Tag Archives: lean-to

Adding a New Lean-to

Adding a Lean-To Shed on an Existing Pole Barn

Reader SAM in CANNON FALLS writes:

Pole barn garage“Hello I am looking to add a lean-to to the side of my pole building on the eave side. I was looking to use a mono truss at with a 2/12 pitch and 8′ to the bottom of the truss/ ceiling height. Existing pole building has 6×6 posts with an 8′ on center spacing. The lean to is going to be 24′ wide by 10′ deep with 4 posts and a beam at the 8′ mark (so it would have a 2′ overhang. to connect it to the existing building we were planning on installing a ledger on to the 4 6×6 post on the existing building to hang the mono trusses off of. My question is do I need more posts on the existing building side and truss spacing or what would you recommend for my application.”

Your situation is one seemingly quite simple, however is fraught with potential for creating more structural problems than it resolves.

Here are some general considerations when adding a side shed:

Inadequate footings

Most (especially ones not designed by a Registered Professional Engineer) post-frame buildings have inadequate footing under their building columns. Often this is a result of having been built by a “professional” builder who sees cheaping out here resulting in adding profit to their bottom line. Use of dry bags of premix (https://www.hansenpolebuildings.com/2012/11/concrete/) or inadequately sized concrete ‘cookies’ fall into this category. If your intent is to attach to existing building columns, then an engineer should be consulted to verify adequacy of existing footings for weight of present building and planned addition.

Drift/Slide off loads

If the high side of your proposed addition is lower than the main building eave, then snow will slide off onto your new shed roof. This can easily result in loads being imposed on new roof system far beyond the design capacity of roof purlins and trusses. In some instances, snow slide off can be great enough to actually fail steel roofing! https://www.hansenpolebuildings.com/2015/05/monitor/

What if the high side of shed and the low eave of the original building are at the same height? Doesn’t this solve potential snow problems?

Well, in a word, no. Now snow has a greater surface to accumulate on (one half of main roof plus added shed roof). When winds blow across the shed and up the main roof, they now deposit a greater pile of snow upon the leeward side of the roof near the peak. While all trusses are (by Code) supposed to be designed to support unbalanced snow loads, there is no way this extra load could have been anticipated – potentially leading to a failure of your main building trusses.

This particular scenario can also result in leaks, if not properly framed and carefully flashed – https://www.hansenpolebuildings.com/2014/10/pitch-break/

Moving on to your proposal…

For an eight foot span from the main building wall to the new row of columns, ordering prefabricated roof trusses is going to be an expensive proposition. Although I love prefab trusses (I spent two decades in this industry, in a past life), unless you intend to create a flat, level ceiling in this shed, it just isn’t worth it. Dimensional lumber rafters are most likely your best option.

A 2/12 roof slope may not be your best choice. Most steel warranties are void on roof slopes under 3/12. Building Codes require sealant tape to be used between under and over laps with steel roofing (again adding to degree of difficulty).

Ledger boards are rarely adequately attached to resist imposed loads (remember snow).

If it was my own building – I would hire an engineer to verify adequacy of design. Provided footings were (or could be made) adequate, I would remove sidewall steel from the main building, so rafters could be attached directly to existing wall columns. Then reinstall steel using J Channel around where rafters protrude through the wall. I would hope to use a single rafter on each end, and one each side of existing columns. Roof purlins would be placed on edge between rafters – joist hung to interior ones and over top of end rafters if there is an end overhang.

Lots of considerations here and you have only a single opportunity to do it right or wrong. Best of success to you.

Occupancy, a Single-Slope Residence, and Lean-to Addition

This week the Pole Barn Guru take care of reader questions about getting an occupancy permit in Victor ID, the size and scope of building a single-slope with a loft, and the addition of a lean-to to an existing structure.

