WOOD POST EMBEDDED IN CONCRETE

[STR04]

I have to design a 10’ tall (cantilever) privacy fence and was wondering how to fix an 8x8 timber post to a 24" diameter concrete pier. What else can you do other than embedding the post in the pier? This structure is temporary only needing to withstand 5-yrs of service and I would like to keep this economical (residential feel). Does anyone have any suggestions?

TIA

 

[egildea]

Embedding the post seems to be the best option, otherwise you will have to fabricate some base plate detail to attach to the pier that will house your post. Seems like a bit of over-kill to me. Embed the thing. If the client wants rid of it in 5 years, he can chop the top of it off and put a light screed over the top to mask the evidence.

 

[boo1]

Typically we spike the post to lock it in the base. Slope the top away from the post a few degrees to keep water away. Keep the post bottom a few inches away from the dirt. For a 10" privacy fence, 8x8 w 24" pier seems an over kill!

 

[SacreBleu]

The post will expand as it absorbs moisture and crack the pier. It may be a good idea to put in a #3 square or hoop tie.

 

[IFRs]

My neighbor embedded fence posts in concrete and the wood rotted away within 2 years. Best stick with pressure treated or get a good recomendation from both the wood and concrete people.

 

[whyun]

Using an embedded HSS sleeve may be considered.

 

[rday]

For fence posts I would dig the post hole, set the post and fill with gravel. Once compacted it functions every bit as well as cracked unreinforced concrete in this application. It also has the advantage of being free draining. It would also make removal of posts easier if required as digging out the gravel is easier than concrete. I would also go a little deeper than 24", but I have frost to consider as well as pretty high wind.

Rik

 

[boo1]

the 24" was Dia

 

[rday]

Oops, Your right Boo1. Thanks for the correction. I do agree with you that 24" diameter seems excessive.

Rik

 

[cvg]

never embed a wood post in concrete. Most codes do not allow this anyhow. I wouldn't recommend burying below ground either. Use the concrete base and a steel bracket anchored in the concrete. This is a fairly standard item available at Home Depot.

 

[dbuzz]

Like cvg, I would avoid embedding wood posts or columns in concrete.

If you must, ensure that you use pressure preservative treated wood.

 

[STR04]

Wow...quite a range of answers here. I truly appreciate the responses but it just reaffirms my original thought of "I don't know". I guess it depends on how you like to mitigate your losses here. To clarify the design an 8x8x10'-0" post 8'-0" O/C is required by design for douglas fir south No. 2 for 14psf wind pressure and a 2' diameter pier is also required based upon 200pcf passive pressure per IBC 1807.2.9