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First pavilion. Looking for advice.

Started by thebigrlebowski, July 29, 2021, 10:38:21 AM

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thebigrlebowski

Hello all,
This is my first time posting on this forum and I appreciate any feedback.
I'll be upgrading from building with lincoln logs with my son and plan on building a pavilion in our back yard for an upcoming hot tub.
I'm looking for any kind of advice and would like to ensure I'm building it beefy enough.  Specs are below.

Material - Rough-sawn western red cedar. All sizes are true measurements.
Location Ft Worth, Tx.

Pad size - 16' x 16'   4 inches thick with 12"x12"x12" footings under each post.  3/4 inch rebar spaced every 16 inches.
Post size 6" x 6" x 8'
Posts connected to concrete with Simpson strong-tie post bases and 8" Titan bolts.
side beams 6" x 10" x 16'
Front and rear beams 6" x 10" x 9'2".
Ridge Beam 6" x 8" x 16'
King posts 6" x 6" x 1'1"
Knee braces 4" x 4" x 2'6"  that span 1'10" from the post.
Rafters 2" x 6" x 8'6"   spaced 18 inches on center.  Will overhang 3'1" to create an eve and provide weather protection over wood boxes/countertops for future fireplace.
Roof decking 2" x 6" x 16' tongue and groove
Roof material felt under asphalt shingles

Roof sq ft 272
Snow load for this area 5 psf
estimated dead load 2000 pounds.  Used 23 lbs per cubic foot for wood(debatable) and 200 lbs for shingles and material.

Simpson strong tie straps will be used to connect beams to posts.  The beams will be set on top of the posts. The side beams will be notched 2 inches deep to allow for the front and rear beams to be seated.


The span for the front and rear beams will be 8'10" measured from inside edge post to post.
The span for the side and ridge beam will be 14'6" measured from inside edge post to post.
All beam, post, rafter, etc connections will be made with Simpson strong tie structural wood screws.

A fireplace will be a future addition and will have a footing 12" deep the size of the fireplace.

I've considered routing out a spot or 3 on the ridge beam to embed junction boxes for a fan or light so they could sit flush. The depth would be 1.5".  
1/2" conduit would be run along the top of the ridge beam to stay concealed and then through the beam to the junction box.  I'm wondering if this would weaken the ridge beam too much though.


 

 

 

 



 

Don P

Welcome to the forum,
Loads, I'd call it 10 psf dead and 20 psf live (wind controls below 20 psf snow). 30 psf total.

The ridgebeam tributary width in span, for checking bending strength and deflection is the swath ~9' wide x 14.5' long x 30 psf=3915 lbs
This would be the right calc for that;
https://forestryforum.com/members/donp/beamclc06b.htm
For the ridge I get a pass at 6x10 in #1 WRC.

The total load on the king posts is the swath ~9' wide x 16' long x 30 psf/2=2160 lbs landing on the center of the 9' span front and rear beam.
It is a beam with a concentrated load at midspan, this is the calc;
https://forestryforum.com/members/donp/beamclc_ctrpointload.htm
Use the #2 design values from the calc above and a 6x10 #2 tie works supporting the ridgebeam.

No drilling or notching the ridge at that size. I would put a bevelled cant strip on top of the ridgebeam that the rafters sit on rather than notching the rafter or ridge. Blocking between rafters over the ridge could hide a wire chase, even indirect lighting.

Don P

Try that again ::). The ridge is supporting a swath 4.5' wide x 14.5 feet of length x 30 lbs=1957.5lbs
I get a pass at 6x8 in #2 WRC

Tie load is (4.5'x16' x 30psf)/2= 1080 lbs
I get a pass at 6x8

The rafter plates are supporting the lower half of the rafter span plus the overhang. (2.25'+3')x 14.5' x 30psf=2284lbs
I get a pass with a 6x10

Can you tell it was a brain frying week  :D. Now double check me.

thebigrlebowski

Thank you Don!  That is great feedback.  I'll be bumping up the ridge to a 6x10 I think.  Would this allow for routing out a fan junction box and conduit ran through from the top to the box?  I'm having trouble picturing what you mean by a cant strip on top of the ridge beam.  I'm open to other options or ideas.  The image below is how I was considering doing it. This would notch the rafter a bit and allow the conduit to run on top center of the beam.

 

Don P

No, that will tend to split from the inside corner of the notch. You are limited to 1/4 depth on the tension edge (bottom). The 1/4 depth would be an imaginary line drawn parallel with the bottom edge, no part of the notch can intrude above that. So a minimal notch but, that sharp cornered notch still concentrates splitting stress.

 Notching the ridgebeam weakens it. As the notch extends below the neutral axis the tenon or housing puts the fibers under it in tension perpendicular to grain. With drop in notches or housings the effective width of the timber becomes the thickness of the remaining wood after notching.

I'm just pointing out that there is good reason not to damage those timbers. I probably wouldn't notch either if possible, set the rafters on top of the ridgebeam. Rather than notching those structural members saw a double bevelled cap to set on the top edge of the ridgebeam, bevelled at the roof angle to fully support the ends of the rafters. Timber screw the rafters to the ridge even if they are forked or lapped, metal strap over the top connecting the rafter couple together over the ridge would give an inspector rated connections.

Jim_Rogers

Like this:




But at your roof slope angle.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

thebigrlebowski

To screw that to the ridge beam, would you use something like 8 inch timber screws from above or toe screw it in from the sides?  I would think from the side would be sufficient. 

Jim_Rogers

Normally we do it from the top down so that the screw head doesn't show.
And we usually drill a pilot hole.
You'll need a minimum of 2" of threads into the ridge beam for proper strength.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jeff

Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

thebigrlebowski

Are there any advantages or disadvantages to having the rafters above the ridge beam as opposed to mounting to the side?  I saw on another site where they were above but offset. This allowed them to overlap each other at the top.  I imagine this prevents having to use strapping.

Don P

Stacking is more efficient and stronger than hanging from the side, the price is height, the beam is dropped.

Offset and nailed together does provide the tie at the top. I make what is called a cant strip that fills the triangular void on the top of Jims ridgebeam. Then I don't notch the rafters they sit on the angled cant strip, unmolested by a tension side notch. As long as the rafter couple is well married together at the ridge, any fastener from rafter to ridge is for uplift, just a withdrawal anchor. It isn't needing to hold the rafter top in shear from drifting, the couple is hanging, connected, from the ridge.

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