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Crawl Space Beam and Joist Support Questions


Sequoia's Avatar
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Join Date: Jan 2007
Posts: 96
CAL

06-22-09, 01:51 PM   #1  
Crawl Space Beam and Joist Support Questions

Our townhouse experienced significant damage to the framing in the crawl space due to water infiltration. We spent the last two years investigating where the water was coming from and believe we have done all that can be done to eliminate the sources. With that resolved we moved on to rebuilding the foundation and framing in the crawl space.

We were in the process of replacing some rotted floor joists and decided to replace the entire support structure for the landing after seeing the extent of the rot and poor condition of the piers.

I have some questions regarding how much end bearing is required for the ends of joists and beams and the best method of terminating a beam at a CMU wall.

Regarding end bearing for joist and beams. I found the following in Principles of Home Inspection: Systems & Standards.

Joists require 1 1/2 inches of end bearing, considerably less than the 3 1/2 inches required for beams. That's because the live load carried by individual joists is much smaller than the beam's load. Note: Some jurisdictions call for 3 inch end bearing on masonry. Check standard practices in your area.

Where joists rest on beams, best practice is to have the joist rest on the full width of the beam, rather than just 1 1/2 inches. Good practice also includes splicing joists that overlap from opposite side of the beam.


Based on the above I believe I should go with the following:

ORIGINAL FRAMING Only 1 of joist bear directly on 4x6 beam.

Click link: http://www.fototime.com/7D02FCEE01A6ED3/orig.jpeg

Photo below show typical condition of the original joist after I removed the rim joist.




PROPOSED REVISED FRAMING 3-1/2 of joist bare directly on 4x6 beam.

Click link: http://www.fototime.com/510E5027526A10A/orig.jpeg

Last week we poured new footings and pilasters for the posts that will support the middle of the new 4x6 beam and floor joist. The new 4x6 beam will replace the existing 4x6 beam and plywood shown in the original framing drawing above.



I would like to support one end of the 4x6 bean with a Simpson HU46 hangar nailed to the 6x6 beam that replaced the rotted triple 2x6s. This will leave a gap between the new 4x6 beam and an existing 4x6 beam below.



The other end of the 4x6 terminates at a CMU wall. Currently it bears 1 on a pressure treated 2x6 secured to the CMU wall with corroded pins and washers.



I believe I have three options that meet code.

1. Remove the current pressure treated 2x6 ledger and secure the end of the new 4x6 beam in a Simpson HU46 secured to the CMU wall with Simpson Titen screws.



2. Remove the current pressure treated 2x6 and replace with another pressure treated 2x6 that is located 5-1/2 higher and secured to the CMU wall with expoxied 5/8 bolts, washers and nuts. The new 4x6 beam would be secured in a Simpson HU46 secured to the new pressure treated 2x6 with 1-1/2, 9 gauge, HDG nails



3. Remove the current pressure treated 2x6 and replace with a pressure treated 4x6 secured to the CMU wall with expoxied 5/8 bolts, washers and nuts. This will allow the 3-1/2 of the new beam to bear completely on the new 4x6 ledger as recommended in Principles of Home Inspection.

Comments appreciated.

 
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Pulpo's Avatar
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06-29-09, 07:35 PM   #2  
There is something I don't like about option 1, with the hanger bolted directly to the block. I vote for 2 or 3.

Don't forget to use all zinc plated hangers (zmax) since the chemicals in presure treated wood have changed in the last few years.

 
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