The Cost of a Roof Overlay plus the Advantages and Disadvantages

One of the main reasons to overlay a roof is that the cost is lower, avoiding the tear down costs and dump fees to dispose of the old roof. It’s also quicker which is another reason why it is cheaper as there are less labor charges.

What are the drawbacks of overlaying a roof?

One of the main drawbacks is that you can overlay the roof once so if you plan to stay in the property for a very long time then once your current roof has reached the end of its natural life, you will have to tear down both roofs and start again – you can’t overlay a third time. So, next time round, you will have double the disposal costs and also near enough double the labor time to remove two roofs rather than one. There is a short-term financial advantage to a roof overlay but it will end up costing you more money in the long run.

Another key factor to take into account is that an overlaid roof won’t last as long as a new roof laid directly onto the top of the house; a double roof will trap extra heat which can warp or prematurely age the overlaid roof on top.

Something else that may stop you in your tracks is that the house has to be structurally strong enough to bear the weight of two roofs so if you are considering that you might need to shore up the foundations and the walls, then any cost saving with a roof overlay will quickly be overtaken.

The opportunity to inspect the base roof decking is lost with a roof overlay so any repairs or making good will be left for potentially another ten to fifteen years and, bear in mind, this is the structure you are just about to add a whole heap more weight to.

Sometimes the finish on an overlaid roof is not as good and neat as your old primary roof may not be perfectly flat and so the roof overlay might not have quite the smooth and level look because it will reflect what lies beneath it which could be sagging and uneven. As well as aesthetics, the overlay may not be as robust as a completely new roof as the shingles are designed to be laid on a perfectly flat surface and may catch in high winds.

In terms of ROI – Return on Investment – an overlaid roof may actually dent the value of your home as it won’t have nearly the financial uplift, cachet and curb appeal of a brand new roof built from scratch.

What do roof codes say about roof overlays?

Roof codes are regulations that cover the construction of a roof on domestic and commercial buildings; they are primarily concerned with safe construction and also want to promote efficient buildings which are watertight and produce the minimum carbon emissions.

Roof codes usually provide quite specific guidance about roof repair or replacement and any new roof covering can not be installed on damaged structural roof components, tricky when you can’t see or access the underlying deck. This is one reason why some roofers won’t undertake roof overlays. Further, the existing roof covering layer must be in good enough condition to support the overlay. Some regional roof codes are very specific and give detailed instructions about when recovering is permitted and when replacement is required so do check your local roof code first to avoid setting out on the wrong path. Some jurisdictions ban roof overlays completely and others will specify that a substantial portion of the roofing materials are removed in order to evaluate decking and roof to wall connections particularly on buildings located in a high wind region or for other special circumstances which the code will document.
Roof codes can vary from state to state so discuss with your roofer whether they think your overlay plans will run into difficulty with your local roofing code.

Finding a professional roofer for an overlay project

Not all roofing contractors will offer a roof overlay service as some believe that this is not the best and most professional way to renew a roof. For a new roof overlay to perform its intended function, the roof underneath needs to be in as near as possible perfect condition in which case why do you need a roof overlay in the first place?

It is a bit counter-intuitive to cover up a perfectly good roof, either it is in poor repair and needs replacing or it isn’t. The main criticism that some roofers have for overlays and why they dislike them is that they cannot inspect the true condition of the existing roof which can only be revealed if all the old roofing material is removed to reveal the deck. Sometimes, a really experienced roofer can still find signs of hidden damage, but it can be a bit of a shot in the dark with a roof overlay particularly if you don’t know the history of the existing roof or how well it has been looked after.

Assessing your roof for an overlay

Take advice and estimates for two or three different roofing contractors, if your roof is in good condition and this is pretty evident or you have documentary evidence to show how old it is and how it has been looked after then you might be able to persuade a reluctant roofer to provide a roof overlay for your home.

The roof must be thoroughly inspected at height both internally and externally for a roofer to establish whether firstly the work is feasible and secondly, whether or not it will infringe the local building code or what the roofer will need to do in order to establish this as the code will specify how this inspection must be undertaken.

The roofing material choice for the overlay must be suitable for the property and its construction; you might have set your heart on designer roof shingles but if they are too heavy for a second layer, then you may well have to choose something else.

Not all roofs are suitable for an overlay irrespective of what the local building code stipulates. Your main roof may be assessed as suitable for an overlay, the building code might give you the green light but there are other factors which you should take into account. If you live in a location where your roof frequently builds up ice dams in the winter, it is possible that these ice dams could form between the two layers of roof causing serious problems in the form of leaks and water damage (Find out about leaky roof repair costs). High winds or a property situated in a high location can be another cross in the box against a roof overlay so, environment and prevailing weather is another important consideration when it comes to debating whether or not to install a roof overlay.

The impact on resale value

Most prospective purchasers are not keen to see a roof overlay as they know it could be difficult to manage maintenance issues and if they need to renew the roof in the future then they will have to tear off both layers, just adding to the cost. The way to get around this is to make sure both roofs are in great condition and regularly and well looked after and you can evidence this in the form of full documentation. If a buyer thinks that they will have a good ten to fifteen years out of the overlay then it might not put them off. On the other hand, if you have put an overlay on a sagging and defective roof then this will show up in time plus insurers will only insure the top layer so some buyers can use a roof overlay as a bargaining chip to get the price down.

The insurance implications of a roof overlay

An insurance company will only insure the top layer of the roof against damage from adverse weather events so if you do experience bad weather and the entire roof is damaged, then the pay out will only be for the top layer, you will have to bear the cost of any damage to the lower layer and the deck yourself.