FIELD

The invention relates to dome-shaped constructions including buildings, shelters, covers, observatories, and radar or ground-based satellite aerial protective structures; wherein the constructions are made from replicated items of a limited range of modular parts each moulded from a plastics material.

DEFINITION

The word "dome" refers to a hemispherical constructed shape, located upon a surface so as to enclose a volume.

The invention is applicable to shapes having an oval outline in a vertical plane, or to shapes in which two sides of a hemisphere are separated by a linear portion.

"Module" or "modular" refer to repetitive usage of identical parts.

"Panel" refers to a formed unit comprising a portion of a dome comprised of a plurality of panels each having a curved outer surface, curved in two perpendicular axes (unless a linear dome portion is to be included, in which case a single axis of curvature may be used for panels along the linear portion). In this specification, "spherical" may include variant panels in which the degree of curvature in one axis may be zero, or different from the degree of curvature in a perpendicular axis over the surface of the panel.

"Tier" refers to a set of panels at the same height about a ground surface.

"Course" refers to a series of mostly identical, fitted-together panels. The word is taken from brickwork. When elongated rectangles are joined along a long side with 50% overlap the resulting structure has optimized strength. In this document a course may be horizontal, or vertical.

The art-skilled worker will appreciate that the above definitions can, and should with suitable consideration as to context, apply to the singular and the plural, and also to the tense of verbs, nouns, adjectives and adverbs derived from the above.

BACKGROUND

The Applicant has previously described entire buildings, such as dwellings, made from a single piece of plastics material by a rotational moulding process in a large oven holding a heated mould that is rotated in one axis only, while feeding a flow of a selected type of plastics granule (to set solid or to set as a foam) into the interior of the mould. Such an oven can produce a round building several metres in diameter and several metres off the ground, as a single item.

For example, in WO/2008/133535 the Applicant described " a bell-shaped product capable of conversion into a dwelling is made in this manner inside a metal mould, open at one end and slowly rotating about a horizontal axis in an oven". That was a 2 metre diameter oven. It was then realised that this method of construction could be applied to the creation of unitary parts for buildings made of fused plastics by rotational moulding techniques. In PCT/NZ2009/000201 the Applicant described single-axis rotational moulding using moulds supported by mounts inside the oven at selected axes of rotation.

Igloos are an example of dome-shaped construction, using found materials rather than manufactured modules.

McSweeney US2012/0204496 describes a building panel module used for making a spherical shell in which single modules each having the shape of almost exactly a right triangle and with specified angles as projected onto a spherical surface are used. There are only two shapes (apart from modifications such as for windows); one being a mirror image of the other. Vacuum forming is employed and a pair of hulls are subsequently joined together to create a two-layered module.

PROBLEM

The problem to be solved is to provide an economical process for manufacture of a set of modular panels adapted for use in construction of dome-shaped buildings. There is a need to provide large, economical shelters that are resistant to effects of high winds. For use in warm countries, ventilation is also desirable. It is known that a dome has inherent strength like that of an eggshell because it comprises a shape having surfaces curved in two directions, which have greater stiffness than a flat surface, or a surface curved in one direction only. The problem is to construct a dome with modular panels that can conveniently be made, transported to, and handled individually at a site.

OBJECT

An object of the present application is to economically provide a quickly, simply and easily constructed building based on a hemisphere or dome shape with modular panels that can conveniently be made, transported and handled individually, or at least to provide the public with a useful choice.

SUMMARY OF INVENTION In a first broad aspect, the invention provides a structure or building (100, 300, 700, 900) to be placed upon a foundation, the structure having a shape of a hemispherical dome characterized in that the structure is formed from a plurality of modular panels each comprised of a thermoplastics material and joined together at the edges by joints; each panel having an exterior surface and an interior surface and an at least four-sided shape corresponding to an outline of a rectangle projected on to a spherical surface.

Optionally one or more surfaces are not curved, as for an extended length between two half-domes.

Preferably the panels are made from a fusible thermoplastics material by a one-step, single-axis rotational moulding process inside a selected one of a range of configurations of moulds.

Preferably each panel has a selected one of a range of configurations according to a location of the panel as a member of a tier within the structure.