DEAR POLE BARN GURU: I follow your posts and have seen some who question if a pole building can be built as a home and get an occupancy permit. I have some property in Victor Idaho, Teton County Idaho building department. My question is: Can I build a small (about 1200 square feet) building in Teton County Idaho and get an occupancy permit to live in it? Thanks! AL in SURPRISE

DEAR AL: My first experience with Teton County was nearly 30 years ago – when, as a General Contractor, we built a post frame building for Driggs Plumbing. Fully engineered post frame buildings are 100% Code conforming structures and when designed appropriately for Risk Category II and a R-3 (residential) occupancy they make for excellent homes. I have read through Teton County’s Building Department information online and see no minimum footprint requirements for homes, however you would be best served to give a call to Teton County’s Planning and Zoning Department at 208.354.2593. https://www.hansenpolebuildings.com/2020/01/your-barndominiums-planning-department/

 

DEAR POLE BARN GURU: Hello. We are in the planning stages of designing our home and are thinking of building a 40×60, single slope home with a loft on the tall side. Have you ever designed anything like this? I am having a hard time figuring out what height walls I would need and what pitch roof in order to accommodate a loft. I am thinking that i would like 10’ ceilings and 8’ ceiling for the loft, but worried that being vaulted, I will lose usable room space fast. Please let me know if you can help. Thanks! NATE in BIXBY

DEAR NATE: For sake of discussion, let’s work from a 12′ loft width. Allowing for your requested ceiling heights at low side of loft, and thickness of floor and roof system, a 22′ height is not unrealistic at this point. With a 3/12 roof slope (typically a minimum to prevent voiding roof steel paint warranty) your eave heights would be 25′ down to 15′.

 

DEAR POLE BARN GURU: How to tie a self-supporting lean-to onto my existing pole building? Ham Lake city inspector said my existing pole building footings don’t support the added weight of a lean-to and therefore need posts on the high side of the lean-to. Pole Building is 30×64. Lean-to is 19×64. Ham Lake inspector says you don’t need to tie the buildings together other than the lean-to roof tucked underneath the existing roof. The 9 posts on the high side lean-to will be 1′ away from the existing 9 post on the Pole Building. I want to tie these two posts together. I’m thinking of cutting a hole in the siding and nailing a 2×6 onto each post at the top somewhere. Do you have any suggestions? Thanks. KEITH in HAM LAKE

DEAR KEITH: Your Building Inspector is absolutely correct. I see far too many cases similar to yours where a lean-to is added onto an existing building and due to inadequate footings results in an up-and-down roofline. Not certain why you would want to go through efforts of trying to connect those columns, and any meaningful connection could result in loads being inadvertently transferred between buildings. To me, it sounds like more work and efforts than it could ever be worth. We had this very same situation when we added a 30′ x 96′ lean-to to our 96′ x 96′ warehouse. We did not tie columns together and have never experienced any sort of negative challenges from it.

 

 

Making Everything Fit Under an Attached Lean-To

Reader GEOFF in MILFORD has an often found potential challenge, he writes:

“I am looking to build a 30×40 pole barn and want to also have a covered lean to for my camper that will run the length of the barn. In order to have the lean to tall enough for the camper how tall do I need to make the peak of the barn? I need at least 11 feet of height under the roof truss to make the camper fit. My thought is that I should be able to make the barn tall enough to just extend the roof out at the same pitch to cover the lean to. But at the same time I don’t want to make the barn taller than I need to make it. 

Hope this makes sense 

Thank you”

Mike the Pole Barn Guru responds:

Yours is a frequently seen dilemma – trying to fit tall things under an attached side shed (lean to). Even worse, when a future situation arises and a shed addition is needed and main building walls were just not tall enough to make everything work comfortably and not have a very low slope shed roof.

Rather than having to make your enclosed building portion significantly taller, I would recommend you approach this with an idea of it basically being a 40 foot square building, with one sidewall ‘pulled in’ 10′. If you went with say a 13 foot eave height, you could have 12 feet of interior clear height both inside, as well as under your roof only portion. This will allow for plenty of headroom both inside (where you could have a vehicle lift) and outside for your camper. With a 4:12 roof slope your overall building height would be 19’8″ under this scenario.

