CCC Project Manual PORCH ROOFS - Carolina Cross ... Project Manual PORCH ROOFS Project Components & How-To’s 94 - PORCH ROOFS Porch Roofs Carolina Cross Connection Project Manual

CCC Project Manual

PORCH ROOFS

Project Components & How-To’s

94 - PORCH ROOFS

Porch Roofs

Carolina Cross Connection Project Manual

Common Materials

2x4for rafters

2x6 for headers

4x4 for posts

1x4 for purlins or 4x8 OSB for sheathing

Tin Roofing

Tin Roofing Nails/Screws

16d, 8d, Joist hanger nails

Hurricane clips

1/2” x 6” carriage bolts

4x4 post anchors (optional)

Common Measurements

Rafters are 16” on center

24” overhang over house or mobile home with at least 3” clearance

Front header should have at least 6’8” clearance from porch

Purlins are 24” on center

Tin should overhang 1” minimum on all sides

Porch Roof Components

Dimensions

The porch roof should cover the entire porch, with at least a 12” overhang on all sides. The porch roof should overhang the roof of the house/trailer by 24”. There should be a minimum of

3” between the surface of the house roof to the underside of the porch roof. The height of most doors is about 6’8” (measure to make sure). There should be a minimum height of

6’8” (or whatever the door height is) from the surface of the porch to the lowest point of the under-side of the porch roof to provide enough clearance for the door to open without scraping the porch roof.

Porch Roof Specific Tools

Ladder

Tin Snips

1/2” drill bit

Gloves

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Posts

Use treated 4x4 boards for posts. The porch roof must have at least have 4 posts, one at each corner.

The two front posts must be at least 7’2” from the top of the porch to the top of the post.

The two back posts must therefore be GREATER than 7’2” so that the porch roof will have some slope to shed rainwater. Most of the time, 8’6” (top of porch to top of post) is a good length for back posts.

The top of posts should be cut square; don’t worry about try to cut them at an angle.

The most ideal scenario is to build a new porch with long posts that you leave “running wild.” That way, you can also build the porch roof off of the same posts. This is the easiest and most structurally sound method of building/anchoring the porch roof.

Intermediate Posts: If headers span more than 8’, you must install intermediate posts to support them. If rafters span more than 8’, you must install intermediate posts and an additional middle header to support them.

Post Anchors

If you are installing new posts on to top of an old porch, there are a few ways to anchor. One option is to run posts outside of the porch, directly into the ground, into post holes. 20” deep if possible and resting on solid footing (e.g. brick, rocks, gravel). 12” deep minimum! Postholes should be backfilled with water, then sacrete (approximately 40 lbs per hole). If possible, it’s good for posts to be sitting on rocks in the bottom of the hole (just make sure the post is at least 12” beneath the ground). Do not backfill posthole with rocks. It is also a good idea to bolt the porch roof posts to the porch itself (preferably to porch posts or joists). Do not use cap blocks instead of postholes (not sturdy enough)!

Another method is to anchor posts to the porch. Use “4x4 Post Base” brackets with 2” decking screws to anchor posts to porch. If possible, some or all of these screws should penetrate the porch frame, not just the porch decking.

To anchor posts to a concrete or brick porch, use 4x4 Post Base brackets, anchored to the porch with hex head Tapcons (at least 2” long, ¼” diameter), instead of screws. To install Tapcons, you will also need a 3/16” masonry bit, and hex head bit. Drive through concrete or brick, but do not drill through mortar in between bricks (not strong enough).

You can also anchor the posts any existing post/rail systems, using decking screws and carriage bolts.

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Headers

Use treated 2x6 boards for headers. Headers are bolted to posts and serve as

the supports for rafters. Use ½” x 6” galvanized carriage bolts, washers, and nuts. Install so that the thread-side of bolt sits toward the inside of the porch.

Headers must span no more than 8’. If headers span more than 8’, intermedi-ate posts and a beam must be installed to support.

