Easy bricks for blocking up fireplace!

[Siderealxxx]

Hi, I have to block up my fireplace (I will be putting in an air vent and the top is already capped).

It's roughly 60 x 70 cm so I will need to cut a good few bricks (including width-wise).

Is there a lightweight brick that will do the job that I can saw by hand?

Thanks in advance

 

[Dereekoo]

Why will you have to cut any bricks, a bolster and lump hammer will be good enough unless the brickwork is part of the visible finish

 

[Siderealxxx]

Bricks won't be visible, will be plastered. I can split bricks width-wise (if I have enough spares for errors), but I will likely get to the top of the opening and need a thinner brick to finish. No idea how to split height-wise with my skill level. I thought there might be something lightweight and easier to work with for novices. Thanks

 

[23vc]

Thermalite blocks

 

[Wayners]

Thermalite blocks
Cut with saw
I have cheated in the past and wedged blocks with a few stones if needed.
It's all a bit loose and can move easy but when dry it's solid.
Just chuck in best you can. Who cares what it looks like. Don't over think it

 

[Siderealxxx]

Thanks yeh Thermalite it is I think!