Hello again. So now that I have managed to have a level base I need to crack on with the rest of the plinth. This for me was another first as I have never really done any brick laying or mortar mixing. Again I will be relying on my nice level base to help compensate for how my brick laying may turn out. Turns out if you follow the instructions and keep your patience the large blocks aren’t too bad to lay.
I used large blocks for two reasons:
- The blocks are big and strong, if they can support my house and roof then a pizza oven will be fine
- The blocks are big so less chance of having wonky brick laying…(less brick laying in general)
Plinth Build – Calculations for ordering all the bits
After doing some simple maths and knowing that the Celcon blocks were 440x215x100mm I realised that some plinth walls with 4 layers of blocks would be ~900mm tall and I wanted my plinth (pizza oven base) to be about 1000mm off the ground. A few more calculations showed me that 2.5 blocks would give me a wall length of 1100mm.
I decided that there was no benefit to doing tricky corners so planned to do three straight strips of bricks. ( I really wasn’t looking forward to laying bricks) In order to add some sort of support and back to the pizza oven plinth I also put a tower of four blocks in between the three mini walls. I would leave gaps to allow air flow and drainage as I plan to put wood in the spaces and don’t want water pooling under the pizza oven plinth.
The main plinth which would be placed on top of the Celcon blocks would be constructed of my favourite Council pavers. Two 600x600mm and two 600x750mm. The larger ones would give a little over hang on the front of the plinth.
NOTE:– These concrete slabs are known as “Council Pavers” in the UK as they are used by the local authorities to lay their pavements, they are very thick at 50mm and large at 600mmx750m. ~53kg each. Please be careful! Two persons to lift.
- Builders pad (to mix mortar on)
- Builders level
- Large carpenter saw (To cut Celcon Blocks)
- Rubber mallet
- 40 Celcon Blocks 440x215x100mm (2 Spares)
- 5 Bags of 25kg pre-mixed dry morter (just add water)
- 2x 600x600x50mm Council Pavers
- 2x 750x600x50mm Council Pavers
- Water (via a hose-pipe)
1st Layer of blocks
The brilliant thing about using Celcon blocks is that you can cut them effortlessly in half with a cheap carpenters saw. I was quite surprised that within 4 strokes you cut through 215mm of block. I double checked the compressive strength and the blocks are strong but seemed to easy with my new saw.
So each layer of blocks would be 2.5 blocks long. I cut the half blocks and would move the half block to different positions depending on the layers so that you get good brick overlap. Here is the first layer
2nd Layer of Blocks
Much to my amazement if you follow the instructions on the mortar bags (add water to suit) are very accurate. Thankfully if you get it too wet you add a bit more mortar, if it’s too dry keep adding water. One thing that did catch me out is how little water is needed. However, you quickly realise what is good or bad. I found 2/3rds of a bag did a layer of blocks.
So after waiting a day I had a go at layer number two. As I am creating 3 seperate walls I decided that waiting a day for a layer to “go off” was better for structure and my patience. The weight of the blocks does squeeze the mortar, so if you try and do two layers you have to be quite consistant. I was determined to keep my level of the plinth as much as possible.
2nd layer of blocks was laid with the half block shifted relative to the previous layers half block. Remember to be generous with mortar and then tap down with the trowel to get your level.
As you can see I am putting a column of blocks inbetween each pair of walls. The sideways shots look a bit lik an optical illusion but the three wall are not linked in anyway.
NOTE: At all times I checked each wall was level. I did check the leves between walls and this remained equal as each layer was always made from the same mortar mix. Therefore no risk of different mortar thicknesses in a layer
3rd and 4th Layer
The third layer was done in the morning and the 4th layer was done in the afternoon. I decided to push on a bit with the third and fourth layer due to the success of layers one and two. Now it was successful but will admit I did try to lay one layer on top of the next and my level started to go. So I removed the premature 4th level. I’m sure a pro-bricky would have no problems but all my tapping of the fourth layer push out mortar from the 3rd layer…so I started again.
So 3rd layer was relaid and level checked. Then 5 hours later I added the fourth layer and it all seemed much more substantial, straight and (you guessed it) level!
TIP: Use brand new bags of pre-mix mortar (or any cement product) as once you open a bag the cement starts to degrade. Using fresh bags meant I knew that all the strengthening reactions would take place to stick and hold my walls.
Placing the Plinth on the Blocks
I waited another 24 hours to allow the blocks and mortar to dry and develop some strength before lifting the large concrete pavers into position.
I mixed up a large batch of mortar to place on the top of the blocks and layered it entirely over the blocks. I did this so that I would tap the concrete pavers into place. I say tap…but it was pretty aggressive with the rubber mallet if I am honest.
NOTE: Concrete Pavers very heavy, two man lift
Placing the Concrete pavers on the mortar is really quite tricky, you should not attempt this on your own so that you place it down on the mortar Level. Once you you get the first paver level, get the second. I did the rear left corner first and then did the right rear corner. The second stone I levelled to the first stone. The 3rd and 4th stones were levelled and levelled to all the other stones.
I know that I have been really keen on the level of the plinth and this is purely due to knowing that the pizza oven dome will be a structure that supports itself. Therefore having a level base will prevent one side being higher than the other and upsetting the structure.
I wasn’t happy with the front two stones as they dropped too low and therefore I removed them and added additional mortar and replaced the stones. It took some serious smacking of the rubber mallet to achieve the level but I am very please with the finished plinth. (and not having to use concrete)
So I have a plinth, it is 1200 x1450mm and there is space underneath to store wood. Did I mention that it was level 🙂 I also have no fear putting 750kg of pizza oven on it.
Next phase is starting to build the oven…