Outside Bands

Outside bands are fastened to posts and complete the “box frame” of the roof. These boards are OPTIONAL. While they are not absolutely essential to support the roof’s load, they can be very helpful to hold posts and headers steady while building.

Use treated 2x6 boards for bands. 16d galvanized nails may be sufficient for attaching, or use ½” x 6” galvanized carriage bolts, washers, and nuts to bolt. Thread-side of bolt towards the inside of the porch.

Rafters

Use treated 2x4 boards for rafters.

Rafters are the supporting framework for a porch roof. They run perpendicular to the house. They rest on top of headers.

Attach 16” on center, at most.

Rafters should never span lengths greater than 12’. If rafters span more than 12’, intermediate posts and a beam must be installed to support.

Rafters should overhang the roof of the house by 24”. Rafters should overhang the front header by 12”.

Attach rafters by toe-nailing them into the headers and/or using “hurricane clips” (aka “rafter ties”).

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Purlins

Use treated 1x4 or 1x6 boards for purlins. Purlins are thin boards running parallel to the house that are attached to the tops of rafters with 8d or

10d galvanized nails. Tin roofing is in turn attached to the tops of purlins. Attach purlins 24” on center, at most. Purlins should overhang the sides of the porch roof frame by 12”.

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Tin Roofing

Tin roofing (not aluminum, which is more costly) comes in 2’ wide panels and in lengths of 8’, 10’, 12’, 14’, etc.

Two kinds of tin roofing can be used: “5v” and “corrugated” (see diagram below). Corrugated is eas-ier to overlap and helps you avoid having to cut tin.

Panels should overlap each other by at least two corrugations. Tin should overhang the purlins 1” at all edges. Attach tin roofing to purlins with 2 ½” tin roofing nails which have a small rubber gasket near the nail

head. This gasket creates a water-tight seal between the nail and the tin roofing, to prevent leaks. Roofing nails should be driven through the tin and purlins. Nails should be driven in the “valleys” of

corrugations, not the “peaks.” Nails should be spaced approximately 12” apart. If you accidentally punch an errant nail hole, fill it with clear silicone so it doesn’t leak. It is ideal to purchase tin panels that are long enough so that ONE panel covers ONE full run of the

roof, and to create building plans accounting for such. Sometimes you may need to use more than one panel for each full run. If so, lay the lowest run of

paneling first then overlap it with the higher runs of paneling (think about how water travels; don’t give water a way to get under the tin). Make sure the “uphill” panel overlaps the “downhill” panel. The downhill panel must always break on a purlin, therefore, you may need to adjust the spacing of purlins to ensure that downhill panels break correctly. The uphill panel should overlap the downhill panel by at least 12”.

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How to Build a Porch Roof: Introduction

The first thing you need when building a porch roof is a porch over which to build it! This guide will as-sume that the a porch already exists. Make sure that the porch safe, sturdy, and capable of supporting the weight of a porch roof. If it is not, the porch must be repaired or replaced before a porch roof can be

built.

The ideal situation is that the porch will already have posts that are “running wild,” that is, that the posts have not been cut off at the level of the porch or handrails, but are rising high enough in the air to also serve as the supports for the porch roof. Ideally, the posts would be used for supporting the porch itself, the handrails, and the porch roof. Many times, however, you will come into a situation where the posts are NOT running wild, in which case, you will begin by installing a new set of posts for the porch roof.

This example will assume that you do not have posts running wild, so you will need to install new posts.

This section will explain how to build a porch roof at a mobile home.

As you are building, remember that no one should ever climb on a porch roof (not built to support the

weight of a person) or the roof of the house (may damage)!

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How to Build a Porch Roof: Cutting the Posts

1. A post must support each corner of the porch roof. (If you have a span of more than 8 feet in any direc-tion, you will also need intermediate posts and beams. These will make the project much more difficult and involved, so consult with a staff person before attempting intermediate posts. For the sake of sim-plicity, this example will assume that no intermediate posts are needed). You can either build posts on top of the existing porch, or running into the ground outside of the porch. Generally speaking, it’s better install posts that will sit on top of the existing porch, as this saves time, labor, materials, and money. It will make the porch roof sturdier and more aesthetically pleasing. Therefore, this example will show you how to build a roof with posts standing upon and anchored to the porch itself. Again, make sure that the

porch is sturdy enough to hold such weight.

