RESTORATION OF BUILT-UP ROOFING
Restoration is the process by which a roof assembly is renewed, refurbished or reworked in its entirety. It differs somewhat from day to day roof maintenance in that all the components of the roof assembly are addressed---not just a singular item or two such as a loose counterflashing that might be noted in an annual roof inspection.
No matter what age it is, any built up roof assembly is a candidate for restoration, provided that it is basically sound. A basically sound roof is one that does not contain any defects that cannot be permanently corrected.
Restoration includes several related but distinct treatments:
1. Identification of weak or defective elements that require attention. This process may include infra-red scanning of the roof area to determine the extent and location of areas of wet insulation.
2. Replacement of areas of wet insulation and the related roof membrane.
3. Reinforcement of all membrane flashing.
4. Parapet or wall waterproofing as required.
5. Roof drainage correction as required.
6. Repair of all roof membrane defects such as blisters, ridges and splits.
7. Reworking and/or resealing of metal counterflashing.
8. Resaturation of the roof membrane followed by regraveling.
1. Restoration will extend the service life of a built up roof by 15 to 20 years.
2. The restoration process can be repeated, effectively extending the service life of the roof to that of the building as a whole.
3. The cost of restoration is roughly 1/2 the cost of a new roof.
4. Since little, if any, roof membrane is removed during restoration, the risk of roof leaks during the process is virtually nonexistent.
RESATURATION: Resaturation involves the use of a cold applied, liquefied asphalt and refers specifically to the action of preparing the roof surface, spreading the resaturant and regraveling it. It is a preventative maintenance procedure and is one of the items addressed under restoration. However, since it constitutes the major portion of cost in restoration, the need for it requires additional explanation.
CONSTRUCTION: The layers of paper or felt in the BUR are bonded together with mopping's of hot asphalt. Whereas the felts are not waterproof themselves, they do provide the strength of the system while the hot mopping's supply the adhesive and the waterproofing. New felts are referred to as being saturated since they are treated with oils. The usual protection for this 'sandwich' construction is a hot applied floodcoat into which roofing gravel is spread.
WEATHERING: Normal weathering activity begins with thermo-cycling in the roof. Minute cracks of fissures occur in the coating that reach as deep as the top felt. Warm weather results in the remarrying of the flood coat. Age, ultraviolet light and photo-oxidation tend to raise the melting point of the asphalt until remarrying ceases to occur. The fissuring becomes permanent allowing moisture to penetrate the felts. Oils are oxidized and evaporated from the felts and the moisture in the cracks moves laterally, slowly undermining adjacent asphalt flood coating. The result is an effect called alligatoring. The effects of weathering advance, gravel retention is lost, more and more asphalt is exposed to the elements and more felt is exposed. The exposed felts are defenseless and their deterioration is rapid.
REMEDY: The obvious solution is to reverse the weathering aspect by reinstalling the first line of defense - the flood coat and embedded gravel. Because the roof surface now consists of partially embedded gravel, exposed felts and countless visible and invisible fissures in the intact portions of flood coat, the recoating must be done with something other than hot applied asphalt. The later has poor soakage characteristics so that a flooding of this nature would tend to 'entomb' the cracks, dried out felts and dust pockets. Moisture would most assuredly find its way into these havens and rotting of the felts would be the result.
Instead, a cold applied resaturant is used. This material is properly selected, contains penetrating oils that will soak into the cracks, fissures, exposed felts, dust pockets and other potential water havens. As well, sufficient material is left on the surface to accept new graveling and to hold it firmly. Even if thermo cycling was to open fissures in the new coating, the resaturated roof surface will not soak up water. Furthermore, the resaturant will remarry if fissuring does occur as the first line of defense is re-established.
RESATURANT: As its name applies, the material must have a soaking characteristic. Although most resaturants are cold applied, some products require a primer prior to application. This suggests that the desired soakage characteristics makes a resaturant self-priming. It, therefore, makes possible the continual soaking action that is important for reaching all potential water havens in the original roof surface.
Solvent free, asbestos free and odour free resaturants that meet environmental standards are now available.