GB2299607A - Drainage unit for door sill - Google Patents

Abstract

A drainage unit (2) forms a door sill and has an upper threshold surface (6) in which an elongate slot (20) is defined. The slot (20) communicates via internal drainage channels (32) to drainage outlets (34) formed at a lower level in the front surface of the unit. The unit allows for effective drainage from a level threshold permitting easy disabled access to a building. Dowels (21) are provided for fixing the ends of a three-sided door frame to the shoulders (19).

Description

DRAINAGE UNIT The present invention relates to drainage units and in particular a unit which is intended to be installed below a door in place of the traditional door sill.

Normally a door sill is raised above the level of the external ground surface in order to prevent the entry of water into the building. Water may also enter a building as wind driven rain and to prevent this a water bar is normally fitted in a wooden or metal doorstep sill. This water bar is a vertically upstanding bar extending along the whole width of the door opening. It seats against a rebate formed in the underside of the door when the door is closed. Any water blown underneath the door hits the bar and is drained down the slope of the sill away from the interior of the building.

This prior art design is effective but results in a considerable step at the threshold of the building which creates an obstacle to the entry of the disabled and particularly those who are confined to wheelchairs. It is therefore proposed that new domestic buildings should either have a level threshold or be capable of conversion to a level threshold. This presents a novel technical problem of providing for the drainage of both surface water and wind blown rain from the threshold in order to keep the interior of the building dry.

In order to solve this technical problem the present invention provides a door sill drainage unit having an upper surface drainage unit, which is characterised in that an internal drainage channel is defined by the unit between a drainage inlet formed in the upper surface and opening to the exterior of the unit at a drainage outlet at a lower level, preferably in a surface adapted to be positioned externally of the building.

By permitting water to drain through the body of the unit, a reasonable fall can be provided in the drainage channel resulting in effective drainage even where the upper surface of the door sill is completely level.

Preferably the unit is manufactured from polymer concrete. Such a material is frost resistant, nonabsorbent and extremely durable. The use of such a material overcomes the problems of rising damp and failure due to freeze/thaw action to which normal concrete is susceptible. Reconstituted stone or natural concrete may also be used.

Preferably, the unit is provided with an integral water bar in the form of an upstanding stop rail along the width of the door opening. Such a water bar would normally be a metal insert. The drainage inlet is then preferably constructed as a longitudinal slot extending adjacent to and externally of the rail.

In order that the invention may be well understood, an embodiment thereof will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which Figure 1 shows a perspective view of one embodiment of a door sill drainage unit in accordance with the present invention; and Figure 2 shows a vertical cross section through the unit of Figure 1.

The drainage unit to be described is a one-piece moulded concrete unit 2. For use in domestic house construction the unit will measure approximately 1 metre in length by 300mm wide and 250mm in overall height. It is a block with a base 4 and upper surface 6, two side surfaces and rear and front surfaces.

The base 4 of the door sill drainage unit 2 is adapted to sit on a level surface which may be the upper surface of a course of bricks below the door opening. A unit of suitable height may be mounted directly onto the foundations of the building. An upper surface 6 of the unit is generally horizontal though it may be raked slightly downwardly towards the exterior of the building.

As shown in Figure 1 may be provided with a moulded pattern to improve grip.

The unit 2 has a front external surface 8 which, in the illustrated embodiment is stepped with an intermediate downwardly inclined step surface 10 joining a first upper vertical surface 12 adjacent the upper surface 6, and a second lower vertical surface 14.

The rear of the unit is essentially provided by a vertical surface 16 with a recess 18 along the width of the unit adjacent to the upper surface 6. This recess 18 is designed to allow the internal floor of the building to be dressed up to the upper surface 6 of the unit 2.

This is useful where the floor is either concrete or wooden.

Raised shoulders 19 are formed at either side of the unit 2. A slot like opening 20 forms a drainage inlet along the top of the unit. The slot extends substantially along that part of the surface between the shoulders 19 which is intended to define a door opening in use. The ends of the slot 20 terminate short of the sides of the unit to enable free ends of uprights of a three sided door frame to be bolted or fixed to the shoulders 19. A projecting dowel 21 is shown in the drawing for the purpose, but other recessed or raised fittings to engage with the door frame may be integrally moulded into or secured to the unit during manufacture. Such fittings will also aid in the location of the door frame and facilitate installation.

Shoulder 19 is intended to be raised above the level of the main threshold and to support a free end of a respective door frame upright. By fixing the door frame at a height above the level of the threshold, the wooden parts are kept above the level of the drainage slot 20.

