Method of holding down roof sheathing and shingles

A method for securing a roof sheathing and shingles in a retrofitting reinforcement of an existing roof structure, the shingles being laid on the roof sheathing in a partially overlapping pattern, comprises (a) driving a plurality of fasteners down through selected shingles and the roof sheathing in a selected area of the roof structure into at least one of underlying roof frames; and (b) applying a water-resistant coating to the roof structure to seamlessly cover exposed surfaces with exposed ends and sides of all shingles in the selected area.

TECHNICAL FIELD

The present invention relates to a roof structure of buildings, and more particularly to a method of securing the roof sheathing and shingles of existing structures against winds.

BACKGROUND OF THE ART

Studies of building damage caused by high winds, hurricanes and tornadoes indicate that serious damage very commonly occurs as the roof sheathing, panel or deck (roof sheathing will be only used hereinafter) is torn off, allowing rain to ruin the ceiling and interior construction and contents below and often allowing walls to collapse as well. Further, the torn-off roof sheathings and shingles become wind-borne missiles that can damage or destroy anything in their path including the windows of neighbouring structures leaving those buildings prone to greater damage as well.

Roof sheathings can be securely anchored to the underlying frames such as trusses or rafters during construction. Such practice is now generally followed in hurricane and tornado high risk areas of the United States. In most existing houses at risk, however, the roof sheathing is inadequately fastened down, and this is not easily corrected. Further, even if the roof sheathing does hold intact, the shingles themselves can be “pried off” by high winds. Retrofit reinforcement of existing roof sheathing requires costly removal and replacement of the roofing shingles in order to drive fasteners to secure the roof sheathing to the underlying roof frames.

Therefore, there is a need for an improved method for securing a roof sheathing and shingles in a retrofitting reinforcement of an existing roof structure.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is a method for securing a roof sheathing and shingles in a retrofitting reinforcement of an existing roof structure, the shingles being laid on the roof sheathing in a partially overlapping pattern, the method comprising a) driving a plurality of fasteners down through selected shingles and the roof sheathing in a selected area of the roof structure into at least one of underlying roof frames; and b) applying a water-resistant coating to the roof structure to form a continuous membrane over the selected area of the roof structure covering exposed ends and sides seamlessly with exposed to surfaces of all shingles in the selected area, thereby sealing fastener penetrations against water entry while preventing winds from prying off the shingles.

In accordance with another aspect of the present invention, there is a method for retrofitting reinforcement of an existing roof structure, the roof structure including a roof sheathing supported on a plurality of underlying roof frames, and a plurality of shingles laid on the roof sheathing in a partially overlapping pattern, the method comprising a) driving a plurality of fasteners down through selected shingles and through the roof sheathing into selected underlying roof frames, each of the fasteners being driven through at least one layer of overlapping shingles to cause an enlarged portion of a top of the fastener to abut the roof sheathing; and b) applying a water-resistant coating to form a continuous membrane over an entire surface of the roof structure, seamlessly covering the tops of the respective fasteners and top exposed surfaces with exposed ends and sides of all the shingles, thereby sealing fastener penetrations against water entry while preventing winds from prying off the shingles.

Other features and aspects will be further described in the preferred embodiments described hereinafter with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

InFIG. 1, a roof structure generally indicated by numeral10is illustrated which includes a roof sheathing12which is supported on a plurality of trusses or rafters (referring to underlying frames hereinafter)14in an inclined orientation to facilitate rain drainage. A plurality of shingles16including particular shingles16a,16b,16c, such as asphalt roof shingles, are laid on the top surface of the roof sheathing12in rows in an overlapping and offset pattern to allow water to run off without penetrating through the shingles16. In particular, an upper end portion of one shingle16is directly attached to the roof sheathing12and is covered at least by another adjacent shingle16which is also attached at its upper end portion directly to the roof sheathing12at a relatively higher location while partially overlapping the relatively lower shingle16, such as the adjacent shingles16aand16b.

According to the embodiment as illustrated inFIG. 1, shingles16on the roof sheathing12partially overlap in a more dense pattern such that the roof sheathing12is covered substantially by three layers of shingles16, such as illustrated by shingles16a,16b,16c. A low end portion of first shingle16ais directly attached to the sheathing12by adhesive or by nails and is covered immediately above by a middle portion of shingle16bwhich is attached at its upper end portion directly to the roof sheathing12in a similar fashion at a relatively higher location. The overlapping upper end portion of shingle16aand the middle portion of shingle16bare further covered immediately above shingle16bby a low end portion of shingle16cwhich is attached at its upper end portion in a similar fashion directly to the roof sheathing12at a further higher location (not shown). The roof sheathing12is secured to the roof frame14, for example by nails or screws (not shown), prior to installation of roof shingles16during the construction of the roof structure10.

It is desirable to reinforce the roof structure10in hurricane and tornado high risk areas. Winds at high velocities indicated by arrow18have a tendency to lift the lower end portion of shingles16and then tear the shingles off the roof structure10. In certain areas, the high velocity winds18over the top of the roof structure10create a low pressure air zone immediately above the roof structure10, resulting in a pressure differential across the roof sheathing12and thus a lifting force indicated by arrow20, acting on the roof sheathing12. The roof sheathing12with shingles16thereabove, may be torn off when the lifting force20increases to a destructive level. A retrofitting operation to reinforce the attachment of roof sheathing12to the underlying roof frames14, conventionally requires removal of all shingles and then replacement of roof shingles16after the retrofitting reinforcement of the roof structure10is completed.