2. The ideal standard is that the front two posts are NO LESS THAN 7’2” LONG from the top of the porch to the top of the post. This will help ensure that there is a sufficient threshold, so that people won’t bang their head into the rafters and so that there will be enough clearance for the door to swing open and closed without getting caught in the rafters. To make sure you’ll have enough clearance, open the door and measure from the top of the porch deck to the top of the door. Most of the time, this distance will

be about 6’8”, and if it is, then you’re safe to make front posts 7’2” long.

3. Now for the back two posts. These posts must obviously be LONGER than 7’2” in order to create a roof that will slope away from the house. If possible, you also want these posts to extend above the lowest part of the house roof, so that the porch roof will overhang the roof of the home. The height of the back posts will also determine the slope of the roof. The longer they are, the steeper the porch roof will be. The roof should be steep enough to shed water, heavy snow and ice, and other things off the roof and away from the house. But for aesthetics’ sake, you also want to the slope of the porch roof to be fairly consistent with the slope of house roof. As a general rule of thumb, the back two posts should be at least 8’6” long. Don’t go any shorter, or else the slope of the porch roof will not be steep enough to do its job. Of course, you can make these posts longer than 8’6”, if you have enough materials to do so (steeper roofs mean longer rafters and tin roofing panels). If you decide to be more daring for whatever reason,

the ideal slope of a porch roof is a 2” drop for every 1’ run.

4. For simplicity’s sake, this example will use the standard 7’2” length for front posts, and 8’6” length for back posts. Measure, mark, and cut two 4x4x8’ posts at 7’2” long and label these as the FRONT posts.

Measure, mark, and cut two 4x4x10’ posts at 8’6” long and label these as the BACK posts.

5. It’s a good idea to keep the end of the post that you have just cut to serve as the TOP of the posts when you begin building. You want the ends of the post that are still “factory-edge” to serve as the BOTTOM of

the posts. Therefore, write a “T” at the cut-end, and a “B” at the factory end of each post.

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How to Build a Porch Roof: Building “Goalposts”

1. Now you will create two headers, using 2x6 boards, one attached to the two front posts, and one at-tached to the two back posts. Both headers must be the same length. To determine what their length needs to be, measure the front and back of the porch deck. Ideally, these measurements should be the same, but if they are not, use the SMALLER of these two measurements. For example, let’s say the porch isn’t exactly symmetrical, and that the back side of the porch measures 7’8” and the front side measures 7’6”. You should use 7’6” as the measurement to measure and cut both headers. Once you have deter-

mined the proper measurement, cut two 2x6 boards at this length, and mark these as HEADERS.

2. Now you will make a GOALPOST.

a. Lay the two FRONT POSTS on the ground. Place some blocks underneath them to keep them slightly

elevated off the ground.

b. Lay a HEADER board on top of the two FRONT POSTS, so that it is flush with the top of the posts (the “T” end), and flush with the outside of the posts. Use a framing square to ensure the angle is square.

Adjust as needed. Continue to hold the header and posts in this position.

c. Drive two common 16 penny galvanized nails (the largest nails) in to the location shown.

d. Bore a hole between the two nails with a ½” or 5/8” drill bit. Do not drill the hole directly in the center of the header width; go a little lower as shown (you are going to drill another hole close by

later on).

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e. Take one ½” or 5/8” galvanized carriage bolt and use a hammer to drive it through the hole so the head is on the HEADER side (not the post side). Place the galvanized washer and nut on the thread

side and tighten it flush to the board (or even very slightly indented) with a wrench.

