An Easy-to-build Indoor Cat Enclosure

Table of Contents

Overview
Basic Design
Materials
Tools
Preparation

Assembly Instructions
Maintenance
Known Issues
Design Variations
Disassembly for Moving

Overview

As a rescue group we occasionally need to segregate cats while they wait for their forever homes. We have designed an indoor enclosure which can be constructed with simple tools and a modest amount of effort using parts which are either available from your local hardware store or online. Very little skill is required; the instructions below are fairly detailed. If you have any questions, please contact us.

Our requirements were straightforward. We wanted an enclosure that:

provides enough room for cats to run and play;
is sturdy enough to contain cats weighing 10-12lbs who might panic and climb the walls (literally);
is heavy enough that the cats cannot escape by getting a paw underneath it;
is light enough for one person to move about to enable vacuuming up litter etc. that gathers under the bottom of the enclosure walls.;
could be disassembled easily for re-location.

6' x 12' version

9' x 9' version

Please note: The enclosure design described here is not suitable for cats to live outdoors because it is neither raccoon-proof nor protected against UV rays, which can cause the PVC pipe, netting, tie-wraps, etc. to get brittle and break.

Basic Design

The enclosure is a box whose sides and top are formed by a 3' grid of 1" PVC pipe segments joined by standard PVC pipe connectors and covered with plastic netting. The box is 6' high. The original design was 6' wide and 12' long with a single door on one side. However, several variations have been built including a 9' x 9' and one with two doors and a removabel divider. Earlier versions also used alternative parts. (See Design Variations below.)

The PVC pipe is secured to the connectors by screws rather than PVC pipe cement to meet the requirement that the structure be easily disassembled and re-located. (One screw at each end of a pipe segment.) The netting is attached to the frame using cable ties.

The door occupies one vertical panel. There are two options for the door hinges:

Aluminum snap-on hinges purchased online
Home-made hinges formed from two pieces of 1¼" PVC pipe joined with PVC pipe cement. (These are used in the enclosure photos here.)

Materials

Parts

The parts are all readily available, but some are more readily available online than in local hardware stores. We have been ordering the PVC connectors from FlexPVC in Texas. They ship promptly. Given the shipping costs, we usually order the more readily available connectors along with the others; it saves a trip to The Home Depot and amortizes the shipping cost of the special parts over all of the connectors. The netting was not available at The Home Depot.

Part	Use	Est. Unit Price	6'x12' Quantity	Source
1" Side-outlet	Top and bottom enclosure corners.	$2.68	8	Lowe's
1" 4-Way	Connect top edges to verticals, corner posts middle to horizontals. Please note: It is possible to construct an enclosure without these 4-way connectors, but it is a little less elegant. See Design Variations below.	$1.50	12	DP's Bargain Basement
1" Cross	Side and top centers.	$2.98	9	Lowe's
1" Tee	Bottom of vertical posts, middle of the door frame and middle of the door.	$1.34	12	Lowe's
1" 90° Elbow	Door corners	$1.00	4	Lowe's
PVC Pipe: 1"x10' Sched. 40	Frame and door.	$4.13	26	Lowe's
PVC Pipe: 1¼"x2' Sched. 40	You need only 2' (1 x 2"; 4 x 5" if you make your own hinges ). You may be able to buy less than 5' at some hardware stores.	$5.16	1	Lowe's
#10 x 3/4" Phillips Sheet Metal Screw	The picture shows a self-drilling screw, but we found them to require more physical effort than drilling a pilot hole separately and using a regular screw. (#10 x 5/8" work as well.)	$5.98/75ct	2	Lowe's
4'x50' Utility netting	We use 4' utility netting and have to stitch together several pieces using cable ties. 7' x 100' deer netting is available on the internet, but it is too thin to support climbing cats!	$33.03	2 rolls	Amazon
Cable Ties	For the best aesthetics, use natural cable ties to attach the netting to the PVC pipe (up to 300 needed) and black cable ties to stitch pieces of netting together (> 600 needed).	$24.92/1000	1	The Home Depot
Snap-on Hinge	For mounting the door	$5.31	2	Circo Direct
Gate Latch	For securing the door.	$5.08	2	Lowe's
2"x¼" Carriage Bolts	Longer bolts than those supplied with the Slide Action Bolt are needed to secure two bolts on either side of the door.	$0.18/2	2	Lowe's
½"x34¾" dowel	To help adjust the pipe & fittings for a 36" center-to-center grid, a length of dowel to use a spacer is a big help. The length required is 36" minus the diameter of 1" PVC pipe, which is 1¼" for an actual length of 34¾". Any piece of wood would do, but the ½" dowel is easy to cut to length and light to handle during assembly. The dowel must be positioned against both pipes, not the fittings.	$1.78	1	Lowe's
PVC Primer & Cement	PVC cement is only only needed if you make your own door hinges from 1 ¼" pipe.	$8.98	1	Lowe's

