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Troubled Houses - A Home Owner's Resourcesm - Decks
We see many interesting adverse conditions during our inspections, partly because of the unlimited number of ways people can mess up a house, but also because we do a thorough inspection to reveal these adverse conditions. We hope these stories help home owners avoid these costly conditions by learning about causes, preventions, and remedies.
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"Troubled Houses - A Home Owner's Resource" is a SERVICE MARK of Hankey & Brown Inspection Service Inc. Click here for the list of topics and all articles in this resource.
Is your deck built properly? Click here for more information.
We offer deck inspections for home owners. Shown below are examples of what we find.
Very Insecure Deck railing
Potential deck collapse averted by home inspection
Details Matter: A screwed up deck
Faith in Bolts - Deck beam
Double decay - Wood deck built atop a timber wall
Clear View Deck Railing – It’s what you don’t see that matters
This 4 year old wood frame deck has a beautiful clear panel railing system that overlooks a lake and wetland.
The deck planking is a synthetic wood composite of extruded planks with a wood grain top surface and an extruded ribbed “m” shape underneath.
The deck rail posts are secured with four fasteners in a welded metal flange at the base of each post. The railings moved easily with hand pressure applied to the toprail.
Unfortunately, the deck builder failed to realize the inherent weakness of the deck planking as an attachment point for the flange fasteners. Each flange had only two of the four screws into the deck framing. The other two screws went into the deck planks, often into the thinnest portion of the planks.
The railings on the stairs were about the same. Two screws at each rail post flange missed the stair framing and went into the tread planks only. Also, the riser material was not suitable for exterior use and was already water damaged.
Our report listed the entire deck railing system as an adverse condition since the railing attachment was not consistent with good and established practice and has a potential for failure under lateral loading. We recommended immediate correction by a qualified deck builder. One possible remedy would be to remove all the fasteners that go into deck planks only, install solid wood blocking below the deck at each post location and re-install the screws into the solid wood. Alternatively, a bolt and large washer system might work, but the goal is to achieve a deck railing system that can withstand a 200 lb. lateral force applied at any point along the top of the railing.
For more information on deck railing inspections see the North American Deck and Railing Association (NADRA) web site at http://www.nadra.org/consumers/deck_inspections.html
Deck framing and railing connections are often made stronger with the use of metal fasteners made by Simpson StrongTie or DeckLok. Both manufacturers websites include good illustrations on deck construction. Another resource for good deck construction methods is the American Wood Council. They have a Prescriptive guide for deck construction.
Potential deck collapse averted by home inspection
This beautiful deck is attached to the rear of a lovely suburban two story home built in 2003 (deck built 2004). Initially, our inspection revealed a common adverse condition in the deck railing. The railing was comprised of metal grills between wood 4x4 posts. Unfortunately the posts were notched and bolted to the frame through the notched portion.
This creates a very weak post that has a high potential for splitting at the notch. This type of post has been thoroughly tested at Virginia Tech and found to failure the strength requirements for deck railings.
We became more concerned when we examined the unfinished basement wall near the deck and saw large lag screws penetrating into the rim.
We do not normally see the interior ends of bolts or lag screws used for deck ledger attachment, so this caught our eye and lead us to examine the ledger attachment more closely.
The exterior view indicated that a reasonable number of lag screws had been used to secure the ledger board to the house, but we were not certain that those screws were into any suitable structural member. We returned to the inside and cut a test hole into the foil faced foam insulation in the rim to determine the material behind the ledger board.
We measured the top plate of the wall and the insulation thickness and determined that the material shown in the insulation cutout was 1/2 inch oriented strand board (OSB). Therefore, the lag screws were providing very little strength to hold the deck ledger (and deck) to the house. Good and established practice for deck ledger attachment in this case would have been to install the lags screws into the ends of the wood web floor trusses. (If approved by the wood truss fabricator).
In fact, we later learned that this plan had been approved by the truss fabricator and the lags screws were simply installed without checking that they were installed into the truss ends. The deck had passed a municipal inspection with this serious weakness. Our client requested a correction and additional lag screws were installed into the ends of the trusses. Click here to read the deck post testing article from Virginia Tech.
Details Matter: A screwed up deck
This deck covered the entire rear wall of the house. See the detail photos.
 
Screw taken from a joist hanger. Detail of joist hanger & screws.
Nearly all the joist hanger fasteners were 3/4" sheet metal screws, creating a weak deck-to-house connection with a high potential for collapse. Our client was advised to consult a qualified carpenter for immediate correction. See http://www.safestronghome.com/deck/
Faith in Bolts - Deck beam
 
This deck looks useable from a distance, but up close it has an important structural element that is not correctly constructed. The deck beam, composed of two 2x10's is not bearing on the column. Rather the 2x10's are BOLTED to the sides of the columns. Therefore the deck is supported by a few bolts rather than on a continuous load path (wood on wood on concrete footing).
Deck structure - Decayed frame on top of decayed timber
The owner of this 1985 built home was informed by a prepurchase inspection that the deck and screen porch below had some structural concerns. Our role was to further diagnose those conditions. The photo above shows the deck with clear panel railings, screen porch below the deck, and timber retaining wall supporting the deck and the fill beneath the porch.
The supporting columns for the deck bear directly atop the 25 year old timber retaining wall which has many decayed timbers. This decay was particularly troubling at the uphill end of the wall.
This column bears on the decayed end of the timber wall. The column base is also decayed. The column has moved and tilted as shown below.
 
The deck also had water damage/decay in the beams that sat atop these columns, due in part to the lack of a rain gutter on the rear eave above the deck.
 
The deck railing posts were fastened to the deck with 4 screws through the white metal base flanges. The two inner screws in each flange penetrated the deck boards only, making the railing extremely weak. (See similar case described above). Our recommendations were to consult an engineer specializing in retaining walls and a qualified carpenter to replace all decayed wood. Ideally, the deck should bear on concrete footings independent of the retaining wall. A rain gutter on the rear eave would reduce the potential for water damage to the house and deck. Click here for more information on this topic and a brochure on proper deck construction from the American Wood Council. Return to top of article list.
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