Standard Bricks: Holes or No Holes?

Step 2 of the oven build, it’s says standard brick with high temp mortar. My guess is these bricks don’t get too hot? So our builder saved us a couple of pallets of our house brick as we have been planning this for 3 years! However our bricks have holes in them. Is this an issue for retaining heat? Also the end bricks probably should be solid but we don’t have solid bricks, so I’m thinking about mortaring the holes for the end bricks unless someone thinks I should mortar the holes on on all bricks for steps 2-4. What a fun build this has been! Thanks for any insights on this matter.

It should not be. These bricks are a frame for the hearth, but heat rises, and the firebrick in the hearth proper will tend to refract heat back up into the oven. Any convection should be minor, because your oven walls rest over the firebrick margin, so there’s no flame on the hearth border.

If you are applying a veneer to the sides of the bricks, as many do, then you should be fine with mortaring just the holes on the four bricks that face outward. This is the front and rear rows; the side rows will have no faces visible at all. Once you veneer, only the “sides,” oriented toward the top, will be visible anyway.

The holes aren’t going to affect heat retention significantly (see above). They will lighten the load a bit on the edges of your slab. Buttering a bit into those holes will improve adhesion of the mortar, but filling them up completely sounds to me like a waste of mortar.

How great is that, that you have new brick that matches what the builder used for your house?

Hope this helps, Mark, and good luck!

DocM, we were in the same situation, saving extra bricks from our home construction and then using them to build our pizza oven/outdoor fireplace. We opted to mortar-in just the holes of the corner bricks. We didn’t see any need to fill in the holes of the other bricks. If I can figure out how to attach it, I’ll include a photo of our oven. While we may still add some adornments and maybe cover the bare concrete sides, the oven itself has been in use since November 2018 and performing well. No problems with the bricks whatsoever. Buona fortuna!

As Matt stated, the edge brick (w/ or w/out holes) have zero effect on the heat retention - so don’t even worry about that. And as Matt mentioned - you are VERY fortunate that you have matching bricks! Many brick colors / blends have a limited run (like carpet colors / styles).

So what’s up with the holes? More and more manufacturers are starting to put 2 or 3 holes in their standard size bricks as it reduces manufacturing / materials costs (but new brick molds cost around $25K 30K each). It also reduces shipping / fuel charges as each pallet of brick is lighter in weight (over the years - the fuel savings for brick mfgs can really add up).

Here are 2 suggestions that we are going to add to Directions 2.0 in the near future:

Lay about 2’ of aluminum foil on your driveway then place 5 or 6 of the edge bricks on the ground w/ the holes facing up. Fill the holes w/ mortar and allow them to cure / harden for about 24-48 hours. This way, the mortar is perfectly flat / smooth (and dry) when you are ready to install them. If you try putting a large amount of wet mortar into the holes of a vertically set brick - that mortar will start to settle into a blob due to something we like to call “gravity”.

This is a cool little trick I learned on my first masonry job way back in the day… If you have access to a brick saw / tile saw - grab one of your darkest (but colorful) bricks then proceed to cut that brick in random areas. After a several cuts - you will notice that you have a lot of brick DUST. Take that brick dust and put it in a disposable cup.

Go back to bricks that are on the ground and fill the holes w/ mortar - But don’t fill the top 1/2".

Add a tiny bit of mortar to the cup of brick dust, add water - then mix into a paste. Then fill the top 1/2" of each brick w/ that brick paste and allow to dry. After a day or two, that dark brick dust (with the light color mortar) should dry into a smooth / color-matched brick that you can use on the corners of your pizza oven base.

Thank you everyone for the advice. This is a great forum to have. Until next time . . .


We also used bricks with holes in them. If you zoom in on the corner you can see we cut 45,s on the corner bricks, to hide the whole’s. It took a little more time, and layout but it worked well for us.

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