Why Do People Put River Rocks On Flat Roofs

I have just had a flat roof put in on an extension.

Why do people put river rocks on flat roofs.

To protect the underlying layer of roofing materials as is the case with built up roofs burs. The weight provided by the gravel is used to anchor down the roof materials therefore using far fewer fasteners to hold the materials to the decking. This protects the other layers from damage by hail or storms also people walking on the roof so they do not damage the waterproof layers below. Flat roofing is not actually flat.

It has a very low slope between 1 4 to 1 2 inch per foot so that it drains water. In my last place the flat roof was covered with small stones which was better on. Tar has a low melting point. The extension is directly beneath the back windows so looks un sightly.

Talk to ten roofing contractors and you ll get ten answers on what the gravel is for but this seems to be the consensus. The membrane is. If there is a complete covering of the roof with small rocks gravel then it is the top layer of a built up flat roof. But such a low slope holds snow and water much longer than a steeply pitched roof and therefore needs a very different material to stay watertight.

All three types of flat roofing cost 250 to 350 per square 100 square feet but prices vary according to region and size of the roof. All the suspect areas have a third layer of felt also. Built up roof bur the traditional hot tar and gravel. Gravel is used on flat roofs for two reasons.

They can be partially loose laid and held down with river rock ballast requires roof structure to support the weight or fully adhered to the roof deck. Rocks are placed on commercial flat roofs for many different reasons if the roof is what is called a ballast roof it is not fastened or adhered down throughout the whole roof. Specifically there are two main reasons to use a ballasted roof system. Epdm and neoprene roof seams are fastened by adhesive and pvc roof seams are heat or solvent welded.

On many flat roof low slope commercial buildings it s common to see gravel on top of the roof. It has a layer of undercoat and then a layer of the self adhensive felt on the top. To weigh down or secure the. In a typical tar and gravel roof which by the way is gradually being supplanted by gravelless roof systems you put down a layer of tar paper then tar and finally gravel.

Have you ever wondered why contractors install gravel on flat roofs.