Most folks would take a design approach of trying to work this as a side shed. With a 13 foot eave height on the low side of a 10 foot width shed, at the same 4:12 roof slope, your eave height of enclosed portion would need to be 16’6” making overall building height 21’6”!

Ladder Framing, Use of Red Cedar Posts, and Custom Steel Trusses

This Monday the Pole barn Guru answers reader questions about “ladder framing,” aka bookshelf girts, the use of Eastern Red Cedar posts in post frame construction, and if Hansen provides custom steel trusses.

DEAR POLE BARN GURU: I had a question about ladder framing on a finish shop. I was thinking about running my two by sixes horizontally between my poles. So I could insulate them horizontally with 24 inch batt insulation. Then I wouldn’t have to add nailers on the inside for when I finish it. What’s your opinion? Thank you. DAVID

DEAR DAVID: I am a huge advocate of using commercial bookshelf style wall girts for any post frame building where climate control might be anticipated. Bookshelf girts also lend themselves well to best possible application of sheetrock.

For extended reading on this subject please see https://www.hansenpolebuildings.com/2017/08/bookshelf-girts-insulation/.

 

DEAR POLE BARN GURU: Greetings. We are looking at building a 40’x60′ pavilion. We live in Missouri and are overrun with Eastern Red Cedar. We have used them for posts before for porches and the like. I was wondering if a 10-12″ ERC would work as a post for a pole barn with a 10’roof and double truss construction. ROGER in IRONDALE

DEAR ROGER: Untreated Cedar, left exposed to weather in above ground situations probably has an expected lifespan of roughly 10 years (https://www.fs.fed.us/t-d/bridges/documents/tdbp/decayres.pdf). While you may have better results, it is not something I would or could recommend when properly pressure preservative treated columns are readily available and will outlast any of our lifetimes.

 

DEAR POLE BARN GURU: Hi, I’m putting a leanto on my barn, and I need 4 custom steel trusses.  Do you build and deliver custom trusses or only whole building kits?  The trusses would be ~19′ long for a 39’x19′ roof.  I live in Pennsylvania. KEITH in NEWTOWN

DEAR KEITH: Thank you very much for your interest in a new Hansen Pole Building. We do not use steel trusses in any of our buildings, however it is very possible we could provide a similar design solution using prefabricated metal plate connected wood trusses.

 

What Kind of Trusses Are Pictured?

What Kind of Trusses Are Pictured?

This question was posed by Hansen Pole Buildings’ Designer Doug. Photo isn’t of a Hansen Pole Building, probably raising questions in Doug’s mind as it looks rather foreign.

Only actual trusses in photo are in raised center portion of this monitor style building. Interior trusses were probably sold to building owner as being “double trusses”. In actuality this system has only a single truss placed upon each side of columns. These trusses, even though only inches apart, do not load share. They are only as strong as weakest individual truss. Between trusses, sticking up beyond top of top chords are paddle blocks (read about paddle blocks here: https://www.hansenpolebuildings.com/2012/05/paddle-blocks/) to attach roof purlins.

Monitor wings (or side sheds/lean-tos) have rafters placed each side of columns with paddle blocks as well. Second floor (aka loft) extends out into wing areas, although quickly loses functionality as headroom decreases close to eaves.

More headroom could have been garnered throughout entire second floor had trusses and rafters been positioned to allow roof purlins to joist hang into their sides. When placed as “top running” purlins, interior clear height decreases by purlin thickness. Positioning of roof trusses as lowered, below purlins causes builder to have to frame outriggers (or tails) above truss in order to support sidewall overhangs. Each paddle block makes for a purlin stagger and eliminates one’s ability to predrill roof steel panels. This adds to possibilities of roof leaks being created by each stagger point.

Other concerns exist in this photo. Where roof purlins overhang single end truss, attachment has been made with yet another set of paddle blocks. With an assumption overhangs will be enclosed, this allows for outside air to enter in spaces created between purlins. This decreases efficiency of dead attic space airflow from eaves to ridge.

