Deck and Cinder Block Wall
NotYoungButStupid
| Posted in Construction Techniques on
I have a hollow cinder block wall to which I want to attach a deck. For multiple reasons I am trying to avoid digging foundation posts right up against the house. (The ones on the other side of the deck will be o.k. to dig and install). Are there any possibilities here on how to attach this girder to house without new posts? Is filling in the cinder block even a option here?
Replies
How close can you dig to the house?
Enough so you can cantilever the frame to the house with no connection?
While filled block would hold the deck connection “up”, I’d be concerned with force on the block in/out. Horizontal rebar laid in conjunction with bldg the wall might have resisted that force. But then again, never run into that problem nor am I an engineer.
The closest I can dig would probably be 3 feet away and that’s the edge of the hole and not the center. I am estimating a 12”-18” diameter hole will be needed.
https://www.awc.org/codes-standards/publications/dca6
(you may have read it)
https://www.finehomebuilding.com/membership/pdf/385972/021282054.pdf
has a hint.
https://www.strongtie.com/screentubes_adhesiveanchoringaccessories/steel_screentube/p/steel-adhesive-anchoring-screen-tubes
https://www.finehomebuilding.com/membership/pdf/385972/021282054.pdf
has a hint at the end. adhesive and screen tubes.
An example of hollow wall anchor screens:
https://www.strongtie.com/screentubes_adhesiveanchoringaccessories/steel_screentube/p/steel-adhesive-anchoring-screen-tubes
and you need some adhesive to go with it.
https://embed.widencdn.net/pdf/plus/ssttoolbox/zjc7nxkcoh/S-A-PG19.pdf?u=cjmyin
see page 34
Note that these are not on the approved list, which is included in the fairfax county document mentioned later.
Hilti screen and adhesive is on the list:
https://www.hilti.com/c/CLS_FASTENER_7135/CLS_INJECTABLE_ADHESIVE_ANCHORS_7135/r8298802
https://www.hilti.com/c/CLS_FASTENER_7135/CLS_ANCHOR_RODS_ELEMENTS_7135/r2804
as is the read head
https://www.itwredhead.com/products/adhesive-anchors/a7
https://www.itwredhead.com/Portals/0/Documents/2019%20Catalog/Adhesive%20Anchoring%20Systems/Umbrella%20Inserts%20and%20Screen%20Tubes.pdf
Building codes prohibit attaching deck ledger to hollow block walls. However, attachment is allowed to a block wall if the cores are grouted solid with concrete. It's all in this document. https://www.awc.org/pdf/codes-standards/publications/dca/AWC-DCA62015-DeckGuide-1804.pdf
The end of Mike Guerten's article (post #3 above)
last paragraph in figure:
"Fairfax County also permits ledgers to be fastened to hollow CMU using adhesive anchors and a “screen” (mesh tube) on the inside to retain the adhesive. Follow the adhesive-anchor-system manufacturer instructions."
https://www.fairfaxcounty.gov/landdevelopment/sites/landdevelopment/files/assets/documents/pdf/publications/deck-details.pdf
See page 15 of 28
The next page identifies anchor sources which are approved. These do not include the ones I pointed to earlier as examples.
Of course, the code in the jurisdiction of the deck in question applies.
I'm surprised Fairfax County allows that - They're about the strictest jurisdiction in the country.
I suspect there were some interesting conversations.
I've had too many CMUs fall apart from putting in tapcons to be able to trust this, no matter the engineering standing behind this.