Hi James,
The design can be used for ordinary or fire bricks, as you explained, bricks are fired at high temperatures so they should be fine to use, but if you are unsure about the quality of the London bricks you can always line the inside of your barbecue walls with fire bricks which can be purchased at around 1 1/4 inches (30mm) thick and held in place with a heat resistant mortar, don’t forget to add the fire brick plus mortar depth to your internal dimensions when you start your barbecue. You can always experiment by loose laying the London bricks around the coal tray placed on the ground, ignite the coals and see how the bricks react to the heat.
Davesdiytips.

As far as I am aware, bricks from most storage heaters are made from thermal conductive materials to retain heat, whereas fire bricks are used in fire pits / fire places etc and will stand high temperatures from direct heat, i.e. hot coals. The bricks from the storage heater may crack with the direct heat from the coals, so it may be worth experimenting first before relying on them as a base for the coals.
To ensure your retaining wall built from fire bricks is completely heat resistant you could use a heat refractive mortar, there is a company that sells heatproof mortar in 10 kg ready mixed tubs I came across on the internet :- FIREPLACE PRODUCTS LTD ( fireplaceproducts.info ), just click on fireplace products on their homepage to locate it.
All the best Paul and I hope this helps you with your barbecue project.

DavesDIYTips.

In a long term preparation to building my own barbecue, I have several good quality “fire-bricks” salvaged from old night storage heaters and plan to use these as a base for the charcoals, instead of a metal tray. I plan to lay these on a 3ft x 2ft concrete paver at he correct height. Can you foresee any problems with this idea, please?

Seondly I plan to construct a low retaining wall, again out of fire bricks, possibly to support cooking grids, around three sides of the cooking area and wonder if there needs to be a special mortar-mix, as these bricks may well become rather hot.

Thankyou for any help and advice,

Paul

To build a medium size barbecue using a grill tray of approximately 20″ ( 500mm ) square, I would purchase around 170 bricks, this allows approx 12 per course of brick up to 13 courses high and a few spare for mishaps etc. The quantity of brick required really relies on the height and depth of your design, you can purchase bricks individually from a lot of DIY stores so if you ‘run out’ you can always pick up a few more, just check the store has a stock of the bricks you decide to use.
DavesDIYTips.

yours sincerely

Miss.L.Hamon