Solid blocking should be placed between end overhanging purlins to provide continuity of a load path from roof diaphragm to ground. As being built, load path has been divided.

Perimeter beams in this photo show to be inset between the columns. My curiosity wonders how they adequately attach? Your guess is as good as mine.

 

What Size Post Spacing?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: Building a 32’x 50′ barn that’s 32′ high. Trying to determine the extension out from the ridge for the widow’s peak/ hay hood. Didn’t know if there’s a correct mathematical equation for this? PHILIP IN NEW KNOXVILLE

DEAR PHILIP: There is some mathematics involved, but it comes from a structural standpoint, rather than aesthetics.

A widow’s peak is an extended pointed overhang placed in the center end of a barn roof. Historically, they were used as a pulley support to raise hay bales into hay lofts. In modern post frame construction, very few widow’s peaks are actually used functionally, other than as shelter to protect a loft door. More often than not, they are strictly for aesthetics.

The width of the widow’s peak is usually 1/3rd to ¼ of the width of the gabled end of the building. The distance extended beyond the building endwall, or other endwall overhang is up to the eyes of the beholder, but is most typically three feet.

Now for the math…..the roof surface of the widow’s peak must be accounted for in the design of the endwall truss, as well as the supporting roof purlins. The truss manufacturer needs to be aware of the dimensions of any overhangs beyond the end of the building. The supporting roof purlins can be capably designed by the RDP (Registered Design Professional – architect or engineer) who has done the building design. The nicest looking widow’s peak at time of construction, can end up being far less than pretty if it sags over time.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: What is your typical post spacing and what is the maximum spacing the poles can be spread out? RICK IN WATERLOO

DEAR RICK: The most efficient post spacing is going to depend upon the wind and snow load conditions at any particular given pole building site. As a general rule, the best “bang for your buck” is most typically spaced every 12 feet, although 10 foot and 14 foot spacings are often a close second.

On fully enclosed buildings, the wall girts normally become the dictate on how far apart columns can be placed – they usually will fail at 16 foot pole spacing (again, depending upon wind loads).

For buildings where one or more sidewalls are partially enclosed, 24 foot spacings between columns can be fairly easily accomplished. On endwalls, with a clearspan truss, it is possible to have posts only at the building corners.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: Does Macomb Township allow pole barn construction for a garage? Do you work in Macomb Township, MI? PETE IN MACOMB

DEAR PETE: Pole barn (more technically “post frame”) construction is a 100% code conforming construction system. I’ve found jurisdictions which have tried to prevent “pole barn” construction within their jurisdictions, and we have successfully won the battle every time. Jurisdictions can legislate what a building looks like, however it would be improper to attempt to limit a conforming structural system.

Should you (or any other reader) find a jurisdiction which has contrary ideas, please let me know – as I will have a friendly (and persuasive) discussion with the jurisdiction’s legal counsel.

Macomb Township does have an unusual requirement for any type of building – “rat walls”. You can read more about them here: https://www.hansenpolebuildings.com/2012/06/rat-wall/

As to where we do work, Hansen Pole Buildings provides complete custom designed pole building kit packages anywhere in the United States – including Macomb Township.

Mike the Pole Barn Guru

DEAR POLE BARN GURU: I want to add a lean-to on my 42 x 48 pole building. Should I attach 2×10’s to the poles and put purlins on top of them as if continuation of the building, or should I put a ledger across the side and build accordingly. Thanks DION IN RUHKAMP

DEAR DION: Your cart may be slightly ahead of your horse. Before looking at the rafters and purlins, it might be a good idea to read: https://www.hansenpolebuildings.com/2015/07/shed/

Back to your original question – I personally prefer to attach the rafters directly to the columns with roof purlins on edge in between the rafters. As to 2×10’s – depending upon the width of the shed and your snow load, it is not likely they are adequate. With more information, I can give you a more definitive answer.

Mike the Pole Barn Guru