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Joint Block Paving With a Gun

By: Chris Hogan MSc - Updated: 7 Jun 2011 | comments*Discuss
 
Gun Jointing Mortar Blocks Slabs Paving

Pulling out a gun to solve all your jointing worries doesn't sound right, does it? Well, using a gun of that sort isn't going to fix any driveway issues, unless of course you've been done by a Cowboy Contractor!

Great Idea for Larger Paving Slabs

No, the gun we're talking about here is a mastic gun, the sort used in building for pressing silicone sealant around shower trays or mastic into gaps around windows and doors. Mix up a mortar with the correct ingredients and to the right consistency and add it to a reusable cartridge. Slot the cartridge into the mastic gun, place the nozzle in the gap, and draw it along the gap with a firm, even pressure. Bingo, job done.

It does sound like a great idea. While it would obviously be too fiddly for small scale blocks like Cobbles or setts, running round larger paving slabs with a gun ought to be quick and easy. And if you take care and Lay The Mortar Properly in the joints, then there'll be minimal clearing up afterward, certainly nothing like using the slurry method.

Not as Easy as it Looks

The practicalities of keeping mortar workable do tend to make jointing with a gun more difficult than it first seems. Mortar is essentially fine granules suspended in a liquid, so the components need to be kept well mixed or the resulting bead of mortar will not be string enough or keep moisture at bay.

On a commercial building site this will be resolved by having a large cement reservoir and a pump sending the mix along a hose to the operator's mastic gun. Even so, the vibrations of the pump will encourage the granules to separate from the liquid so plasticisers are introduced to prevent this from occurring.

Manual Methods for Domestic Applications

For domestic or small commercial driveways, the investment in the machinery and skilled operators is simply not worth it. The manual method means mixing mortar to the right consistency in a large bucket. You can use a mixer but prepare small batches as the process uses mortar relatively slowly. This means it may go off before you can use it all.

Once a cartridge has been used up you simply refill it and continue. But you also need to strike and point the joints with a trowel, in the same way as you would with hand grouting. You need to get to this quickly, before the mortar has set, and don't be tempted to put the excess back in the mix or it will block the gun.

Team Up for Good Results

Jointing with a gun is a lot easier if you have someone to help out. The second person can do the work required before and after each jointing run; mixing the next batch of concrete then striking and pointing the run that has just been finished.

If care has been taken with the gun application, the pointing will be quick with little waste. One of the major advantages of this method is that the mortar will go a lot further because there is a lot less waste, so it makes sense to take as much care as possible.

Practice Makes Perfect

It's also worth mixing up a batch to practice on. This might seem like a waste but getting a good jointing run requires more skill than hand jointing, so this will save money in the long run.

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