Preferably the panels are joined together along complementary joints formed into the plastics material during a moulding process; the joints being selected from a range comprising overlapping joints and tongue-and-groove joints; said joints being capable of being joined together by adhesive or physical fastening means.

Optionally at least one panel includes ventilation means capable of admitting air from an internal surface into an interior of the panel and of releasing air through an external surface into the atmosphere.

Preferably the ventilation means passes convectively from a low intake, through the interior of a contiguous vertical series of panels, and is released at a high outlet.

In one option, the range of configurations provides for construction of the structure (100) as non-overlapping tiers of panels.

In an alternative option, the range of configurations provides for construction of the structure (300) as overlapping tiers of panels.

Preferably the structure (300) is constructed as overlapping tiers of panels wherein the longer sides of any one panels overlap panels of adjacent tiers.

In a related aspect, the range of configurations of panels includes panels (306) having a six-sided shape resembling a rectangle having a corner removed, when projected on to a spherical surface. 95 Preferably the dome shape is supported by at least one encircling girdle at a height above the foundation, attached to one or more tiers of panels and comprised of an inextensible strip.

Optionally the dome is secured against wind by use of a plurality of tie-down straps each anchored to a mass at both ends and passing over the dome at or near the apex.

100 Preferably each strap is comprised of a flexible plastics material including polypropylene and includes a tension adjusting means.

Optionally the tie-down straps are passed through the hollow centres of a series or course of panels.

Optionally the dome is modified so as to provide an openable observation slot for a 105 telescope; the building comprising an observatory.

Preferably there are from 24 to 96 panels forming a lower tier of a structure. 48 panels forming each course of a dome; at least for the lower courses.

Optionally, panels include cut-outs capable of receiving insetted frames capable when in use of surrounding windows, doors, ducts, pipes, or observation slots.

110 Preferably the dome is closed off at an apex by a single panel.

Optionally the apex panel provides at least one vent.

In a second broad aspect, the invention provides a structure or building (100, 300, 700, 900) to be placed upon a foundation, the structure or building having a shape of two hemispherical portions each comprising a half of a dome,, separated in a horizontal 115 direction by an intermediate hemi-cylindrical extension forming a hemi-cylinder and

comprised of one or more courses each comprised of panels curved about a single horizontally inclined axis

In a third broad aspect, the invention provides a structure or building as previously described in this section that is raised above the substrate by a palisade of panels curved 120 about a vertical axis.

PREFERRED EMBODIMENT

The description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention.

Throughout this specification unless the text requires otherwise, the word "comprise" and 125 variations such as "comprising" or "comprises" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference. Reference to cited material or information cited in the text should not be understood as a 130 concession that the material or information was part of the common general knowledge or was known in New Zealand or in any other country.

DRAWINGS

Fig 1 : shows an oblique perspective view of a first dome structure illustrating the major panels.

135 Fig 2: shows some disassembled panels of the first dome structure.

Fig 3 : shows an oblique perspective view of a dome structure making use of overlapping tiers, illustrating the major kinds of panels and a strengthening girdle.

Fig 4a: schematically shows a surface of a single panel.

Fig 4b: is a vertical section through a typical panel with overlap joints.

140 Fig 4c: is a horizontal section through a typical panel with overlap joints.

Fig 5: shows a tongue-and-groove joint.

Fig 6: shows detail of a screwed tongue-and-groove joint.

Fig 7: is an oblique perspective view of a horizontally extended dome.

Fig 8: shows a subassembly of panels from Fig 7, each curved in one axis, including 145 course overlaps as per Fig 3.

Fig 9: is an oblique perspective view of a vertically extended dome.

Fig 10: shows detail of the bottom of a base panel supported by a wheel.

Fig 11 : shows a preferred path of air flow by convection within the hollow cores of the panels as seen in a vertical cross-section.

150 Fig 12a: shows a ground tie or strap passing through the hollow cores of the panels as seen in a vertical cross-section (one half shown).

Fig 12b: is a plan schematic showing the placement of four paired ground ties or straps used for securing a dome to a substrate or foundation.

The invention relates to hemispherical constructions including buildings, shelters, 155 observatories, and other protective structures. Each construction is made from many

copies of a limited range of modular parts; in particular from interlockable modular parts formed from a plastics material by a rotational moulding process. EXAMPLE 1

Fig 1 shows an example dome structure 100 comprised of replicated or modular panels.

