GB2321262A

GB2321262A - Roof underlay lap ventilator

Info

Publication number: GB2321262A
Application number: GB9724995A
Authority: GB
Inventors: David Frederick Martin
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-01-21
Filing date: 1997-11-27
Publication date: 1998-07-22
Also published as: GB9701216D0; GB9724995D0

Abstract

A roof underlay lap ventilator has ridges (1) and cut-out tabs (3) which allow the ventilator to be installed at the top edge of a lower underlay, to space the upper underlay therefrom. The flat body (2) of the ventilator is tapered to facilitate insertion between the layers of the underlay.

Description

ROOF UNDERLAY LAP VENTILATOR This invention relates to a roof underlay lap ventilator.

It is well known that pitched roofs with insulation below a roof void need ventilating in order to limit condensation by vapour dissipation into the atmosphere, this is conventionally done by many products fixed at the eaves, over, under or even in the face of fascias, at the ridge by special ventilating tiles or wall air bricks all of which are bulky, expensive to produce and fix and alter the external appearance. Further systems involve ventilation through the underlay by forming a hole with an upstand or forming a ventilating space at the felt lap , the former is expensive with limitations in use and cuts the underlay the latter is bulky, relatively expensive and both require fixing by adhesive or nailing . All ventilators require skill to fit, major disturbance of any existing structure, external access problems and a certain amount of building knowledge and experience.

According to the present invention there is provided a roof underlay lap ventilator comprising a thin flat semi-flexible body with raised profiles of relatively small dimensions in cross section and an integral means to grip the top edge of the lower underlay lap. Such means may be a slot or slots so positioned towards one end of the body to facilitate easily pushing the roof underlay lap ventilator down over the top edge of the lower roof underlay between rafters ( at horizontal underlay lap points ) and permit insertion of the top edge of the lower underlay into the slot. When filly instaled the vertical distance between the top of the raised profiles and the top surface of the flat semi-flexible body of the roof underlay lap ventilator creates a ventilation gap between the upper and lower layer of underlay permitting air movement directly from the roof void below through the consequent ventilation gap and up into the void between the top of the underlay and the underside of the roof finish. Further ventilation opportunity is created by any consequent ventilation gap caused beyond the width of the roof underlay lap ventilator between the upper and lower underlay layers at their point of lap.

The length of the roof underlay lap ventilator will at least approximate to common measurements between the top edge of the lower underlay and the bottom edge of the top underlay at the position of horizontal overlaps plus an allowance for material continuity beyond the closed end of any slot or slots serving as a means for integrally gripping the top of the lowef inserted underlay.

The width of the roof underlay lap ventilator will be less than the common measurements between rafters.

The depth of the roof underlay lap ventilator will be determined by the need to permit effective drainage over the underlay layers at the point of laps after insertion of the roof underlay lap ventilator between them.

Such depth is expected to be less than the common roof tile batten thicknesses.

The desired effect is to easily and durably space apart the roof underlay at points of horizontal laps between rafters of new or existing roofs to enable (by making careful optional position choices of underlay lap ventilator) the optimum for ventilation of the roof void below to prevent excessive condensation without causing excessive wind upliiit action on roof tiles, seriously affecting roof drainage over the underlay nor stress damage to the underlay and at the same time maintain a sufficient barrier to moisture (rain, snow and condensation) penetration from above the underlay.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which : Figure 1 shows in plan view the roof underlay lap ventilator Figure 2 shows in perspective the roof underlay lap ventilator Figure 3 shows in cross section the roof underlay lap ventilator Figure 4 shows in longitudinal section the roof underlay lap ventilator Figure 5 shows in section, installed in a roof, the roof underlay lap ventilator Figure 6 shows a pitched roof with some circled position options for the roof underlay lap ventilator Referring to the drawing the roof underlay lap ventilator comprises a thin flat semi-flexible body2 with raised profilesl and an integral means3 (slots) for gripping the top edge of the lower underlay.

