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The following article was written by deck inspection expert and long time Massachusetts home inspector Bob Mulloy. Written specifically as a guide for home inspectors to follow when inspecting decks, it is also a very useful primer for home owners who need to know what to look for when self-inspecting their own deck.
PLEASE NOTE: Annual deck inspections by a professional inspector are strongly recommended to help prevent major deck related accidents.

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Or Can They?

By Bob Mulloy

So, you walk around to the rear of the home and there it is - the deck! Every home nowadays just has to have one, and if one is not present, that seems to be no problem for the homeowner. They just buzz down to the local "you-do-it-center", pick up a load of lumber, and bang it together. Bingo, a deck is born! Or, the less handy homeowner might hire Mr. Flybynight, the carpenter who can certainly build a quality deck for a song and a dance.

Does the latter scenario sound familiar? Now we come to the thrust of this article, for as you know, we home inspectors must evaluate the deck and prepare a final report for our clients which includes our observations regarding the deck, along with the rest of the home.

Where to start? Let’s approach a deck inspection methodology by asking ourselves several pertinent questions:

FOOTINGS - Do the footings appear adequate? I like to inspect the deck from the ground up. I start by examining the visible piers or footings at ground level. If I find patio blocks, cement blocks, or five-gallon buckets filled with cement, then I automatically think "red flag" and investigate a little more carefully by probing. Up here in New England, all footings must extend a minimum of four feet below the ground to prevent frost heave, but all to often I must document "shallow footings beneath deck, potential for frost heave movement." You might include a disclaimer at this point: "DISCLAIMER: The actual depth of the footings that support the deck is undetermined and can only be determined by excavation and measurement."


Finding any visible shortcuts causes my inspection antennae to go up. I start wondering just who built the deck, the owner or a contractor, and why were these errors allowed? Was a permit pulled? Shift the burden of proof from your shoulders to the client's by suggesting that your client do a little research at the local building department.

While our focus is under the deck, how many times have you seen a crater beneath the deck that will retain surface water & roof run-off that will soak into the ground and end up in the basement? How many times have you seen vegetation left under the deck? How many times have you seen a dryer vent terminate under the deck? How many times have you seen the deck built right over the septic tank or the basement entrance or the oil fill & vent pipes? There are many things to consider that can be easy to miss.


SUPPORT - What holds the deck up? Working upwards in inspection methodology, the next components encountered are the columns or support posts and beams. I like to sight down the line of support posts from several vantage points to see if the posts are out of plumb, missing, improperly spaced, or excessively notched. If the support posts are wood, out comes my probe again as decay is very prevalent with wood decks. Some of the deficiencies I see in the area of support posts are downright scary when you think that the deck may be asked to support the weight of numerous people during a cookout.

Next, I check the base of each post to see if it is buried within the concrete footing, whether the post falls properly upon the footing and how it is attached. When posts are buried within the concrete, decay is likely in the future even if the wood is pressure treated. More importantly, the concrete footings are likely to blow apart from frost heave because the wood shrinks allowing water to enter each posthole.

OOOOPS! - They missed by 8”.

I like to observe a posts that fall squarely upon the footing and do not dangle half off in space using a skyhook for bearing. Better still are post brackets that provide a means of anchoring between the footing and the post while separating the two to prevent decay.

When the posts fall beneath a beam, I like to see a top plate that anchors the two components together, or at least a proper nailing schedule. The presence of extra posts, sticks and braces usually indicate original poor workmanship and attempts to stabilize the deck frame from movement.

When the support posts are also used to support a let-in rim joist, floor joists and railing posts, then a whole new series of defects may be present. Over-notching or improper notching seem to be frequent flyer problems. Sometimes, notches are cut too deep and the remaining wood is drilled out for bolts, leaving posts that easily wobble when the guard railings are tested with lateral pressure. Imagine someone leaning on the guardrail and the post suddenly breaks in half where it is notched! Ouch!

Built-up beams frequently rest upon the deck posts. The beam may be situated at the outside edge of the deck or several feet back to create a cantilevered effect. The problems with the built-up beams seem to fall within categories of improper splicing and inadequate nailing. Quarter-point splicing is best and the splices should fall above a post. However, Mr. Do-it-yourselfer can stretch a 2 x to infinity and beyond with no regard for load bearing, bending or potential collapse.


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Bob Mulloy is President of Allsafe Home Inspection Service, Inc. in East Bridgewater, Massachusetts, and a national presenter on the topic of deck failures. He is a licensed Massachusetts home inspector, a member of the American Society of Home Inspectors (ASHI), and Chairman of the Education Committee for the local ASHI NE Chapter. Bob is also a Massachusetts Board approved continuing education provider for home inspectors. He can be reached at 508-378-7170, by email at rmulloy@verizon.net, or via his website at:


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