Concrete Base

[woolf26]

Hi All,

Planning on getting moving on the oven in time for summer this weekend.

First thing is first with the base.....

Plan:

- Dig 15cm deep hole 120cm x 120cm

- Cut and lay forms + Level

- Lay 5cm of Stone chippings for drainage under the base

- Cut and Lay 10mm mesh on top of 4 bricks to hold suspended

- Mix concrete (unfortunately by hand) with 1 part cement , 2 parts building sand , 3 parts 10mm gravel

- Pour concrete in as few parts as possible and float/level the concrete against the forms

- Tap around the edges to get any air bubbles out of the concrete

This is the first project like this I've done and first time mixing concrete so want to make sure I am doing everything correctly.

I've also read about a 1000-1200 gauge Polyethene sheet needed to stop rising damp, but am unsure if i need this / where it would go? under the stone chippings? under the concrete layer?

Any advice or pointers would be very much appreciated, especially on the polyethene sheet.

Thanks,

Jack

[richied]

Hi Jack, 120 x 120cm for a base is very small; what type of oven are you planing on building? If it's a dome oven, a 56" x 67"/ 140 x 178cm is more like what you'll need.  If your ground is solid, you can lay concrete directly on to the soil. Polythene is used to prevent the soil wicking away the moisture and drying the concrete too quickly. If it's clay soil, there's no real danger of that. However, be sure to put a layer of DPC (damp proof course) under your brickwork to avoid rising damp. 

Another thing....use sharp sand, not building sand for concrete. For £40 or so, you can buy an 800kg bag of ballast (pre mixed sand/ stone) that you mix with cement 4:1. This is much quicker. You can hire a mixer for around £8 per day, delivered. If you're mixing a lot, which you will be, a mixer is a godsend. 

Good luck, Rich