How to Hot Mop & Sand

Hot mopping helps hold roofing felt in place and protects the surface from water damage, mildew and rot. After hot mopping, which refers to applying hot asphalt onto the roof, homeowners often choose to apply sand or light gravel to improve the roof's surface and make it more durable. Hot mopping is a dangerous, messy process best performed by professionals and experienced do-it-yourselfers. A properly applied felt, asphalt and sand roof can last up to 25 years.

Things You'll Need

• 45-degree cant strips
• Nails
• Rosin paper
• Roofing base sheets
• Cutter
• Asphalt kettle
• Plastic asphalt
• Bucket
• Tar mop
• #30 roofing felt
• Builder's sand
• Trowel

Instructions

1. Nail cant strips at inside corners of the roof so that the strips extend 12 inches past the corner. Because roofing felt can't fit inside tight bends, the cant strips are necessary to seal the corners.

2. Cover the roof's surface with rosin paper. Roll out the first strip of felt across the edge of the roof, perpendicular to the roof's eaves. Roll out additional rosin strips so they overlap the previous strip by 2 inches. After the roof is completely covered, trim excess paper with a cutter and roll strips of base sheet over the rosin paper, using the same methods used to roll out the paper.

3. Add plastic asphalt to a kettle heated according to the temperature indicated on the asphalt's packaging. Different types of asphalt have different melting points. Allow the asphalt to melt to a thin, paint-like consistency.

4. Pour the plastic asphalt into a bucket.

5. Apply a thin layer of melted asphalt over the surface of the roof, using a tar mop.

6. Cover the roof's surface with roofing felt. Roll out the first strip of felt across the edge of the roof, perpendicular to the roof's eaves. Roll out subsequent strips of felt so they overlap the previous strip by 2 inches. After the roof is completely covered, trim excess felt from the edges, using a cutter.

7. Apply a second layer of hot asphalt over the felt, using the same techniques. If necessary, reheat the asphalt to a paint-like consistency. Apply a second layer of felt, then another layer of asphalt, then a third layer of felt and a third layer of asphalt.

8. Distribute an even layer of builder's sand over the surface of the roof, on top of the asphalt. Spread out the sand with a trowel to create a smooth surface.

Tips & Warnings

• Mask exterior walls and the ground under the roof to protect them from asphalt.

• Wear protective goggles, work gloves and work clothes while hot mopping to protect your eyes and skin from burns.

• You can apply asphalt roofing over wood, steel, concrete or foam insulation.

References

• This Old House; Hot Mopping; Tom Silva
• JLC; Build-Up Hot Mop Roofing; David Lopez; February 2005