160 The apex 102 might be 20 or even 40 metres above the base 101. Access into the interior may be provided as shown in the Fig 9 variant through a door 902a, 902b. In this example there are 6 tiers between the base 101 to the apex 102; 103, 104, 105, 106, 107; and it will be noted that because the panels become narrower, each panel of the highest tiers (106 and 107) overlap two panels of the tier below. According to height, there may

165 be 50 to 100 panels in any lower tier, for a maximum panel width of about 1.5 metres.

The invention is based on the Applicant's development of a single-axis rotational moulding oven for making flat or curved shapes within individual moulds. Reference to Figs 1 or 3 show that a limited range of moulds, about nine to eleven shapes, may be used to mass-produce replicas of panels for an entire dome - apart from inserts for windows or

170 doors. Once the mould itself is constructed, shapes having curves in more than one axis are moulded easily. The construction of each mould includes connections to a rotatable shaft upon a selected axis at a particular angle to the interior of the mould so that during moulding within a hot oven, incorporated thermoplastics granules move about, congeal, and provide a formed shape having substantially even-thickness walls for use as a dome

175 wall unit having a hollow centre. Should internal thermal insulation be required, the Applicant has previously described, as in PCT/NZ2009/000201, a method for adding a foaming type of thermoplastics granules through an axial pipe after the skin has been formed from non-foaming granules. Further, moulds will include edge details to create inter-panel joining means, preferably an overlapping joint.

180 The art-skilled reader will understand that other moulding methods may be used; for example vacuum- forming one flat sheet into a part-spherical panel; or separately forming two flat sheets including edge detail, that can later be fused together around the edges to provide a hollow panel comparable in structure with a rotationally moulded panel as detailed in this specification.

185 PANEL

Nine types of panel are typically used for the simple version of Fig 1, in which there are no vertical courses. (The apex is likely made of a metal part; see later). For the more complex version of Fig 3 in which panels overlap along their vertical edges, as is common practice in brickwork, 11 types of panel are typically used, depending on how the apex is 190 made. The example shown in Figs 1 and 3 has 60 columns of panel in the four low tiers.

The largest of the types is 1 metre across, not including joints, and is at most 3 metres in the opposite direction. Since the panels are intended to be hollow, a person can lift and carry one panel and the dome may be built by one or several people by fastening each panel to surrounding panels, like a large igloo. A panel factory may have one oven and a 195 variety of moulds, or as many ovens as there are moulds in order to increase production.

Each panel has four curved edges in a quasi -rectangular outline. For a dome-shaped construction, each inner and each outer surface of the panel comprises part of a spherical surface; each curved surface having a curve in two planes.

In Fig 3, the lowest tier 303 is comprised of alternating short and long panels, so that the 200 long edges are joined to adjoining panels while a corner of any one panel falls along the middle of an edge of an adjoining panel. Since panels 306 of Fig 3 are used in a tier where the number of panels in a tier is halved as compared with the tier below, the panels of that tier have a cutout along a broader and lower, when in use, end. Otherwise, because as the apex is approached, the panel width would otherwise become inconveniently small.

205 An example panel is shown in 400 in Fig 4a and (with greatly exaggerated curvature) in vertical cross-section in Fig 4b and in horizontal cross-section in Fig 4c. The panel has a hollow interior, unless deliberately filled as described below. Fig 4a shows the rebate 402 around two adjacent edges used to form the inwardly placed part of the overlap joint, while 405 indicates the complementary outwardly placed edges. See also Fig 5. Fig 4a

210 also shows optional air circulation apertures, which when in use may admit air from the interior of the dome at 406, and expel air from the outer and upper apertures 407. The flow of air through the hollow interior of the panel tends to cool the panel so that sunlight causes less heating in the interior of the dome. Apertures 406 and 407 may be made by routing a panel after moulding.

215 A preferred convective air-flow arrangement is shown in Fig 11, wherein the thickness of the panels 1101, 1102 is exaggerated in order to show the path of the air. Air is able to pass through each or a series of the joints 1103, 1104 that occur between contiguous panels along a vertical course after the tongue joint edges have been intermittently cut through during manufacture or during construction; retaining strength yet admitting air.