Please note:

All pipe used in this project is "Schedule 40". This is the pipe with 1/8" thick walls. Lowe's and The Home Depot sell other pipe and occasionally some thin walled pipe can find its way into the stack of Schedule 40 pipe. Make sure each length of pipe you buy is Schedule 40.
All PVC pipe fittings have "slip joints" rather than threaded joints. This means that the pipe simply slides into the connector (with a little encouragement).
The estimated prices do not include shipping or taxes.

PVC Pipe Segment Lengths

For the frame (excluding the door) all pipe segments are 34 3/8". (Technically, if cut precisely 34 1/2", but if cut by hand we allow 1/8" for adjustment.)
The three horizontal bars on the door are 31 3/8" and the four vertical bars are 32¾".
One 2" segment of 1¼" pipe is needed to support the door latch.
If you make your own door hinges rather than buying the aluminum snap-on hinges, the require four 5" lengths of 1¼" PVC pipe.

Cost

The overall cost for one enclosure is under $300.

Tools

Tool	Notes
Tape Measure	Used for measuring the pipe for cutting.
Sharpie Pen	Used to mark the pipe for cutting
PVC Pipe Cutter	You could use a hacksaw to cut the pipe, but the saving in time and sweat is worth the price of a basic tool if you don't already own one.
Rubber Mallet	The mallet is used for encouraging the PVC connectors onto the pipe. A white rubber mallet will not leave black skid marks on the plastic! Note: Use the mallet on the connectors or on the ends of the pipe. Do not use a regular (metal) hammer; it can shatter the PVC connectors.
Level	Used to ensure that the bottom tees are position correctly so that the sides of the enclosure are vertical.
Electric Drill w/clutch, 1/8" and ¼" bits, Philips Screwdriver bit	Used to make pilot holes and drive the screws.
Scissors	Used to trim the utility netting to make even edges on either side.
Cable Tie Gun	Used to draw the cable ties tight and trim off the excess. Note: I got tendonitis after building the very first enclosure because I used pliers to trim off the excess. The repetitive motion caused the problem. No physical problems having switched to the cable tie gun!
Clamps	Used to hold the home-made hinges together as they set and to hold the door in alignment while the hinges are screwed to the frame.
Adjustable Wrench	A small wrench is used for tightening the nuts on the bolts which hold the slide action bolts to the door frame.

Preparation

There are two essential preparatory steps before assembly of the frame can begin and two others which may be carried out before or during the assembly of the frame:

Decide where the door will go and on which side the hinges will be.
Stand where the enclosure is to be constructed, close your eyes and imagine walking towards the door (possibly carrying food/litter/etc.). Imagine reaching for the door and opening it. Note which vertical section of the enclosure will have the door and on which side it will open. Caution: Do not position the door so that the bolt slides into a corner post. The flex in the structure can cause the door to open if you move the enclosure.
If you don't buy the aluminum snap-on hinges, make your hinges before beginning assembly. This is the only other mandatory preparation required before beginning the assembly.
1. Cut four 5" lengths of 1¼ PVC pipe, two for each hinge.
2. If the PVC cement you have requires it, apply PVC primer along one strip on each of two pieces of pipe.
3. On a flat surface, apply PVC cement to two pieces of pipe and press them together in an upright position to ensure one end of the hinge is level. Then lay the hinge down and, for a surer bond, clamp the pieces together.
4. Repeat the priming, cementing, holding and clamping steps for the second hinge.
5. Allow the hinges to set overnight before using them to support a door!
Trim the utility netting.
We have found that the edges of the netting are often not trimmed cleanly during the manufacturing process. So unroll the netting and trim each edge so that it is uniform the length of the roll. Note: This is pretty tedious, so if you have other volunteers available ... This can also be done while the the frame is being erected.
Cut the PVC pipe.
We have found the project less tedious if the pipe is cut "just in time" as each stage of assembly begins. If more than one person can work on the enclosure then is it possible to have one person cutting pipe while the other assembles the frame.

