.

Now, experimenters have a look over there.

-Can you see the pointy roofs that they're building?

-Yes!

Just look at all the beams in that big pointy roof.

-It looks like a triangle.

-Yes, it does look like a triangle.

There are beams across the top and there's a beam across the bottom.

This beam across the bottom is very important.

Let's do an experiment to find out why.

You've both got the walls of a house and I've got

different-shaped roofs. One here has the beam underneath it.

Lucas, that's for you.

This one does not have a beam underneath it.

Harriet, that's for you.

Let's see what happens when you put your roofs onto your houses.

Harriet, you go first.

Very good. OK, now, Lucas, it's your turn.

Harriet, you can help.

OK, now, Harriet, what's happening to your walls?

They're bending.

Yes, the walls are bending.

So when this roof rests on these walls,

its weight pushes down and out, which makes the walls bend.

Now, Lucas, what about yours?

Have a look at your walls, what's happening?

They stayed straight.

Yes, the walls on your house are not bending and that's

because when the roof with the beam rests on the walls,

its weight does push down but the beam stops

the roof from pushing out, so the walls stay straight.

And real roofs work in the same way.

They're built with beams across the bottom to make a triangle.

The bottom beams stop the roof from pushing out,

which helps the roof to keep its shape.

-What are those?

-Oh, great question!

Those are roof tiles and builders put them

on the roofs to stop water getting in.

In fact, let's go back to the workshop to find out how they work.

So your question was, why do houses have pointy roofs?

So far we've discovered roofs are pointy to let the rain

run off them and they have beams to help keep their shape.

Builders cover the roofs in roof tiles.

But now we want to find out how they work.

So I've got some tiles here.

Now, this is a slate tile.

-So what does it look like?

-Flat.

-Yes, it is flat.

And this tile is made of special concrete and what does it look like?

-Wavy.

-That's right.

So tiles can all look different but they all have to be waterproof

so that water can't get through them.

Oh, I like the sound of that,

waterproof.

Let's do an experiment to find out how waterproof tiles fit

together to make the whole roof waterproof.

So we've got two pointy roofs here

but they're not quite finished, are they?

-BOTH: No!

-Hee-hee-hee!

No, I think we need to add some more tiles.

This roof here has tiles that are next to each other,

they're not overlapping at all.

And your roof has tiles that are overlapping like this.

A bit like fish scales.

-So shall we finish tiling our roofs?

-BOTH: Yes!

Okey-doke, let's get building.

Next one.

-Last tile!

-Thank you!

Well done! These roofs look fantastic.

Oh, no! But it's about to start raining!

Oh-ho! There you go, Harriet.

Go!

That's it!

Wow! That was a lot of rain.

OK, so let's have a look and see if our roofs were waterproof.

What about yours, Lucas? Let's have a look. Oh, dear.

This roof didn't stop the water getting in and that's

because the tiles are next to each other.

They don't overlap so the water got in through the joins.

Now, let's have a look at the roof with the overlapping tiles.

Huh! It is much drier!

The water couldn't get in through the joins because there's

another tile underneath, so the water just drained off.

Roof tiles need to overlap because if they don't,

they'll let the water in. Eugh!

That's right, Neurons.

Roof tiles need to overlap to make

sure the rain can't get through them.

# Nina and the Neurons. #

So your question was, why do houses have pointy roofs?

And I think we've answered it.

Lots of houses have pointy roofs so the rain runs off.

Because water is heavy, if it stayed on a roof, it would make it sag.

Builders put beams under the roof to hold it in a pointy shape.

The beams stop the roof from pushing out and keep the walls straight!

Builders cover the roofs with tiles that overlap

so no splishy-splashy rain gets inside.

So I hope that's answered your question.

BOTH: Thanks, Nina. Bye!

You are welcome. Bye!

If you want to know more about the science around us go to the

Nina section on the CBeebies website.

Have fun!

# Super structures Super structures

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And remember, there are super structures everywhere.

Whether they're big or small, wide or tall, we can all get building.

See you again soon. Bye!

# Nina and the Neurons. #

ALL: Bye! Get building!