OUTDOOR WORKTOPS: HOW TO DESIGN AND SUPPORT THEM

There are several assumptions that we hear a lot when it comes to outside kitchens. Before positively tackling the challenges, I thought I ought to dispel some of the myths…

Anyone can build a barbecue

Unless they are bricklayers or in the building trade, most men wouldn’t get involved in brickwork or plasterwork in the home. But move the work into the garden, and suddenly we all feel comfortable getting stuck in. “Oh yes, I’ll knock us up a barbecue in the garden, love!” we go, and before you know it we are knee deep in sand and cement. But bad brickwork looks even worse outside, and brickwork for a barbecue has to bear weight safely and permanently just as much as indoor work. Don’t bodge it!

If a job’s worth doing, it’s worth doing well. 

There isn’t much stone involved!

Something about being outdoors alters people’s sense of scale. Just as that wardrobe you pick up at the boot sale is far too big for Tommy’s bedroom, so your perception of size in kitchens alters when it comes to barbecue worktops. How many times have we heard, “we just need a couple of small pieces” only to find that both are 800mm deep or more, and of decent length too. Indoors that would be two kitchen islands!

Barbecue kitchens are often very large!

It’s going to cost next to nothing!

This goes with the other two: I’ll do it myself and It isn’t much come together with an expectation of cheapness. But do you want the job to look good? Do you want the installation to be safe? Even using bin-end offcuts (if we have anything large enough), stone worktops in a garden setting do come at a real cost. Yes – it may be very affordable, but it will be a long way from a free gift!

You gets what you pays for – and that applies to barbecue worktops and outdoor kitchens too! 

With increasing frequency we are asked to quote for installations involving firepits or pizza ovens, where our stone will be close to or even in contact with naked flames and other intense heat sources. Igneous rocks have been formed under conditions of extreme heat, but may still be susceptible to cracking, flaking or fracture where heat is localised. Commercial granites vary considerably, and there is no source of reliable information on how specific stones behave under the wide variety of conditions that prevail.

A recent customer’s image of a firepit in Steel Grey Granite in Horsham

A recent customer’s image of a pizza oven installation in Dorking. Honed Nero Assoluto worktops to either side of the oven, which does not contain our stone on this occasion.

Affordable Granite is not a firepit or oven specialist, and is not responsible for breakage induced by heat: the customer is responsible for the design of the installation.  As a rule of thumb, we would recommend a 100mm gap between the stone and a naked flame in a fire pit, and slow, steady heating where stone is used in a pizza oven.

Joins

The weak point in worktop layouts is the join. Outdoor worktops expand and contract with temperature. Silicone and resin joins can both be susceptible to breakdown due to re-freezing of trapped water. We would recommend either a) avoiding joins altogether if possible or b) using an outdoor grade silicone with the understanding that occasional refilling of the joint will be needed.

Close up of the join at the corner of an indoor kitchen – Blue Pearl Granite

The Support Structure

The key challenge in outdoor kitchens is support of the worktops. It is worth separating out the two elements: the support structure and the surface on which the stone will sit. Both need care.

Linked to the widespread perception that outdoor worktops should be cheap is the idea that anyone can build a barbecue. Men who would not tackle kitchen fitting indoors think they are brickies in the garden. This often leads to real awkwardness when we arrive to install worktops on the results. Please take note of the following key points:

• The strength of worktop support is critical: remember that with a granite worktop you are putting 90kg per m2 above the ground.  Brickwork must be sound and properly mortared so it cannot rock and collapse.
• Support for the worktops should be at intervals of no more than 600mm.

• Brick plinths need to be adequately designed to provide support that will not allow the worktop to tip or move, irrespective of any adhesive that may hold the stone in place. An 800mm wide worktop poised on a straight run of bricks 103mm wide does not have lateral support. Design boxes and L-shapes which avoid large unsupported overhangs; make sure that any overhang always has at least twice as much stone the other side of the tipping point; discuss with us any planned overhang greater than 300mm.

• Ensure any boxed-in sections of brickwork have airflow to avoid moisture condensing and perhaps freezing beneath the stone.
• Any join between tops must be fully supported under its own length.
• Do not use a mix of materials (such as bricks and steel bars) to support any joins, as their different expansion rates will place stresses on the stone.
• Kits for the brickwork supports and barbecues themselves can be purchased – for instance from Black Knight of Ashford, Kent. If you are not a bricklayer but keen to do this yourself, you could do a lot worse than buy one of their kits.

The Support Surface

We often say that the quality of a kitchen worktop installation is down more to the kitchen fitters than to our guys. The same goes outdoors. Worktops will only be as level and even as the surface they are sitting on.

The best solution for a long-lived design is to make a flat concrete plinth onto which the stone can be bonded without any gaps (in the same way you would lay a ceramic tile).  Such support is essential for any of the man-made materials such as Dekton or the new Caesarstone.

Alternatively, granite worktops can be bedded onto a wet sand and cement layer. This involves coordination between our fitting teams and the bricklayer.

To achieve level support with uniform adhesion, the worktops cannot be placed on edge on the wet mortar/adhesive and then tilted down into position, as we would normally do in a kitchen. With sand and cement or fast-drying tile adhesive this method would push the wet material out from underneath. Instead, worktops must be lowered flat onto the supporting surface. This may involve additional labour – hence higher costs.

Affordable Granite and Your Outdoor Kitchen, Barbecue or Pizza Oven

We do not construct brick plinths and other support structures for barbecues.

We will mix your own sand and cement for bedding onto well-laid brickwork, or bring tile adhesive for sticking to an existing concrete surface that you have prepared. Either way, this service must be explicitly requested and quoted for in advance. Please do not assume that our fitters will be ready to do this unless it has been arranged.

And, yes, the AG team would love to be invited back for a burger and a beer when you christen the barbecue!