220 Air is admitted at a low intake 1105 and rises to be released at a high outlet 1107, which should include a rain cover. The Applicant has noted that drawing the air over water in a container 1106 makes it cooler, although that may not be effective in humid climates.

With the exception of the lowest edge 101 of panels of the lowest tier 103 which will be fixed on to a foundation, the edges are moulded as joints with a rebated edge as shown in 225 Fig 4a so that each panel can be fitted neatly to adjoining panels and fastened for example by screws 501, 502 (Fig 5) into place in a configuration as shown in Fig 1 or in Fig 3. Overlapping, complementary edges are preferred, orientated so that rainwater tends to be excluded. Assembly does not need great skill, since screw sites (see below) are marked by dimples that are moulded into the panels at appropriate locations along the seams.

230 Materials

Each panel is comprised of an environmentally resistant thermoplastics material for assembly into a building. Assuming rotational moulding is to be used, an example fusible plastics raw material is a granular polyethylene plastics material; for example ICORE E 3840 made by ICO Polymers, Inc of 6355 Farm Bureau Rd, Allentown, PA 18106, USA. It 235 is a Linear Medium Density Polyethylene plastic material.

Each panel is made using a rotational moulding process inside a closed mould, charged with the particulate thermoplastics material, moved about within a heated oven by rotation until the interior of the mould is evenly coated with a fused layer, and then the mould is removed from the oven, cooled, and opened up, as described by the Applicant in

240 PCT/NZ2009/000201. The moulded panel is hollow and has an empty interior. In an

option the interior is filled with a second thermoplastics material that converts into a foam, which provides extra insulation for use in adverse climates. A variation comprises use of relatively translucent or transparent materials, to increase the amount of light reaching the interior. The surfaces may be painted. For example white paint on the interior

245 surface helps with lighting. Actual windows may be included in the structure by making complementary pairs of adjoining panels that incorporate an aperture formed in adjoining edges; into which aperture a conventional window frame may be inserted.

One advantage of making curved profiles by rotational moulding is that during

contraction and cooling an inherent tendency of the thermoplastics material to buckle or 250 bow noticeable in flat panels, is managed by intentionally making a curved panel. The mould shall be designed so that the correct size and shape is reliably assumed after cooling. Alternative moulding processes such as vacuum forming could be considered, but it appears that rotational moulding is optimal for at least the production volumes expected and it automatically creates a two-skinned panel.

255 Variant panels include panels adapted to border insetted frames for surrounding windows or doors - as frames and lintels 903, or ducts and pipes, or observation slots or the like.

APEX- DETAILS The apex 102 may be closed using for example a metal "spider" having radial projections about a central ring or disk. The disk may be a mount for a short mast carrying

260 communications gear such as antennas. A ventilation structure can be placed at the apex, using a larger central aperture than that of Figs 1 at 102 or Fig 3 at 302.

GIRDLES

Structural strength is provided in part by use of panels that have synclastic curved shapes - both curves in the same direction in two perpendicular axes. The moulded thermoplastic

265 plastic panels have considerable strength. Yet the challenge to optimize material usage against resulting strength remains, as does the challenge to maintain strength under adverse conditions including, for example, an internal fire that softens the panels. A dome comprised of weak or soft panels would tend to sink at the apex and bulge outwardly at the sides. Therefore the Applicant will attach one or more girdles each comprised of an

270 inextensible strap, optionally deformed in order to lie upon the plane of the surface of the panels at the tier onto which it is to be applied. Polypropylene or other plastics need no treatment to avoid corrosion when in place, as is known to the art-skilled worker. One girdle may be applied at the base 102 and used as attachment means to a foundation. An upper girdle or steel reinforcing band 307 is preferably attached to the panels of the tier

275 308 near the apex 302, since the tiers closest to the apex are halved in number from tier to tier and are not easily provided with overlapping sides as was done for lower tiers. For example the girdle may be secured by transfixing bolts as soon as the tier has been completed. Placing the reinforcing girdle 307 at the location shown, rather than at the apex itself optimizes strength since loading is instead distributed along the panels, not at

280 narrow tips. Further girdles may be used at intermediate positions. One obstacle to use of simple girdles is the existence of a door (see 902, 902a in Fig 9. Either the girdle is placed above the lintel 903 above the door, or a rigid frame is placed around the door that transfers tension across the door without obstructing the opening.

