Reuben's Home Inspection Blog

Deck Guardrail Inspections

May 15th, 2012 | 7 comments

The CPSC estimates that between 2003 and 2007, there have been over eleven thousand injuries caused by structural failure or collapse of guardrails at outdoor decks.  It’s not tough to understand why – when people have parties in the summer, everyone hangs out on the deck.  Throw in a keg of Busch Light, a few (ahem) ‘people’ that make the rockin’ world go ’round, and a weak guardrail… boom.  Guardrail collapse.  Weak guardrails are one of the most common safety issues with decks.

The current requirement for new deck guardrails is that they withstand 200 lbs of pressure at any point along the top rail (Table R301.5).  Actually, this standard applies to all guardrails, both inside and outside the house, but decks are the place where it matters most.

My standard method for testing guardrails has always been to just push on them a little.  If they feel weak, I recommend having them reinforced or rebuilt.  Once a guardrail moves an inch or two without much pressure, I stop pushing; I don’t want to be the one to break it.  Home inspections are supposed to be visual, I know, I know… but I like to touch stuff.

I’ve never used any type of testing equipment, but I recently picked up a fancy-schmancy piece of highly specialized deck guardrail testing equipment to help get a better idea of what 200 lbs of pressure felt like.  Jealous much?

Sunbeam Scale

Ok, it’s just an $8 bathroom scale.  After some playing around, I’ve learned that 200 lbs is about the most pressure that I can personally apply to the top rail of a guardrail, just by standing on the ground.  In the photo below I’m applying about 150 lbs of pressure, and I’m straining to do it.

150 pounds of pressure

The weakest point in most guardrails is always going to be at the end, where it terminates next to the house.  All that typically supports the guardrail at this location is the 4×4 post, assuming posts were used to construct the guardrails.   In the photo above, I’m pushing on the guardrail at the end.   This guardrail actually performed fairly well – most guardrails won’t tolerate nearly that much pressure.

The surest way to construct a guardrail that will withstand 200 lbs pounds of pressure is to use metal brackets that are designed just for this purpose.   A couple manufacturers that make such brackets are DeckLok and Simpson Strong-Tie.   If special metal brackets aren’t going to be used, the support posts should be constructed with full size 4x4s (not notched at the bottom), attached with through-bolts, and extra blocking usually needs to be installed to help keep the guardrail secure.

In the photo below, the ovals show where extra blocking was added.  This blocking tremendously stiffens the joist that the guardrail is attached to, making it so the guardrail won’t budge even when a full 200 lbs of pressure is applied.

Nice Guardrail

The bottom line is that weak guardrails are a safety hazard that should be corrected, especially on decks that are high above the ground.  For specific guardrail construction methods and rules, turn to page 15 of the  Prescriptive Residential Wood Deck Construction Guide.

May is Deck Safety Month – Related Post:

How to prevent your deck from collapsing: start by attaching it properly

Reuben Saltzman, Structure Tech Home Inspections – Email – Minnesota Deck Inspector



Deck Ledger Attachment Methods

May 8th, 2012 | 9 comments

May is National Deck Safety Month, so I’m going to start off this month by writing about the most common cause of deck collapses – improper attachment to a building.  Most decks are supported on one side by the building, and on the opposite side by the earth.  The photo below shows a deck collapse that happened here in Minnesota, and this is exactly how most decks collapse.  The cause of collapse is quite obvious – it wasn’t attached properly.

Deck Collapse

Is your deck properly attached to the building?  It’s not always possible to know for sure, but today I’ll discuss a few different ways of attaching a deck to a building.  The piece of wood that connects a deck to a building is called the ledger, or ledger board.  I’ll be using this term repeatedly.

Lag Screws

Lag Screw

Traditionally, lag screws have been the most common method of attaching decks to buildings.  To properly attach a deck ledger using 1/2″ lag screws, 5/16″ holes need to be pre-drilled through the ledger and rim joist.  After that, a 1/2″ hole should be drilled through the ledger only.   For specific spacing and installation instructions, you can turn to page 12 of the Prescriptive Residential Wood Deck Construction Guide.   There’s no way of knowing if all of these steps were followed just by looking at a deck, but if lag screws are visible, you can feel a little better about the deck attachment to the building.

Lag Screw Diagram

One problem that I occasionally find with lag screws is that they’re not attached to anything substantial behind the ledger.  When a home is constructed with floor trusses and there is no rim joist for the deck to attach to, it’s important to figure out what the screws are going in to.  In the photos below, the lag screws at this Eden Prairie townhouse were only attached to the fiberboard wall sheathing, which is basically worthless.  You wouldn’t want to put too many people on that deck.

Lag Screws at ledgerboard

Lag Screw in to nothing

Lag screws are fairly inexpensive, but they take special steps to install correctly.

