DIY Grout Flagstone Cure for Stone Dust

Causes

• Before you begin the project, find out what is causing your issues. If your stone dust filler is just being blown away, the cause and the solution are relatively simple. But if the grout is turning to dust or the flagstones is eroding, the problem is probably long-term weather conditions. Moisture is seeping into your surface and going through freeze/melt cycles that are breaking up your materials. To prevent this, buy stone and grout sealants to treat the flagstone and its grout.

Preparation

• Begin by removing any damaged grout or all traces of existing material you want to replace. Cracked grout is just more erosion waiting to happen, so you need to break it out with a screwdriver, pliers or another instrument to reach the base layer on which the flagstones are installed. Brush out all the dust and chips remaining. If you have an air compressor -- or don't mind huffing and puffing -- you can blow out the dust, too.

Mortar Mix

• Mix your mortar carefully. Use one part Portland cement materials to three parts sand. Do not use larger aggregates than sand, since grout needs to be fine enough to fill all the cracks between the flagstone pieces. Mix the materials with water in a grout bag until it resembles a paste or putty. The grout bag allows you to squeeze out the grout like icing on a cake. Too much is better than too little, since you can wipe way extra mortar.

Finishing

• Finish using a damp rag to wipe off any mortar on the flagstones before it starts to cure. Use a jointer or a section of metal rod or wire to press the grout firmly into the cracks. Wait 15 minutes and press the mortar lines in again to ensure a proper, watertight bond. Once the grout has dried, applied a layer of sealant to prevent any further problems.