Panels that form the lowest course preferably have a lowest edge moulded as shown in 285 Fig 6, with an extended outer periphery or lip 601 produced (by moulding) from the outer surface 203. The outer extension covers a foundation, or an internal floor edge, or in the case of the "observatory" version in Fig 10, a wheeled support (that allows the dome to rotate. 603 indicates the position of an example girdle.

JOINTS

290 Each panel is joined to an adjacent panel along its edges as shown in section in Fig 5. One optional joint configuration is an overlapping joint 402, 405. Fig 4a shows the joint position as a continuous border around panel 400 which may be regarded as an enclosed flat rectangular hollow box having an outline as at 401. The preferred tongue-and-groove joint is shown in Fig 5, between two panels 403 with tongue 402 and complementary 295 groove 503 held together with screws 501, 502. The tongue and the groove are

respectively formed along adjoining edges. Preferably self-tapping, corrosion-resistant screws or plastic fasteners are used. Other possible fastening means; optionally employing more than one type at any joint, include:

a) Physical fasteners moulded into the joints, selected from a range including mating 300 lugs and sockets; including "clip-tight" devices moulded into the plastic, even if they serve only as temporary holds during construction,

b) Plastics glues selected from a range including solvent glues, two-part glues such as epoxies, and glues which become active when dried,

c) Localised application of heat, thereby locally melting the panels on to each other, 305 including heat from a heat gun, from an ultrasonic generator, from an included hot wire, or from a reversibly penetrating hot object.

If disassembly and removal is required, selected physical fasteners that are capable of being undone are used.

One way to create a tongue-and-groove joint without the problems of forming a re-entrant 310 part (the groove) within a moulded object is to simply mould a thinner edge along two adjoining sides, leaving the other two sides as plain edges to be modified by making a saw cut through the panel along the dotted lines 404, 405, that opens up the groove of the joint by opening into the hollow centre. The scrap material cut off may be ground up and recycled as thermoplastics granules. Alternatively, a groove having solid borders can be 315 moulded by using a removable shape within the mould that is withdrawn on removal and cooling, when the usual amount of shrinkage helps release the shape that delimited the groove.

Optionally the hollow interior of each tile is stuffed, after becoming opened, with internal insulation selected from a range including a foamed sheet plastics material, animal or 320 vegetable fibre, or rock or glass wool.

TIE-DOWN STRAPS

Buildings or structures capable of withstanding very strong winds are necessary in some markets. The Applicant has devised a system of tie-down straps or ropes to hold down a dome using the weight of its foundation. Fig 12a which is a plan view schematically shows how a series of straps may be disposed over a dome. For example, pairs of straps at 45 degree intervals may be used. The actual number and placement will be dependent on the vertical courses of panels, since the straps are designed to pass right over the dome but in between the inner surface 1101 of the panels and their outer surface 1102, as shown in Fig 12b. Preferably each strap travels near a vertical joint between courses, and crosses tiers of panels at the internally open joints such as are shown here at 1103. That is, the straps are passed over the dome from one edge to the other while traversing the length of the end-joined cavity between the inner and the outer skins of the assembled panels.

Creation of this condition requires placing either the strap or a pull-through during construction. As shown in Fig 12a there typically are a number of straps; for example strap 1201a-1201b. Note that the panel thickness is exaggerated for clarity.

Fig 12b shows half only of a dome in vertical cross-section, upon soil 1205. A way to secure the strap 1201 on to an edge of a concrete floor 1204 using schematic fasteners 1203 or another effective means is shown. Preferably at least one ratchet tie-down is installed on each strap such as the mechanism at 1202, to allow for adjustment. Tension in the strap is directed in substantially in the same plane as that of the lowest edge of the adjacent panel. The half dome not shown in Fig 12b is identical in relation to tie-down straps.

The Applicant prefers to use the type of woven polypropylene straps that are widely used to tie down loads on trucks. Rope is an option. Steel is another option, but corrosion and a different coefficient of thermal expansion to that of the thermoplastic panels are disadvantages. When in use, the weight of the foundation serves as an anchor for the dome in case of strong winds, while absence of eaves and vertical surfaces assists air flow. The load is widely distributed over the dome. Placing the tie-down straps inside the panels is tidy, maintains strap alignment and placement, and protects the strap from ultraviolet degradation over the perhaps 70 years that the dome may remain standing.