Special Ledger Screws

LedgerLok fastener

Because of the tedious process involved in drilling several pilot holes in the wood to use lag screws, there are a few products available that are designed for the specific purpose of attaching a deck ledger to a building.  One such fastener is the FastenMaster LedgerLok®, which is pictured above.  Simpson Strong-Tie makes a similar fastener, called the Strong-Drive® SDS Screw.  These fasteners are designed to be installed without any pilot holes, and they already come with a washer attached to each head.

While these fasteners may cost a little more, they’re fast and easy to install, and they’re code approved to be used in place of 1/2″ lag screws.



Carriage Bolt

Through-bolts can be used to attach a ledger to the house when the interior of the rim joist is accessible.  This is typically done using carriage bolts, pictured above.   When through-bolts are used, you’ll either see the head of the bolt or the end of the bolt at the ledger.  Lag bolts work in a similar manner.

All things being equal, a through bolt makes for the strongest connection per fastener.  Without all things being equal, there are certainly ways of installing through-bolts improperly.  In the examples below, taken at a townhouse in Edina, you can see the end of the bolt where a washer and nut were fastened.  The problem with this installation is that someone didn’t have long enough bolts, so they had to chisel out a bunch of holes in the ledger to sink the washers and nuts in to.


Notched Ledgerboard

This is probably the least common method of deck attachment because it takes more time, and requires more running in and out of the building.

Nailed Ledgers

No nails

Nails are not an acceptable way of attaching a ledger to the building, because they can pull out.  I don’t have any statistics to quote, but this is probably the most common cause of deck collapses.  If you look at a deck ledger and all you can see are nails holding it in place, it should be addressed.  This is one of the most common deck problems that home inspectors find, and the repair is usually an easy fix.

Nailed Ledgerboard

Reuben Saltzman, Structure Tech Home Inspections – Email – Minnesota Deck Inspector


Inspecting Your Own Deck

May 3rd, 2011 | 9 comments

As I’m sure you already know, May is Deck Safety Month, so it’s a good time to talk about deck inspections.  Is your own deck safe?  Now is the time to check.  If you’re going to have a party or a large gathering, you better be sure.  The best way to be sure is to pack as many people on to your deck at one time as you possibly can, and have them bounce up and down all at once.  If your deck doesn’t collapse, it’s safe.

Collapsed Deck
Ok, that’s a joke.  Seriously, the best way to know about your deck is to have it professionally inspected. As I’ve said before, building a deck and replacing a water heater are two of the most common projects that get royally screwed up by DIYers on a regular basis.  If you’re not keen on hiring a home inspector or carpenter to check out your deck, there are still a few basic things that you can look for yourself.

Improper attachment to the house

The most common reason for deck collapses is improper attachment at the house.  That’s what happened with the deck pictured above.  If the deck is supported by the house, it should be attached with bolts, lag screws, SDS screws, or some other similar method.  The photo below shows proper attachment with lag screws, which I’ve circled in black.  This is the most common deck ledgerboard attachment method.  If you look at the deck attachment to your house and all you see are nails or small screws, you have a problem.  For a more in-depth discussion of different deck attachments methods, click here Deck Attachment Methods.

Lag Screws

Improper flashing at the house

There should always be flashing installed above the top of the ledgerboard – that piece of wood that attaches the deck to the house.  The purpose of the flashing is to keep water from leaking in behind the deck at the house and causing rot.  Here in Minnesota, painted galvanized steel is pretty much the standard way to flash the ledgerboard.

To determine if the ledgerboard is flashed, just take a peek underneath the deck.  If you can see a piece of metal sticking out over the edge of the ledgerboard from underneath, you know that flashing is present.  This doesn’t mean it was installed properly, but you should at least feel a little bit better knowing it’s there. If installed properly, this flashing will extend up underneath the siding.  The photo below shows what you should see if the flashing is properly installed; I drew a black rectangle around it.

Ledgerboard flashing

If there is no flashing present, there will be a much higher chance for water instrusion and rotting.

Improper joist hanger installation

Joist HangerJoist hangers are those metal brackets that attach the deck joists to the house and beams.  The manufacturers of joist hangers are very specific about how joist hangers should be installed; they specify exactly which nails should be installed, and exactly how much weight the joist hangers will support when installed properly.   Here are a few defects that I regularly find with joist hangers:

  • Missing nails.  Nails are supposed to be installed in every hole.
  • Improper joist hanger nails.  I find improper joist hanger nails on almost every deck.  If you can see a little “10” on the head of the nail, it’s probably the wrong nail.  Click the link above for more details on this defect.
  • Screws used instead of nails.  Screws don’t have nearly the shear strength of nails, and they’re not an acceptable substitute.  Well, there’s one screw I know of that’s an acceptable substitute, but I’ve never actually see it installed.  Joist hanger screw
  • Altered joist hangers.  Joist hangers shouldn’t be bent or cut.


Get a screwdriver and poke around your deck looking for rot.  The area that usually rots first is the place where two deck boards butt up against each other over a joist.  Pay special attention to that location.  If your deck doesn’t have the aforementioned ledgerboard flashing, you should also pay special attention to the place where the deck connects to the house.  The video below shows me inspecting a rotted deck in Minnesota last year.


