Reuben's Home Inspection Blog


Deck Inspections: Is Your Deck Properly Attached To The Building?

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


Comment balloon 22 commentsReuben Saltzman • May 08 2012 03:21AM


Great information! I had this issue come up a few months back with the lag screws. Thanks for sharing!

Posted by Donna Derrick Ponte Vedra Beach, Jax Beach FL (Davidson Realty Inc) almost 8 years ago

Thanks, Donna.   This has to be one of the most common issues that home inspectors report with concern to decks.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 8 years ago

Another super blog Reubs!  Lags are no longer approved here and the through bolts used are looked at from inside by the county to insure they are into the rim joist, and need to be 8" apart and in a W pattern. 

And I've seen that deck before!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) almost 8 years ago

Hi Reuben - It seems that too many deck inspections show just what you are talking about--especially on older decks. They used nails to attach it to the house and that doesn't last long. I wouldn't want to be on that deck.

Posted by Peggy Chirico, REALTOR® 860-748-8900, Hartford & Tolland County Real Estate (Prudential CT Realty) almost 8 years ago

Thanks for the great info there Rueben.  Pretty scary to see a deck collapse.  No fun there.  

Posted by Amanda Christiansen, Christiansen Group Realty (Christiansen Group Realty (260)704-0843) almost 8 years ago

Great information Reuben,  a chain is only as strong as its weakest link...

Posted by Chris Smith, South Simcoe, Caledon, King, Orangeville Real Esta (Re/Max Chay Realty Inc., Brokerage) almost 8 years ago

Thanks for the information. I will alert buyers to take a closer look at the deck  when we look at homes. I always recommend a home inspection.

Posted by Gita Bantwal, REALTOR,ABR,CRS,SRES,GRI - Bucks County & Philadel (RE/MAX Centre Realtors) almost 8 years ago

Wow - Great post.  I cant believe sometimes what people think is acceptable. 

Posted by Brandon Acken (RE/MAX Preferred Professionals) almost 8 years ago

Reuben, when I built my deck, the County was very specific how the ledger board should be attached. In my case it was attached to a concrete wall. I used expansion anchors. The deck hasn't moved in 30 years.

Posted by Michael Setunsky, Your Commercial Real Estate Link to Northern VA almost 8 years ago

Very important topic. Several people were injured and a couple killed a few years ago in Atlanta when the deck, which was improperly constructed and overloaded, collapsed and dropped a significant distance.

Posted by Ron Barnes, "Most agents claim they're #1 - I THINK YOU'RE #1! (Associate Broker at Berkshire Hathaway Home Services Georgia Properties) almost 8 years ago

Excellent post again!  That photo you included should make anyone pause when thinking about the safety of their deck.

Posted by Kathryn Maguire, Serving Chesapeake, Norfolk, VA Beach ( (757) 560-0881) almost 8 years ago

I had a chance to view this subject up close recently as I supervised the remodel of a deck. The stringers and the joist hangers play a huge role in how things will turn out. Replaced several rotting pieces of woods and inspected the rest...happy ending. Good lesson post thank you Reuben

Posted by Richie Alan Naggar, agent & author (people first...then business Ran Right Realty ) almost 8 years ago

Decks that are built up high do scare me.  It is amazing how many people just hire anyone to build a deck.  Also, I wonder how much inspectors look at this in general home inspections.  

Even large deck contractors sometimes hire subcontractors that cut corners.  With this information, we can at least know what to look for.  Thank you for ths informative post.

Posted by Athina Boukas, Certified Residential Specialist (CRS) (Virginia Capital Realty) almost 8 years ago

We have all heard of tragedies - sometimes fatal - when decks collapse.    Thanks for the great photos and great explanation, Reuben!

Posted by Fred Griffin Tallahassee Real Estate, Licensed Florida Real Estate Broker (Fred Griffin Real Estate) almost 8 years ago

Good points Rueben.  I have Bolts and lag screws just depending on the location and what I could access.

Posted by William Feela, Realtor, Whispering Pines Realty 651-674-5999 No. (WHISPERING PINES REALTY) almost 8 years ago

Reuben, Awesome blog. I have never seen a deck done right, well except for the one I did  ; )

Now seriously I have seen them with proper lag and no flashing, and I have seen them with flashing and no lags, and I have see them try but no cigar. Then we get into bracing when they get higher and we add another complexity... oh yeah add the guardrail and stairs oh boy!!

With that being said I just never see them cover all the bases. It always makes me scratch my head. They really are just not that hard to build or are they?

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) almost 8 years ago

Another great post. I just inspected a deck, are you ready for this, without any issues. The ledger was double through bolted to the house. 6x6 piers attached to large footings, guardrails correct and strong. The homeowner built the deck, but has a background in construction. In fact it turned out he used to work with an inspector I know. Small world. 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) almost 8 years ago

Jay - thanks bud.  Lag screws really aren't allowed in your area?  That's crazy!  What about the special fasteners made just for deck ledgers?

Peggy - me neither!

Christiansens - I'm glad I've never been involved in one.

Valerie - thanks, and I think I know what you mean.

Chris - that's exactly right.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 8 years ago

Gita - that's good advice for your clients.

Brandon - thanks.  Me neither.

Michael - concrete anchors aren't commonly seen, but they work very well.

Ron - we seem to get a few stories of injuries caused by deck collapses here in Minnesota every year.  I can't remember the last time there were any deaths though.

Kathryn - thanks.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 8 years ago

Richie - thank you much, sir.

Athina - from what I know, decks are looked at very closely by most home inspectors.  It's the one area that we consistently find problems.

Fred - thanks for reading.

William - it sounds like you shouldn't have much to worry about.

Donald - apparently, they're extremely hard to build correctly!  

James - get out of here.  I don't think I've ever found one :)

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 8 years ago

Ain't heard...

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) almost 8 years ago

Great info and timing.  My buyers home inspection just showed that the deck was in really bad shape, seller denies any problems.  Clearly after seeing your information the deck truly is in bad shape.  Thank you

Posted by Kim Boekholder Utah Real Estate, Broker, Results Real Estate (Results Real Estate 801.580.5624) almost 8 years ago