EXTENDED DOMES

In one variant as shown in Fig 7, two half-domes are joined together by a horizontally aligned extension 701 comprised of differently shaped panels in order to increase the internal enclosed volume inside the building or structure 700. Fig 8 shows a series of courses 703, 704, 705, 706 and 707 comprised of panels that have a predominant curve in only one axis, not two. Since panels curved in just one axis do not have the same strength, they may have to include more thermoplastics material, or vertically oriented corrugations (for example; not shown) within the panel surfaces. There is no particular limit to the length of the linear extension 701.

360 By convention, a geometrical dome has a symmetrical, spherical shape, in which the surface has the same curvature in any plane. The invention is also applicable to shapes having an oval outline in a vertical plane. A shape, like half of a hen's egg, in which the sides rise steeply at first, while retaining some curvature, and then curve toward an apex may increase an effective floor area.

365 A vertical extension is easily constructed as follows: a dome 900 mounted upon a palisade of straight vertical and (optionally) horizontally curved panels 901 as shown in Fig 9 approximates the shape described in the previous paragraph yet does not require different sets of moulds. The palisades may be of any reasonable length. The may be considered as forming a raised foundation for a dome as previously described in this specification. This

370 is one way to place a dome on a sloping ground surface. Especially for small domes this variant provides more "head room". This drawing includes a pair of doors 902a, 902b under a frame 903. A ring foundation is shown as 904. This variant would also be suitable as a dome for an observatory, for which a sideways openable slot for the telescope is included in the curved portion of the building. Such a slot is made with a stiff frame to

375 overcome the weakness caused by the aperture. For this purpose the dome is required to rotate. For example the panels 901 closest to the foundation may be provided with wheels 1001 that rotate upon a circular metal or concrete ring 904, as shown in Fig 10. The wheels and the track may be located either at ground level or at the transition between the cylindrical base 901 and the dome itself, so that the cylindrical base and the location of

380 the door 902a, b does not change position. An advantage of this invention is that the

modules can be made sufficiently small to be assembled by one individual, and perhaps repeatedly disassembled and transported for re-use in another place.

VARIATIONS

An option is to create a dome from tiers that, unlike the dome of Fig 1, are rotationally 385 displaced about the dome by half a panel width, thereby creating overlap along

horizontally disposed joints.

A dome of given dimensions may be made from a lesser number of tiers; such as by use of a smaller number of larger panels. This optimization may save on assembly time, but mechanical lifting assistance may be required in order to build the dome. iMnternal 390 dimensions of a standard shipping container may limit panel dimensions. Ventilation may be provided by openings at upper tiers, such as by providing hinged windows in tier 308 in Fig 3.

A large building may include internal supports for several internal floors; useful for example if the dome is to be used as a community service centre for a number of smaller 395 shelters or permanent accommodation surrounding it.

Domes according to the invention may be made without any metal parts, by using appropriate fasteners or techniques which may include plastics screws, that might be inserted into holes previously tapped with a thread by a metal tap, heat fusion, or a glue. A non-metallic dome, particularly if the plastics material is selected so as to have properties 400 compatible with radio-frequency energy at a relevant frequency (such as by having a low absorbtion coefficient) may be used to protect a radar antenna or a ground-mounted satellite antenna from wind and other effects. The girdles would be made of plastics, such as polypropylene straps.

RESULTS AND ADVANTAGES

405 This invention provides prefabricated panels for buildings, so that a building can be

carried to a site as individual or aggregated panels or modules as dictated by the transport facilities available, then erected at the site.

Use of a dome as the basic shape means that no provision need be made for corner blocks or roof tiles or flashing for waterproofing purposes, as would be required for a rectangular 410 building.

The building is relatively strong in relation to wind loading. For instance it has no vertical surfaces nor overhanging eaves that may engage with a strong or cyclonic wind. The tie- down straps are well placed for comprehensive holding purposes.

Optionally, panels of the building are temporarily attached, but not fused together 415 permanently, so that the building can be taken down when no longer required, and used again elsewhere.

Applications include housing for disaster relief, or providing a central building to be surrounded by housing, providing shelter to homeless persons, or barns for animals.

420