Assembly Instructions

Simple step-by-step assembly instructions are provided below. They look intimidatingly long, but you can probably read through them once and not even refer to them again while you are actually assembling the enclosure. The intent with the detail is to save you time and grief by passing on the subtle pieces of information learned through the construction of a over a dozen of these enclosures in various configurations.

Note: These instructions were written assuming you are making your own door hinges. If you buy the aluminum snap-on hinges, complete the frame & door assembly ignoring references to the hinges.

Frame

As a general strategy, we have found it easier to construct the top of the frame first, set it aside, build the rest of the frame and then lift the top section up and set it on the vertical pipe sections of the rest of the frame. (Note: In our very first design we skipped the interior of the top and found that then netting pulled the sides inwards, so don' skip the top!)

Select four 3-way connectors for the corners, a four-way connector for each vertical pipe in the frame (8 for a 6'x12' design) and a cross connector for each interior pipe connection. Lay the connectors out in position on the floor so that a complete grid will be formed when the pipe is inserted. Be sure to position the vertical sockets upwards; you are building the top section upside down and will put it right-side up when you install it on the rest of the frame later!
Using the PVC Pipe Cutter, cut the PVC pipe segments.
Insert the pipe segments into the connectors to form the complete grid of the top section. Do not try to seat the pipe completely yet (see next step).
Secure each pipe segment in its connectors as follows:
1. Position the ½ dowel template between the two pipes which are perpendicular to the segment to be secured. Ideally, position the dowel against the pipes where they enter the connectors. (Note: The dowel must be positioned against the pipe, not the connector sockect, to achieve the 36" center-to-center measurement.)
2. Using the white rubber mallet, tap on the connectors until the dowel fits snugly between the pipes. Just tight enough that it doesn't drop out of position on its own.
3. Using the electric drill, first make a pilot hole through each of the two connectors into the pipe segment that runs parallel to the dowel. Then use the drill (with the appropriate clutch setting) to insert a #10x¾ screw into each hole. Note: Whenever possible insert the screws where they are least likely to encounter the future inhabitants of the enclosure whole not requiring contortions on your part! This usually means on the top side of the pipe. It is easiest to work inside the enclosure rather than try to assemble it from the outside.
Repeat for all four pipe segments in a given section of the top of the frame.
After all of the pipe segments in the top section have been secured, raise the completed section on its side and lean it against a wall where you can bring it back through the door of the enclosure to install later.
Next select the connectors for the bottom of the frame: four 3-way connectors for the bottom corners and tees for each vertical pipe segment. Lay the parts on the floor to form the bottom perimiter of the enclosure.
Cut the PVC pipe segments for the very bottom of the frame. Note: The bottom of the enclosure is a complete rectangle; we do not omit a segment where the door will be to maintain the strength of the structure.
Assemble the bottom rail for one long side first:
1. Position the tee connectors flat on the floor and position the corner 3-ways so that the vertical socket is pointing in the same direction as the tees. This will ensure all of the vertical sockets are pointing vertically.
2. Insert the pipe segments into the connectors, but do not screw them into place until the rest of the entire frame has been assembled.
Repeat the assembly for the other long bottom rail.
For the bottom rail on the short side, insert pipe segments into each of the three sockets. Then using the spirit level, hold the vertical pipe segment as close to vertical as you can while inserting the corner connector from one of the long sides.
Insert the short bottom rail into the other long bottom rail to complete three sides of the bottom.
Insert three pipe segments into the tee for the other short rail, hold it vertical using the spirit level and insert the bottom rail pipes into the corner connectors to complete the bottom rail.
Insert pipe segments into the remaining open bottom rail sockets.
Use the spirit level to ensure the vertical pipes are straight up.
Depending on where the door is to be positioned, drop one of the hinges onto the vertical pipe which forms the lower section of the door frame.
Lay out the parts for the back middle rail (2 4-ways and 3 crosses) in the same way as for the bottom rail so that the parts are properly aligned. Then fit the assembled rail onto the vertical pipes at the back of the enclosure.
Insert two pipe segments in to the horizontal sockets of a cross connector for the middle rail at each end. Then put the cross onto the middle vertical pipe on the short side of the enclosure and insert the pipes into the waiting 4-ways at the corners. Repeat for the other end of the enclosure.
On the assumption that the door is in one of the long sides, insert two pipe segments into a cross connector and attach a tee connector to the end which will form the door frame. Insert the assembled piece onto the two vertical pipes and into the corner connector.
Similarly for the side of the door frame which has the shorter distance to the corner, insert a pipe segment into a tee and then put the tee onto the vertical pipe in the door frame and the other end into the 4-way corner connector.
The middle rail is now complete.
Insert pipe segments into all of the vertical sockets.
Drop the other hinge onto the vertical pipe above the other hinge.
Maneuver the previously assembled top section into the enclosure then lift it up and deposit it onto the waiting vertical pipes. It is easier to do this with a helper but can be done alone if you are strong enough.
The basic frame is now assembled and can be secured with screws:
1. Pick a square section on the bottom on which to begin.
2. Double-check the vertical pipes are positioned correctly using the spirit level.
3. Insert the template dowel between the vertical pipes at the bottom of the square you are working on. Using the rubber mallet, tap the connectors until the template dowel is held gently in place.
4. Remove the dowel template, drill a pilot hole in the top of the connectors and then insert a screw into each pilot hole to hole the pipe in place.
5. Next secure the two vertical pipe segments and then secure the top segment of the square you are working on.
Repeat for each square in the frame until they have all been positioned correctly and secured with screws.

