Reroofing over an existing shingle roof: Some need-to-know facts

Except asphalt shingles, no other roof cover for sloped roofs allows you the process of recovering, directly over the existing roof cover.

Using shingles you save time, money and manage easier and faster the renovation process.

If you look a bit further in the future using bitumen shingles for your roof reduce the impact on environment.  

When you look for a roof improvement or your roof starts to fail, but its underlying structures and wooden deck are in a generally good condition, a reroofing might be the best choice for you. It means that your shingles may be losing granules and are worn out due to age or weather, but they are not causing leaks, they are not curling or missing. These are all good conditions for installing a new layer of new shingles over the existing layer.

Reroofing can also be done when you simply want or need a change. If you are completely renovating your home and your roof needs to match the new style, adding a different design or color to your roof can completely mix up the look and feel of your home. Installing a new shingle layer will give your roof depth and even a three-dimensional appearance, as it is slightly raised due to the existing layer of shingles beneath. The best IKO shingles for this are the Cambridge Xtreme 9,5° or Cambridge Xpress.

When it comes to the financial aspect of reroofing, it is undoubtedly less expensive than a complete roof replacement. The main reason for that is that there is no need for a tear off of the existing shingles and the underlying structures. This means that there is significantly less time and labor needed and therefore the costs are lower. Your roofer can immediately start with the installation of the new roof shingles, without spending time on shingle removal and disposal. Without a tear above all you don’t impact on the environment, as this must become a significant concern for all of us!

After their roof inspection, a professional roofer will come to you with his report or a recommendation, explaining why your roof is or isn’t suitable for reroofing. You can ask for a few roof estimates from different contractors just to be sure that you are doing the right thing. That way you can choose the best roofer for yourself. One of the main and most straightforward reasons a roof isn’t suitable for reroofing is curling shingles, as you can only install a new shingles layer if the existing shingle roof is completely flat and level. A second reason can be the presence of existing damage to the wooden structure underneath, such as rot or sagging.

When using IKO bitumen roof shingles in combination with the best techniques, the renovations of a worn out shingle roof becomes a mostly simple and inexpensive job. Before starting off any project, first check out whether the existing roof shingle layer could remain in place or has to be removed. Depending on local building codes at least three layers of roof shingles can be applied before stripping off the roof shingles is necessary. 

• The condition of the existing roof structure must be strong enough to support the additional load of roof shingles.
• The overall appearance of the roof must be flat. If sagging is visible, there might be structural problems needing to be fixed.
• Split and nail flat all buckled, raised tabs and curling roof shingles.
• Nail warped decking material if necessary.
• The fastening anchorage for the nails in the new roof shingle layer must be tested.
• The existing surface has to be reasonably smooth.
• Nail down accidentally curled roof shingle edges.
• Replace rotten wood trim or worn out chimney and rake flashings or add eaves flashing.
• A uniform and straight edge on the drip edge helps prevent water infiltration under the old roof shingle edges.
• Additional ventilation should be added.

Inspect the complete roof construction looking for defects before starting to reroof. The existing shingles roof should be dry before reroofing as trapped moisture can shorten the lifespan of your roof structure. Clear the roof from debris and fungus before application. Ridge and hip covering has to be removed. New hips and ridges have to be installed after the new layer has been applied. Make sure the nails are long enough to assure sufficient anchorage. To nail down new hip and ridge cap shingles even longer nails are needed. Consider exchanging old metal flashing for new ones. All existing roof penetrations should be taken out of the old layer and have to be reinstalled in the new layer.

Note:

Try fitting the new roof shingles into the existing layers prior to deciding whether to use this technique.  The existing exposure (the exposed part of the roof shingles) mainly determines what the new visual part will be.

Reroofing is a great option for those who have a generally good roof which is at the end of its life cycle or a roof that is slowly losing its function. As opposed to a roof replacement, it does not involve tear off, which means that it reduces both time and cost for the project. It is always a good idea to consult with a roofer you trust, who can do an inspection, give you an accurate estimate, and who will advise you on what the best option is for you.