According to one embodiment of the present invention,FIG. 1also illustrates a method for securing the roof sheathing12and shingles16in a retrofitting reinforcement of the existing roof structure10. A plurality of fasteners, for example screws22(only one is shown inFIG. 1), are driven down through selected singles16and further through the roof sheathing12in a selected area of the roof structure10, into at least one of the underlying roof frames14. The selected area of the roof structure, for example a front side of the roof structure facing the winds18, is prone to damage caused by the high velocity winds18and the resultant uplift force20acting on the roof sheathing12. In such areas, the winds18also have a tendency to pry off the leading ends30of the shingles16.

A durable water-resistant coating24is then applied to the structure10to form a continuous membrane thereby sealing the fastener penetrations against water entry while preventing winds from “prying off” the shingles16. In this embodiment, the durable water-resistant coating24is applied to form the continuous membrane over the selected area of the roof structure, covering exposed ends and sides seamlessly with exposed top surfaces of all shingles16in the selected area, including those shingles in the area without the fasteners22driven therethrough. It may be desirable to extend the selected area to the entire top surface of the roof structure and therefore, the continuous membrane seamlessly covers the entire top surface of the roof structure.

It is understood that the shingles are selected to receive the fasteners to be driven through because those shingles in the selected area are located above one of the underlying roof frames and allow an appropriate point thereon for a fastener to align with said underlying roof frame.

The screws22may be driven into a depth such that the enlarged top of the screw20is forced to penetrate one or more layers of overlapping shingles16, resulting in a plurality of holes26in the shingles16exposing the tops of the respective screws22. In the embodiment shown inFIG. 1, the enlarged top of screw22is driven down to penetrate all three layers of overlapping shingles16and to abut the top surface of the roof sheathing12, which provides a more secure attachment of the roof sheathing12to the underlying roof frames14. The respective holes26may be filled with a caulking material28prior to applying the coating24, if it is desired. A preferred option is to fill the coating24into the respective holes26when applying the coating24over the shingles16, instead of filling the holes26with a caulking material prior to applying the coating24. The additional screws22added during retrofitting of the roof structure10reinforces the attachment of the roof sheathing12to the underlying roof frames14at selected areas. The coating24forms a durable water-resistant membrane over the entire top surface of the roof structure10which advantageously prevents water penetration through passages defined between the added screws22and the surrounding roof structure10including through shingles16, roof sheathing12and the underlying roof frames14and also advantageously forms a barrier which prevents high velocity winds18from “prying” under a leading edge30of the respective shingles16and thus forcing the shingles16to break away from the roof structure10.

Where shingles remain suitably flexible and sound, a useful variation according to another embodiment of the present invention is shown inFIG. 2, in which a lower end portion of shingle16cwhich is laid above and overlaps the middle portion of shingle16band the upper portion of shingle16a, is lifted to an extent which allows a tool such as screw driver (not shown) to be positioned (as indicated by line32) to drive one screw22through shingles16a,16binto the roof sheathing12and into the underlying roof frames14. When the lower end portion of shingle16creturns to its original position as shown by the broken line, the top of the screw22and the resultant holes26as a passage of penetration of the enlarged top of the screw (if any) are well covered by the lower end portion of shingle16c. This step is repeated in the retrofitting work for driving each of the added screws22in the selected area of the roof structure10. After all screws22are fastened to the roof structure10in the manner shown inFIG. 2, a coating (not shown) similar to the coating24inFIG. 1is applied to the top of the roof structure10to form a membrane over the entire surface of the roof structure, covering the exposed surface of all the shingles16.

The retrofitting method for reinforcing the existing roof structure against winds according to the present invention, is applicable to various types of shingles other than the asphalt shingles described above. The roof structure as described above is taken as an example to illustrate the principle of the present invention but does not limit the application of this invention. When shingles other than suitably flexible and sound asphalt shingles may have a brittle condition which may not readily allow a fold-back action as illustrated inFIG. 2, the fasteners may best be installed directly through all layers of shingles as shown inFIG. 1. When shingle installation methods do not allow such a fold-back action of the shingles, the embodiment ofFIG. 1is also suggested.

Screws have been taken as an example of the fasteners to be installed in the roof structure during the retrofitting operation. However, other types of fasteners such as nails, U-shaped fasteners, etc. may be used in the retrofitting operation.

The fasteners may be driven only in areas known to be subject to extreme uplift forces from strong winds from any direction such as along side roof ridges and near eaves and rakes, because existing nailing is usually more than adequate in less-loaded areas which usually comprise the major portion of the roof surfaces. That knowledge-based practice can reduce costs substantially. However, the subsequent coating preferably covers all of the shingled areas because the wind's maximum prying action can occur essentially anywhere. Shingles, most commonly asphalt shingles, are prone to failure as wind pressures pry under their leading edges and laps. The durable and water-resistant coatings which are currently available, such as transparent acrylic coatings, can protect asphalt shingles almost indefinitely if renewed at proper intervals, while allowing the shingle's colour and texture to show through attractively.

When the combination of fastener installation and coating application is applied to the roof of an existing structure, the roof sheathing and shingles become much more resistant to removal or even to significant damage from high velocity winds, therefore protecting the structure as well as neighbouring structures.