Good quality composite shingles can weigh 350 to 450 pounds per square 100 square feet of roofing installed.
Roofing layers shingles.
Chances are your roof structure was designed for a dead load of one layer of shingles plus extra for snow and a safety margin.
When it s time to replace your roof there are several factors that might lead your roofing professional to recommend adding shingles on top of your existing layers.
Keeping a solid roofing layer of shingles is an important way to avoid water damage and leaks.
Richards also estimates that the homeowner saves at least 1 000 in costs associated with removing and properly disposing of the existing shingles.
Beveled wood pieces called horsefeathers must be laid along the thick edges of the shakes to make a fairly flat surface.
Here are the pros and cons.
There are some advantages to roofing over existing shingles says dale richards owner of richards roofing in troy michigan.
How many layers of shingles are allowed on a roof.
Roofing layers from the framing to the shingles so we ll start at the bottom of the deck and work our way up through all the roofing layers until we reach the shingles and sunshine above your roof.
That limit pertains to roofs with up to a 4 12 pitch.
Shingles protect sloping rooftops from the effects of rain snow and hail while providing an attractive crown for the house.
Framing includes the roof trusses that sit at the top of your house and support the weight of all the materials used to build your roof.
Doing it properly will keep you without problems for 20 or 40 years.
First of all multiple layers of shingles simply means layering a new asphalt shingle roof on top of the old one rather than stripping the roof completely to expose the sheathing and replacing it with new shingles.
If two layers already exist you ll need to remove the old layers before installing a new layer of shingles.
Benefits of adding multiple shingle layers.
California roofing codes establish a list of rules that all builders and contractors must adhere to in order to ensure safe building practices within the state.
Asphalt shingles can be laid over cedar shakes or shingles however this is a roofing project best left to pros.
Any more than two layers of shingles can be too much for the roof to handle even if the local building codes don t outlaw it.
California roofing laws cover everything from licensure of the roofing company to the types of shingles that must be used to the slope of the roof.
This felt or rubberized asphalt sheet provides an extra layer of protection between your shingles and your roof deck.
Pros to overlaying a shingle roof.
Most building codes allow this but is it a good idea.
It helps reduce blow off by allowing your shingles to lay flatter and more uniformly.
The homeowner will have two layers of shingles protecting the roof and the home is less likely to have ice dams he says.
Before you reshingle a roof read our step by step guide for adding new shingles over old ones.