In the example shown the raised profiles are so dispersed across the width of the body2 and of variable length so as to leave a margin of flat body2 around the perimeter. At the narrower leading edge of the roof underlay lap ventilator the shape readily permits location and insertion of the body2 between the upper and lower underlays at chosen positions between rafters at horizontal underlay laps. The insertion is caused by hand pressure downward in the direction of roof slope and to the wider edge of the roof underlay lap ventilator about the area of the slots3. Wlth the raised profiles uppermost a consequent ventilation gap is created between the underside ofthe upper underlay and the top ofthe body2.

The roof underlay lap ventilator is fully installed when the integral means3 (slots) have the top edge of the lower underlay engaging the closed end of the slots3.

By applying slight finger pressure downward onto the top of the slots3 just prior to the top edge of the lower underlay making contact with the slots3 the open end of the slots3 is widened to easily facilitate insertion of the lower underlay up into the slot until it engages the closed end of the slots3.

The slots will have a material memory to recover their shape causing an upward pressure onto the underlay whereas the adjacent parts of the body2 resist that pressure causing the integral means3 (slots) to grip the top edge of the lower underlay.

Claims

1. A roof underlay lap ventilator comprising a thin flat semi-flexible body with raised profiles of relatively small dimensions in cross section and an integral means for gripping the top edge of the lower underlay.

2. A roof underlay lap ventilator as claimed in claim 1 wherein the raised profiles may be higher at one end of their length or with or higher towards the middle profiles taken across the width of the ventilator

3. A roof underlay lap ventilator as claimed in claims 1, and 2 wherein the integral means for gripping the underlay may be a slot or slots positioned towards one end and having a shape memory to cause a grip and/or have an adhesive or otherwise shaped or toothed feature gripping part or parts.

4. A roof underlay lap ventilator as claimed in claims 1, 2 and 3 which has a shape on plan that is tapered for ease of insertion between underlays and for handling and storage.

5. A roof underlay lap ventilator as claimed in claims 1, 2, 3 and 4 wherein the raised profiles do not extend for the full width and length of the roof underlay lap ventilator, there being a margin of flat body to the perimeter.

6. A roof underlay lap ventilator as claimed in claims 1, 2, 3, 4 and 5 which has a length approximating to that of the underlay lap length plus an allowance for material continuity for any slots

7. A roof underlay lap ventilator as claimed in claims 1, 2, 3, 4, 5, and 6 wherein the integral means for gripping the underlay (slots) is capable of finger pressure distortion to cause the open end of the slots to be widened to readily accept the top edge of the lower underlay causing grip when the pressure is released.

8. A roof underlay lap ventilator as claimed in claims 1, 2, 3, 4, 5, 6 and 7 wherein the width will be less than the common measurements for rafter spacings.

9. A roofunderlay lap ventilator as claimed in claims 1, 2, 3, 4, 5, 6, 7 and 8 wherein the depth is expected to be less than a common tile batten but determined by the need to limit ingress of moisture from rain and snow and excessive wind uplift whilst permitting drainage over the surface of the underlay and provide optimum ventilation of vapour to outside air via coincidental gaps around roof finishes or through roof finish ventilators.

10. A roof underlay lap ventilator as claimed in claims 1, 2, 3 4 5 6 7 8 and 9 wherein the flat part of the body at the top end may be sloped upward together with the means of integral grip

11. A roof underlay lap ventilator as claimed in claims 1,2,345 4, 5, 6, 7, 8, 9 and 10 wherein the flat body, integral means for gripping and raised profiles are designed to facilitate fitting one roof underlay lap ventilator into another in order to maimise numbers within any given volume.

12. A roof underlay lap ventilator as claimed in claims 1, 2, 3, 4, 5, 6,7, 8, 9, 10 and 11 wherein the position of the roof underlay lap ventilator is designed to take best advantage of the natural occurance of convection currents within the roof void, with or without high or low level ventilation and to dissipate vapour through the coincidental gaps to tiles, slates and other roof finishes to outside air.

13. A roof underlay lap ventilator as claimed in claims 1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11 and 12 wherein the whole body is of such dimensions as to facilitate easy single handed installation.

14. A roof underlay lap ventilator as claimed in claims 1, 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12 and 13 wherein the. body has integral or attached directional installation instructions

15. A roof underlay lap ventilator substantially as described herein with reference to figures 1 - 6 of the accompanying drawing.