3. Repeat the same process for the two BACK POSTS. When you’re finished, you should have, for lack of a

better word, two GOALPOST structures. Make note keep track of which is the FRONT goalpost and which is

the BACK, so as not to get them confused later on.

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How to Build a Porch Roof: Setting the Goalposts and Completing the Box

1. The next few steps are crucial and can be tricky, and will require several people to assist. With several people holding it securely, take the BACK GOALPOST, and set it up roughly on the porch where it should go. Hold the structure header-side-out (header-side facing away from the house). Make adjustments to where the GOALPOST should be positioned and hold it so. Use to a level to hold the structure plumb. When you are happy with its position, use a pencil to write on the porch, tracing the outline of the base of the post, where it should sit on the porch. Do the same with the other post. Then move the GOALPOST out of

the way for a moment.

2. Attach a 4x4 post base bracket to the porch in line with the outlines you just created. Deck screws are preferable for this purpose, but 16d nails can work too. Try to drive some or all of these fasten-ers into the decking AND the framing of the porch. (If the porch is concrete or masonry, drill pilot holes with a masonry

bit and drive Tapcons.)

3. Move the BACK GOALPOST back into po-sition, so that the posts rest in the brackets. When you are absolutely sure that everything is correct, fasten the brackets to the posts using deck screws

or 16d nails.

4. A helpful tip at this point is to temporar-ily attach a long 2x4, angled such that you create a large triangle with the post and the ground. Use 16d nails, but don’t embed the head of the nail; let it pro-trude slightly so that you can pull it out later. The 2x4 will serve a brace, helping to hold structures steady and plumb as you continue building.

See diagrams below for help. Be careful not to lean on the posts or braces and knock things out of whack.

5. Now set the FRONT GOALPOST roughly where it should go. Again, hold this structure header-side-out (header-side facing away from the house). Make necessary adjustments. Don’t mark or attach anything

yet, but have several people holding the FRONT GOALPOST plumb.

6. This is a good point to check that the “invisible rectangle” made by the four posts is indeed a perfect rec-tangle (i.e. four sides with 90° angles) and not some other odd shape. Here’s how you do it, and please

note that you can do all of the following measurements at porch-level:

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a. First, measure the distance between the left back post and the left front post. Then, meas-ure the distance between the right back post and the right front post. Make any necessary to the FRONT GOALPOST adjustments to get these

distance to match.

b. Now, measure the diagonal distance from the left back post to the right front post (inside cor-ner to inside corner). Likewise, measure the diagonal distance from the right back post to the left front post (inside corner to inside cor-

ner).

c. If these diagonal measurements are equal or within 1” of being the same, then you’re good to go! If the diagonal measurements vary by more than 1”, then move the FRONT GOALPOST to the left or right to compensate, as much as space on the porch allows. Obviously, you may not have a lot of wiggle room, so just get it as close

as you can.

d. Once the FRONT GOALPOST is in its proper position, outline and anchor its posts as you did with the

BACK GOALPOST, using brackets. Hold posts plumb and attach a long 2x4 to help brace temporarily.

7. Now you can attach the two outside bands, the boards which complete a “box frame” of the roof. Re-

member: these boards are OPTIONAL. They are not necessary to bear the load of the roof, but they can help make the structure much less rickety as you build. Hold both structures plumb, and have someone measure the distance from the top-outside of the back post to the top-outside of the front post. Measure,

mark, and cut a 2x6 at this distance. Attach this board as shown with 16d nails and carriage bolt.

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How to Build a Porch Roof: Attaching Rafters

1. Now you will begin attaching the rafters — 2x4 boards which run perpendicular to the house, and rest on top of the two header boards. Rafters should overhang the FRONT HEADER by at least 12”. Ideally, the rafters should also overlap the house roof by at least 24”, with a space of at least 3” from

the surface of the house roof to the bottom of the rafter.

