Set a height value on an individual CSS Grid row - css

Question

I have a CSS grid layout where I have the top row spanning the entire grid using the grid-column property.
Does anyone know how I can set this row to be 100px high and have all the subsequent rows set to a grid-auto-rows height of 200px?
I know I can input individual values with grid-template-rows for all the specific rows, but there are going to be a lot of divs on the page and don't want to input 100px and then a load of 200px values using this grid-template-rows property.
I'm thinking there must be a way to set individual pixel values on certain rows and then have everything else as grid-auto-rows?
I can't seem to find how to do this in the docs.
Any help would be awesome!
https://codepen.io/emilychews/pen/dZPJGQ
.gridwrapper {
display: grid;
grid-template-columns: repeat(2, 2fr);
grid-auto-rows: 200px;
grid-template-rows: 100px 200px;
grid-gap: 10px;
}
nav {
background: yellow;
}
.gridwrapper div {
padding: 1em;
background: red;
color: white;
box-sizing: border-box;
}
.gridwrapper div:nth-child(odd) {
background: blue;
}
nav {
grid-column: 1 / -1;
}
/*MAKE DIVS 1FR ON MOBILE*/
#media only screen and (max-width: 736px) {
.gridwrapper {
grid-template-columns: 1fr;
}
}
<div class="gridwrapper">
<nav class="grid">1</nav>
<div class="grid">2</div>
<div class="grid">3</div>
<div class="grid">4</div>
<div class="grid">5</div>
<div class="grid">6</div>
</div>

Answer 1

Does anyone know how I can set this row to be 100px high and have all the subsequent rows set to a grid-auto-rows height of 200px?
Yes. Grid can do this cleanly and easily.
First, you don't need to set a height value on the grid item itself. That overrides one of the great benefits of CSS Grid: the ability to control the dimensions of grid items at the container level.
You know that your grid will always have at least one row: the top row. That's your explicit grid.
You don't know how many additional rows there will be. That number is variable and unpredictable. That's your implicit grid.
The grid-template-rows and grid-template-columns properties set track sizes in the explicit grid.
The grid-auto-rows and grid-auto-columns properties set track sizes in the implicit grid.
Therefore, this is probably what you're looking for:
.gridwrapper{
display: grid;
grid-template-rows: 100px; /* top row is 100px in height */
grid-auto-rows: 200px; /* any new rows created are 200px in height */
}
revised codepen

Answer 2

You can use grid-template-rows property.
I guess you are looking for something like this:
https://codepen.io/harora/pen/EbaQxr
Here is a nice reference to the Grid model:
Grid Model Explained