Reroofing over an existing shingle roof: Some facts and what you need to know

With the exception of asphalt shingles, no other pitched roofing materials will allow you to perform the repair process directly over the existing roofing material. By using shingles you'll save time and money and you will manage the renovation process easier and faster. By using bitumen shingles for your roof, you'll reduce the impact on the environment.

When your roof starts to fail, but it is in an overall good condition, a reroofing might be the best choice for you. It means that your roof may be at the end of its life, but its underlying structures and wooden deck are in a generally good condition. 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 predispositions for installing a new layer of shingles over the existing one.

Reroofing can also be done when you simply want or need a change on your roof. If you want a different design or color, or you may be completely renovating your home so you want the roof to match your new style. 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 it. The best IKO shingle for this is 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 old roof – of the existing shingles and the underlying structures. This means that there is significantly less labor needed, as well as time spent on the project, and therefore the costs are lower. Your roofer can immediately start with the installation of the new roof, without spending time on shingle removal and disposal.

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

Renovations of old, worn out shingle roofs are mostly simple and inexpensive jobs when using IKO bitumen roof shingles in combination with the best techniques. The material cost is not the main cost; Stripping off the roof shingles, disposal and labor are even more significant costs! 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 the roof shingles.
• Overall appearance 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.
• In general even roof shingles, not completely worn out, can be shingled over.
• Replace missing roof shingles or shingle tabs and nail down accidentally curled roof shingle edges.
• If necessary, replace rotten wood trim or worn out chimney and rake flashings or to add eaves flashing.
• Uniform and straight edge of drip edge help prevent water seepage 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 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 ones have to be installed after the new layer has been applied. Make sure 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. Take into account that some techniques require more roof shingles than others.

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 don’t need a complete roof replacement, 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 advise you on what the best option is for you.