2. Begin by installing a rafter at the left-most side of the roof. Set a 2x4x12’ board on-edge on top of the headers. Adjust it so that it overhangs the home’s roof by 24”. Hold it in posi-tion, and have someone else make a mark on the rafter where it intersects the outermost corner of the header board. Then measure out 12” from this mark on the rafter, and make an-other mark. Take down the rafter, and cut on the second mark you made (you do not have to make an angled cut). Measure this rafter, and MAKE A NOTE of that measurement — you will use this measurement for all other rafters. Set this rafter back in place, in the same position you had it before, lining up the first mark with the corner of the header. When you are satisfied, fasten the rafter to the headers using hurricane clips at

both ends.

3. Now measure, mark, cut, and install a rafter at the far right-hand side of the porch, using the same proce-

dure. You should now have the two outermost rafters attached.

4. Measure, mark, and cut the rest of the rafters to the same length.

5. It’s important to make sure that rafters are installed such that their front edges are in a straight line with one another. Run a piece of string between the fronts of the two outer-most rafters you just installed. Use a temporary nail or screw to anchor the string. Tie it off tightly so the line doesn’t slip. Use this line to sight where each rafter should end. If you have to fudge one way or the other, make sure that the

front ends of the rafters (the ends farthest from the house) are in-line, since they will be the most visible.

6. Now simply install each rafter, ensuring the proper overhang at the front and, as much as possible, the back of the porch roof. Rafters should be 16” on center, and visually parallel to each other. Use two hur-

ricane clips to anchor each rafter to both headers.

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How to Build a Porch Roof: Attaching Purlins

1. Now you will install purlins, which are thin boards (1x4s or 1x3s) that run parallel to house and perpendicular to the rafters. Purlins should overhang the outside rafters by 12”. Begin at the front of the porch roof (bottom-most part of the slope), and measure the distance from the be-tween the outer-most rafters, outside edge to outside edge. Measure this distance on a 1x4 and make a mark (don’t cut yet). Now measure an additional 24” out from this mark and make a second mark (this will account for two overhangs that will be 12” each). Cut along the sec-ond mark. You should now have a purlin board that is cut long enough to provide a 12” overhang on both sides of the

roof.

2. Write a big “T” on this board to designate as the template for all other purlin boards. Use it to mark and cut all

other boards at the same length.

3. Install purlin boards, 24” on center. Make sure you keep a 12” overhang on both sides of the roof and that the boards are visually parallel with each other. Use 8d or 10d nails

to attach purlins, two nails at each rafter.

Install

Rafters

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How to Build a Porch Roof: Attaching Tin

Roofing

1. Now you are ready to install the tin roofing. These are 2’ wide sheets of corrugated tin that come in lengths of 8’, 10’, 12’, 14’, etc. Tin should overhang 1” past purlins at both ends. If possible, plan to use tin roofing such that you do not have to cut any tin (this is a pain!). If you must overlap roofing panels, make sure the “uphill” panel overlaps the “downhill” panel (think about how water travels; don’t give water a way to get under the tin). Al-ways attach the lower run of tin roof first then overlap it with the higher runs of tin. Make sure the lower runs “break” on a purlin. Finish tin should overhang the purlins 1” at all edges. Attach to purlins with 2 1/2” nails that have a rubber gasket. Always nail in the “valleys” of the corrugations in the tin panels, to create a good seal. If you punch an errant nail hole, fill it with clear silicone.

It’s not a bad idea to check all nails after you’re finished, and apply clear silicone as needed.

2. There is still a gap between the porch roof and the house roof that will allow water to drain onto the porch. You can redirect water using guttering or flashing, if need be. Whatever you choose, DO NOT NAIL through the house roof. This is likely to cause major leaks and damage. Use a silicone adhesive only for

any materials you might attach to the house roof.

3. When the porch roof is finished, check the entire porch roof structure for sturdiness. If necessary, you

may add a few small angled 2x4 braces, running diagonally, to help firm up the structure.

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CCC Project Manual PORCH ROOFS - Carolina Cross ... Project Manual PORCH ROOFS Project Components & How-To’s 94 - PORCH ROOFS Porch Roofs Carolina Cross Connection Project Manual