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Options for Fastening Deck Posts to Footings



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so the post the footing connection is

super-important for a couple of reasons

this has to resist both lateral loads

and uplift loads lateral loads of those

that you can think of a riding lawnmower

backing up into a post and if we weren't

anchored down it could kick that post

off and the deck could fall on up lift

loads I would be like a high wind from a

hurricane or even a heavy thunderstorm

that could actually lift the deck up off

of the concrete footing so by having a

mechanical anchor to tie that down we're

going to resist those loads and be able

to keep the whole deck stable now

they're a bunch of different options and

we'll walk through each of those so you

got see what your choices are starting

with retrofits so if you already have a

deck that has a six by six or a four by

four posts down on top of a pier and you

want to secure that down in place so it

doesn't get moved you can take some of

these retrofit post connectors they're

going to just go right around the side

of the post we get screwed in with some

structural screws to the sides and then

some structural concrete screws down

into the concrete securing that post

down now if you've got a big six by six

you might put four of these on if you

have a four by four which is a little

smaller to is going to be more than

adequate so one of the most robust

connections you can make is a

cast-in-place post base these are going

to have an open hollow area at the

bottom below a standoff that you're

going to imbed down into the concrete by

suspending this in the footing form

before you pour the concrete preferably

you can install them after you've poured

the concrete but in that case you have

to make sure you use a vibrator to get

the concrete to flow evenly through and

under that standoff now these are super

heavy duty and they're tricky to install

the way most contractors will install

them to get the most accuracy is to

actually frame the deck put the post in

temporarily securing them in place with

some temporary supports supporting the

beam and then you attach this to the

bottom of the post over the footing hole

and then pour the concrete that way

there's no mistake and where they're

going to be located where I use this

type of connector more

frequently that other connectors is when

on building a roof over a deck I've got

additional uplift loads that have to be

accounted for when you have a roof and

that's going to be transferred through

the post down to the frame of the deck

then through the post down to the

footing this type of connector gives us

a lot more uplift capacity than some of

the others I'm going to show you so

probably the most common type of way to

anchor into concrete footings is to use

a anchor bolt or a J bolt these are cast

in place when the concrete is being

poured the nice thing about them is

they're relatively inexpensive but they

give us really good uplift capacity

there's a bunch of different pieces of

hardware we can make for the connection

between the bolt and the footing to the

post but each of those only gives us a

little bit of lateral movement in and

out or left and right and that's

dictated by the slot so you still have

to be really close when you're

installing these in locations so that

you can make sure that the post when it

comes down is going to fit right in the

socket of that anchor let's look at the

bottom of a couple of these so you can

see how that comes into play this one

for instance has an l-shaped slot that's

going to enable us to move in and out

about an inch inch and a quarter or if

we turn that 90 degrees is going to be

an inch and an inch in corridor left or

right so that gives us quite a bit of

movement some of the others don't give

us quite as much they're gonna have just

a small slot so that might be something

you take into consideration when you're

looking to a piece of hardware in

addition to some other features like the

gauge of the metal how thick it is how

much uplift capacity it has and how much

lateral resistance capacity it has

that's all going to be based on the

height of your post or the exposure you

have to high winds owns now all three of

these have a standoff in the middle and

these are important you can get

connectors that will actually let the

wood post sit right down on top of the

concrete or very close to the concrete

the trouble with those is that any water

that settles on top of the pier or wicks

up through the concrete can get sucked

up by the end grain of the of the wood

post and then increase the chance that

you could get that post rotting out

with that one-inch standoff that water's

gonna tend to drain away it's also gonna

dry a little bit quicker and you're not

in direct contact with the concrete so

the woods gonna last a lot longer longer

lifespan on the deck for what you're

spending the money on now these come in

both 4x4 and 6x6 sizes one of the

features on some of them where they have

the upturn leg is they've got good

height connection on the post and

they'll come with some structural screws

we can connect those others have an

upturned leg that you get three sides

that are already bent into position so

when you set the post in you've got a

way to slide that in and then you turn

this final leg up and then dry fasteners

in to secure it so there's a lot of

different options with regard to the

hardware let's take a look at some of

the anchors that we can use to connect

to these connectors to the concrete in

the event we didn't cast a J bolt into

the concrete when we initially did the

footing so some of the anchors we can

use that if in the event that we didn't

put a J bolt or an anchor bolt cast down

into the concrete or some structural

hot-dip galvanized screws you're going

to want to make sure that if you're

going to use these you check with the

manufacturer to make sure that these are

compatible with both pressure treated

lumber and the hardware you're going to

be installing because some can be

installed in exterior applications and

some can't and some different ones are

going to be a problem if you do actually

will fall apart so what you need to do

is bore a hole with a hammer drill into

the concrete a little bit deeper than

the depth of these screws and you're

going to need to blow that hole out and

then you can drive that screw right in

the beauty of these is that they're

simple to install and you can precisely

locate that anchor underneath where the

post is going to be you don't have to

rely on doing that at the casting point

when you're pouring the concrete way as

you do with the J bolt another option is

wedge anchors now these wedge anchors

have a collar at the bottom which

expands to grip the side of the concrete

hole that you've drilled in the in the

footing of the pier

after you've installed it so you drilled

the right size hole usually it's a half

inch hole if you'd got a half inch bolt

you drop that down and then as you crank

down on the nut it will draw up the

friction on the side of that hole will

expand that wedge

it'll secure this down remarkably these

have a really good capacity for uplift

more than I would have ever expected and

all of the specifications for that are

outlined in the manufacturer's guide so

you can look to those to find out if

you're trying to meet a certain uplift

capacity what those would be with all of

these fasteners as I'm going through

them one important thing to note is the

concrete itself you might be inclined to

use these when you initially pour the

concrete say a day or two later when

you're ready to frame the deck but you

don't want to do that you want to wait

until that concrete is cured that may

mean that you have to temporarily

support that deck and wait 28 days till

the concrete is cured before you use

some of these systems so check with the

manufacturer to see if there are any

limits to the how old the concrete is to

make sure it's not too green and tend to

crack in the event that you use these

before they're cured the last option is

a chemical option these could be an

epoxy adhesive and are acrylic adhesive

and these have gonna Bowl tubes where

there's actually two components inside

of the the tube either with separate

tubes or a uni tube and then once you

put that nozzle on the front there are

little convolutions in that tube as it

exits out the front that are mixing the

acrylic with the hardener or the epoxy

with the hardener so that when you

inject this into the hole it's going to

be ready to set in probably a couple of

hours depending on the temperature there

are key installation details you want to

check from the manufacturers

installation instructions but some of

the big ones are making sure the hole is

clean before you actually install this

that means brushing and blowing it out

then after you insert the adhesive you

just drop the threaded rod in and then

you can start to set the anchor you just

can't tighten up on the top of that nut

after that's had enough time to cure

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