Door

Click on the picture below to see the door construction more clearly. The assembly instructions are below the picture.

The strategy for the door is to assemble the whole door frame on the (flat) floor first, securing some of the connectors there and then separate the top and bottom so that they can be inserted into the waiting hinges. Then the hinges are attached to the frame:

Lay out four 90° elbow connectors and two tees for the door.
Cut the three horizontal (31 3/8") and four vertical 1" PVC pipe segments (32¼").
Cut a 2" length of 1¼" PVC pipe
Insert one horizontal pipe segment between each pair of 90° elbow connectors.
For the center bar, insert one end of the remaining horizontal bar into one tee connector. Then slip the 2" segment of 1¼" pipe onto the 1" pipe and insert the pipe into the other tee connector.
Insert the four vertical pipe segments between the tee connectors and the elbow connectors to complete the door structure.
Pick up the door and check that it fits properly inside the door frame. Assuming it does, lay it back on the floor.
The dowel template does not help here, so you will need to measure. The distance across the door to the inside edges of the vertical pipes is 31½" and the distance between the horizontal bars is 32¾" Measure these distances at the point each pipe segment enters a connector.
Secure the horizontal bars to their connectors with screws in the familiar way. Also attach the 2" segment of 1¼" pipe flush against the tee where the sliding bolt will go (opposite side to the hinges), using a screw in what will be the vertical plane so it doesn't interfere with the slide bolts. This little pipe segment has the effect of extending the tee connector so there is a "flat" surface on which to mount the slide bolts.
Secure the top horizontal bar to both of its vertical pipe segments.
Secure the bottom bar to the vertical pipe segment opposite the hinge side of the door.
Using the rubber mallet, separate the top section of the door (horizontal bar and two vertical bars all connected) from the center horizontal bar.
Similarly separate the bottom section from the middle horizontal bar.
Now drill the holes for the slide bolts in the middle horizontal bar:
1. The slide bolt moves through two tabs in the metal backing plate, which also has square holes to receive the head of a carriage bolt:
2. Align the slide bolt horizontally so that the tab closest to the edge of the door is centered on the vertical pipe.
3. Align the top row of holes in the slide bolt backing plate with the center of the middle horizontal bar of the door. There is often a seam in the connector which can be used as a guide.
4. Mark the two square holes.
5. Use the tape measure to note how far the center of the two holes are from the outer edge of the door. Then turn the middle bar over and mark the center of the two holes on the opposite side of the bar.
6. Use the drill with a ¼" bit to drill through the connector and/or the pipe on one side. Then turn the bar over again and drill the holes on the other side. (This is easier to be accurate than trying to drill all the way through.
7. Make sure one of the carriage bolts can fit all the way through each of the two holes.
Swing the two hinges on the enclosure frame outside the enclosure 90° from the frame.
Take the bottom bar with its one attached vertical and its other vertical pipe segment. Position the open elbow below the bottom hinge and insert the vertical pipe through the hinge and into the elbow connector. The bottom section of the door now forms a "U".
Mount the middle horizontal bar onto the two vertical pipes of the lower door section with the end with the holes on the opposite side to the hinges.
Insert the top "U" section of the door through the upper hinge and into the tee connectors of the middle horizontal bar.
Re-adjust the fit so that the inside distance between the door's vertical bars is 31½" and 32¾" between the horizontal bars.