The door frame is therefore kept clear of any water which may pond on the level upper surface 6 of the unit. The shoulders lift the door frame out of the danger area where the wooden parts could be in contact with water.

The shoulders 19 are, however, optional. If the units are to be used side by side to provide larger openings, units with no shoulders or with one shoulder are suitable.

An upstanding rail 22 is mounted so as to extend along the entire width of the slot 20. The rail is a galvanised steel, aluminium or plastics rail which, in the embodiment illustrated in Figure 2, is formed as an upper part of a reverse "h" shaped extrusion 24, which has two downwardly projecting limbs 26,28 joined by a horizontal portion. The outer limb 26 extends along the outer surface of the recess 18 to provide reinforcement. In use, the door will close against the internal surface of the rail 22 and the horizontal portion of the extrusion 24. The outer limb 28 of the extrusion 24 extends downwardly into the slot 20 to reinforce that inner edge of the slot.

An inverted U-shaped extrusion 30 may also be fitted forwardly of the slot 20 to provide further reinforcement to the outer edge of the slot 20. The extrusions 24 and 30 are cast into the unit 2 during manufacture.

Channels 32 are provided to allow internal communication within the unit from the slot 20 to a series of drainage outlet openings 34 in the lower vertical surface 14 at the front of the unit. Various channel constructions may be designed within the interior of the unit. These channels 32 must have a fall so that water entering through the slot 20 will drain down towards the outlets 34. It will also be appreciated that the design of the channels must take into account the need for the unit to retain overall structural integrity and strength.

Where the unit is manufactured from polymer concrete it is not necessary to carry the damp proof course from the brickwork across the unit. The damp proof course layer can therefore be stopped either side of the unit. A slot or groove (not shown) may be provided in the side surfaces of the unit to allow the free edges of the damp proof course membrane to be dressed into the unit.

When the unit is installed in a building of traditional design, ground level will be typically at the level of the inclined step surface 10 at the front of the unit.

The drainage outlets 34 are positioned to discharge into the ground in front of the unit. The typical water flow through the internal channels will be such that effective dispersal of the water can be achieved by providing a small French drain, that is gravel poured into a shallow excavation, in front of the outlets 34.

If the building is designed on initial construction or is to be converted later to have a level threshold, then ground level will be at the same level as the upper surface 6 of the unit so that the upstanding rail 22 is the only obstacle for a disabled person or a wheelchair to negotiate.

In the embodiment illustrated the internal drainage channels 32 drain to the front surface of the unit.

However, the channels could also drain to the base or side surfaces of the unit 2 depending on the requirements of the particular building construction.

The overall height of the unit can be selected to avoid having to mount the unit onto a separate course of bricks. This can lead to a quicker installation in relation to the traditional wooden sill and brick course.

In order to cater for wider entrances, such as for commercial buildings, private nursing homes or the like, a number of units may be placed side by side. To assist location, the side surfaces may be provided with interlocking shapes. Clearly, the unit could also be made longer but using several units which are of a size suitable for handling by one man makes the unit easier to install.

The unit can be offered in different colours and textures to suit the aesthetics of the building design. As well as polymer concrete, units could be manufactured from either mouldable materials including rigid plastics, reconstituted stone or natural concrete.

Claims (8)

1. An elongate drainage unit for use as a door sill comprises an upper surface (6) to define the threshold of the door, and is characterised in that an internal drainage channel (32) is defined by the unit between a drainage inlet !t0) formed in the upper surface (6) and opening to the exterior of the unit at a drainage outlet (34) at a lower level.

2. A unit as claimed in claim 1, wherein the drainage inlet comprises an elongate slot extending substantially along the surface (6) intended to define a door opening.

3. A unit as claimed in claim 1 or 2, wherein the drainage inlet (20) communicates with a plurality of drainage outlets (34) formed along a front external surface (14) of the unit (2).

4. A unit as claimed in any one of the preceding claims, wherein a vertically upstanding rail (22) is provided adjacent the inner edge of the upper threshold surface (6).

5. A unit as claimed in any one of the preceding claims, further comprising means for fixing respective uprights of a door frame to the unit at either side thereof.

6. A unit as claimed in claim 5, characterised in that the fixing means are raised on upstanding shoulders above the level of the upper threshold surface (6).

7. A drainage unit as claimed in any one of the preceding claims, formed of polymer concrete, rigid plastics, natural concrete or reconstituted stone.

8. A drainage unit substantially as herein described with references to Figures 1 and 2 of the accompanying drawings.