Improper stairway attachment

The best way to attach a stairway stringer to a deck is to use a metal bracket that’s designed just for this purpose.  The photo below left shows a proper bracket for a stairway stringer.  This bracket isn’t the only way to properly attach a stairway stringer, but it’s probably the best way.  The photo below right shows an improper installation; they used a joist hanger bracket, and only managed to get a couple nails in the entire bracket.  Not cool, and not uncommon.

Stairway Stringer Bracket Improper stairway stringer attachment

Guardrail problems

Guardrails should be strong.  If you can push on the top of your guardrail and it moves a couple inches, it’s not strong enough; guardrails should be able to withstand 200 lbs of pressure along the top rail in any direction.  While this may seem like a lot, just think about a group of people leaning against a guardrail while heavyset guy who’s had three too many mint juleps falls against the guardrail.  If a guardrail is supported only with 2×2 balusters, it’s probably way too weak and should be reinforced.  You can read more about this topic at my blog about guardrail requirements.

Also, the current requirement for guardrails is that the balusters be spaced so that a 4″ sphere can’t pass through.  This is a requirement so little kids don’t get their heads stuck.  Common sense also tells you that you don’t want horizontal balusters that little kids can climb like a ladder, but there’s nothing in the building code that prohibits this design.

That makes up my list of the most common deck defects that you can look for yourself.  This isn’t a comprehensive list, but it’s a great starting point.  If you’d like a comprehensive but much less user-friendly list of things to look for while conducting your own deck inspection, you can download a deck inspection checklist from the North American Deck and Railing Association.

Reuben Saltzman, Structure Tech Home Inspections – EmailMinnesota Deck Inspections

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Coon Rapids Deck Collapse – Why It Happened

July 13th, 2010 | 5 comments

If you watched the news this weekend, you probably heard about the deck collapse that happened in Coon Rapids on Friday.  On WCCO news, they even had an expert speculate that the deck collapsed because it wasn’t properly secured to the house.  When I hear news stories about a deck collapses, they usually say they’ll come back to the story once they learn what the problem was, but they never do…

so I decided to inspect this Coon Rapids deck myself.  Here’s what I found:

Epic Fail

Coon Rapids Deck Collapse 1
According to WCCO, there were only five people on this deck when it collapsed.  The problem wasn’t that the deck was improperly attached to the house – this deck was completely missing a post.

I marked up two photos to show exactly what went wrong.  Click on the photos to get a large version.

Coon Rapids Deck Collapse Ledgerboard

Coon Rapids Deck Collapse Explanation

As you can see, one corner of the deck wasn’t help up by anything.  The floor joist that was closest to house is what was actually holding up that entire corner of the deck.  It’s a wonder this deck even supported it’s own weight.

While most advice about deck safety deals with proper bolts, nails, brackets, etc, it’s just as important to take a step back and look at the big picture.  Proper nails and bolts aren’t a substitute for a proper load path back to the ground.

Reuben Saltzman, Structure Tech Home Inspections – Email – Minnesota Deck Inspections

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Common Deck Defects

May 16th, 2009 | 1 comment

May is the North American Deck and Railing Association’s Deck Safety Month.  This gives me a great opportunity to talk about what I look at when I inspect balconies and decks in Minnesota, and what the most common defects are.

It’s estimated that of the 40 million decks in the United States, only half are built to code.  As a side note, building to code means you’re doing the worst job you possibly can, while still being legal.  The building code is a minimum requirement, and building ‘to code’ is not something to brag about. From the thousands of home inspections that I’ve performed, I’d agree that at least half the decks I look at have issues.  Decks are a part of a house that many homeowners feel qualified to build themselves, permits are frequently not pulled for the work, and the work may never get inspected.


Deck with an improper load transfer

The most common cause of deck collapse / failure is lack of proper attachment to the house.  This is also one of the most common defects with decks that I find!  The deck rim (or ledger) needs to be bolted to the house to keep it from falling away, but is frequently just nailed.   A few of the other most common defects that I find are missing nails in joist hangers (brackets that support the floor structure), missing flashing at the rim (metal that keeps water from leaking in to the house), and improper load transfers.   The photo at right illustrates an improper load transfer – look closely at the top of the stairway and ask yourself, what is supporting the landing at the top of the stairway?  This deck needs repair by a professional contractor.

While many decks are improperly built and remain in tact for a long time, what leads to failure or collapse is typically a change in use, which happens when there is a change in ownership.  Grandma and Grandpa have had the deck for 10 years and haven’t had any problems, but when a new family buys a house and has their first housewarming party, it might be the first time the structure of the deck is really even tested.  This is why decks receive particular attention during home inspections.

I also happened to do a story on balcony and deck collapses last year with Fox 9 News, which you can view below.

Reuben Saltzman, Structure Tech Home Inspections – Email - Minnesota Deck Inspections