Re-confirm that the door will fit inside the door frame and then secure the remaining door pipe ends into their respective connectors with screws.
Next the door hinges are attached to the main enclosure frame:
1. Make sure you have two clamps handy (an extra pair of hands might also help).
2. Left the door into the door frame and raise it by the upper hinge until it can swing freely in and out and the tee connector on the middle bar is aligned with the corresponding tee connector in the main enclosure frame. Clamp the hinge to the frame in this position.
3. Clamp the side of the door opposite the hinges to the door frame to hold the door in place.
4. Rotate the hinges until the door is properly aligned with the side of the enclosure then fix the upper hinge to the frame (not the door!) with two screws in inch or so from the top and bottom of the hinge on the inside of the enclosure.
5. The bottom hinge should be raised a short distance (¼" or ½" above the bottom 90° elbow at the bottom of the door frame and then clamped to the main enclosure frame as was done with the upper hinge.
6. Again, ensure that the door is properly aligned with the enclosure frame wall before attaching the hinge to the enclosure frame with two screws as before.
Once the door is in place, the entire framework for the enclosure is complete!

Netting

The netting is attached to the frame using cable ties. Start at one side of the door frame. Loop the cable ties around the pipe and through the netting every third hole in the netting. Use the cable tie gun to tighten and cut the ties automatically. Change hands periodically as you work on this.

An important objective with the netting is that after it has been installed, it can be removed as a single piece simply by cutting the tie wraps which hold it to the frame. (See Disassembly for Moving below.)

If you have only 4' netting rather than 7' netting, this is easily the most labor intensive part of the assembly process because you have more seams to stitch between netting sections. (All of the earlier enclosures were constructed with 3' netting as you can see from the pictures.)

Ensure that the roll(s) of netting have been properly prepared by triming the edges so that they are even along both edges.
Start by attaching the bottom of the roll of netting to the bottom of the door frame and secure it up the vertical pipe. Then unroll the netting around the enclosure, attaching it every third hole to the bottom of the enclosure and once in the middle of vertical pipe segments (except around the door frame where it needs to be secured every third hole). Look closely at the pictures to see how this is done.
Do not wrap cable ties around the connectors especially on the bottom of the enclosure. There the cable ties fit in a gap between the pipe and the floor created by the connectors. If you wrap cable ties around the bottom connectors, they are dragged and may break when the enclosure is moved.
If you can only get 4' netting, you will require a couple of trips around the enclosure to cover the sides. With 7' netting, one trip around is sufficient. Note: Do not attempt to match the holes in the netting for the perfect appearance. The netting is never perfectly uniform and you will drive yourself crazy. Simply make sure the netting is fairly taut as you wrap each pass around the frame. Overlap netting segments by one hole so that repairs can be made if one piece of netting breaks at the seam.
Complete the frame netting by stitching one (or more) strips over the top of the enclosure. Note: This can be particularly tiring as you are working above your head. Expect your arms to get tired and plan to rest periodically!
Cut a section of the netting to cover the door itself. Again attach the cable dies around the pipe rather than the connectors. (See the door picture above.)

Installing the Slide Bolts

The door is held shut by two slide action bolts, one on the inside and one on the outside of the enclosure so you can secure the door after you enter the enclosure.

Gather together the two slide action bolts, the two 2" carriage bolts (which are longer than those usually supplied with the slide action bolts) and the two nuts which came with the shorter ¼" bolts.
Insert the carriage bolts through the holes in the backing plate of the slide action bolt to go on the outside of the enclosure.
Standing facing the edge of the door, insert the two carriage boltes through the middle pipe and then put the second slide action bolt over them.
It may take some extra squeezing to be able to fit the nut over the bolt which protrudes only a few threads through the backing plate of the inside slide action bolt. Use the adjustable wrench to tighten the nuts. (The alternative is to buy even longer carriage bolts and cut them down so they do no interfere with the slide mechanism.
Once the bolts are attached the door, attach the socket for each slide bolt to the enclosure frame:
1. Close the slide bolt.
2. Align the socket vertically on the tee connector opposite the slide bolt so that the it fits around the closed slide bolt.
3. Mark the two holes on the connector.
4. Drill pilot holes and insert the screws to secure the socket.
Repeat for the other socket for the slide action bolt on the other side of the door.

Maintenance

These enclosures are light enough for one person to move with a firm shove. This exposes any litter etc. that gathers under the bottom rail so it can be vacuumed away.
The PVC pipe, fittings and netting material can be washed with detergent and water and disinfected with the standard 1/32 bleach solution.
The principal mechanical maintenance required for these enclosures is to replace cable ties when they fall off. Over time cable ties seem to become brittle and snap, especially those used to stitch the netting pieces together. (Hint: Leave a supply of cable ties and netting cast-offs with the enclosure to use for maintenance.)
If young kittens are kept in an enclosure, you need to watch for them chewing through the netting. Older cats do not seem to bother chewing on the netting. The netting can be patched by cutting out a rectangle of netting and securing it over the hole with more cable ties. You might need to spray the netting with Bitter Apple or some similar product to deter the kittens from chewing on the netting.

Known Issues

The weight of the slide bolts on the door can cause the door to sag. While it is convenient to have the slide bolts on the door, it should reduce the sag to put the slide bolts on the frame and just the eyes for the bolts on the door. However, we have not yet experimented with this modification. It will be a little less convenient to close the door this way, however, because it will require two hands.
When one person is inside the enclosure, he/she must open the door to admit additional people because the slide bolt on the inside is holding the door closed. We are exploring alternative closing mechanism which are secure against feline Houdinis while enabling easy passage through the door in either direction at any time.

Design Variations

Enclosure Without 4-way Connectors

While most other parts may be available in a local hardware store, the 4-way connector will probably need to be ordered online. We built an earlier version using tee connectors before we found the 4-way connectors. Note the panels without middle horizontal bars. You'll need shorter pipe segments where tees are used to connect the top to the sides and 1¾" segments to fit the adjacent tees together. Click on the pictures below to see them at full size and the design diferences will become clear:

Two Doors with Removable Separator

We don't have pictures of the separator, but we bolted pipe hangers together to attach a middle wall when the enclosure is to be split into two. In this design the two doors are on the ends of the front wall.

Disassembly for Moving

Cut the tie wraps holding the netting to the frame and lift off the netting as a single unit.
For each connector where you want to separate the frame, use a Sharpie (or similar marker) to:
1. Number the connector
2. Label each arm of the connector with a letter ('a', 'b', 'c', 'd').
3. Mark the end of the pipe with the connector number and letter. (e.g., "7-b").
4. Make a couple of alignment marks on the pipe and connector so that the pipe segment can be repositioned and the original hole used to reconnect it with a screw in the enclosure's new location.