Two story house. Upstairs bedroom has a deck (9*9). Below that is
the (bigger) first story deck. I wanted to create a screened in area
on my lower deck by framing walls up to the upper deck's rim joists.
However, this would not give me enough room so I decided to expand the
footprint by building a small, low-pitched shed roof attached to one
of the upper deck's rim joists. It's great, just enough room. But in
my haste to finish the project I didn't consider the effect of using a
single top plate for the new supporting wall.
The new wall is 2*4, 16" oc. The rafters are 2*4, 5 ft long 24" oc.
The total roof area is 50 sqft. 10' * 5'. I sheathed the roof with
I don't think that this is enough load to really cause the top plate
to sag but now I've got to thinking about it. One thing that I have
to do anyway is to install 2*4 horizontal blocking between each
rafter, resting on the top plate. The initial reason for this was to
block off mosquitoes etc.
The question is, would this blocking be enough to stiffen up the top
plate for such a small roof? Or should I also screw in some 2*4
blocking in between each stud and attach those to the top plate?
Thank you and I apologize if it's long winded. I wanted to be as
thorough as possible.
Mosquitoes aren't apt in dark and dry places. What you're describing is
bird blocking. Typically, has a hole drilled through it wire mesh screen
over the hole, Purpose is ventilation.
Don't walk on that roof, ever.
There are 2 general purposes for the double plate where joists and rafter
ride. One is supporting weight strength. Which you seem to address here.
The other, you're iginoring.
Yes, I understand that it's called bird blocking but I'm not blocking
birds, I'm blocking mosquitoes. :)
Perhaps you are picturing a completed house but this is a screened
porch wall, there's plenty of light and most definitely warmth.
As I understand it, the double top plate adds rigidity to the top of
the wall, helps weight distribution and ties intersecting walls
together. The only wall it's connected to is about 3' long, non load-
bearing and screwed like crazy to the corner post of the new wall,
edge rafter and 6*6 that's supporting the deck above. The other side
of the new wall is screwed to the corner post (2*4) of the house.
So you agree that the "bird blocking" will help distribute the weight
of the roof? Should I put blocking underneath the top plate between
each stud? I figure the bird blocking should act as a semi-
Are you friggin kidding me? What are you getting at? If you don't
understand the need to screen/block the mosquitoes out then you're
right, end replies for sure... And what are you going on about
secondary, primary functions of a double top plate? If you have an
opinion then please do share.
In coastal NC. I have used hurricane ties at the "ledger" and will be
putting them on the rafter-to-top plate. I haven't finished the wall
because I don't know if I want to pull the roof off and do it over. I
also need a couple cripple studs above the door but I want to get my
bearings first. Also, the rafters are pretty close to the studs.
Here are some pictures. I hope they work.
If it were me, I'd add a 2x4 between the studs in the locations where the
rafters are not close to in line with the studs. In other words, where the
top plate takes the most rafter load. Might not be necessary but the top
plate would be reinforced where the load is.
That's what I was thinking about doing but I wasn't sure if it would
help. It made sense to me but that doesn't mean much :) Doing that
will also give me a nailing surface for the rafter ties. I'll do it
all the way around. It should act as a weakened double plate,
correct? I say weakened because of all the connections at each stud.
If you were me would you consider pulling the roof off and re-doing
it? When I screw up something it bugs me to no end. I think pulling
the roof back off would be a waste of time for such a small load.
If I understand correctly, roofs are rated at so many pounds per square
foot, you don't have near the roof area of a house roof that would rest on a
double top plate. If you wanted to strengthen it just to be sure, you could
put the doublers between the studs and fasten doublers to studs to support
the "between the studs top plate doubler". Basically the same idea as a
door or window but without the opening. Notice how the force of the roof
load goes to the header and down to the jack studs. You shouldn't need full
length jack studs, just something to transfer the load from the "header"
between the studs to the studs themselves. I think you could make what you
have as strong as or stronger than a double top plate faster and easier than
I had figured that the load was small enough initially but , as usual,
I started to over think the issue. However, I now have a different
concern that I would like opinions on.
Where the rafter meets the side of the house I did not cut out the
cedar siding so there is a small gap caused by the angles of the cedar
lap boards. At first I didn't want to go cutting on the siding but
now I wonder if flashing it will be a problem? I thought I could just
foam and caulk the gap but now I'm worried that water could get
trapped and rot the siding. Have you ever used metal flashing on a
connection like that?
If I don't cut away the siding the flashing won't be tucked under the
siding but instead flush with the face of it and then down over the
tar paper. So I might wind up removing part of the roof anyhow. But
now that I've got some feedback on the support issue, I won't be
redoing all the rafters, just the house connection.
Also, I would use a circular saw on the siding but what about nooks
and crannies? Should I get an attachment for my drill to do that
part? What's the best way to make smaller cuts in places that a
circular saw won't fit or would make too big a cut?
Thanks for the info.
If you could keep water away from the area you could seal it, if it's going
to get wet then it would probably need to get some ventilation to evaporate.
I'm not sure what you are planning on for siding your addition but perhaps
the trim would keep rain away from the area, and you could seal it up as you
As far as cuts in nooks and crannies, try whatever looks best for the job.
A few things that come to mind might be a sawzall, jigsaw, hand saws,
Roto-Zip, Dremel tool, router. Milwaukee has a handle that holds sawzall
blades "Milwaukee 48-08-0401 Quik-Lok Job Saw" that received good ratings on
the Amazon.com website, with all the reciprocating saw blades available, it
should be handy saw to have.
The siding is going to be aluminum screening with those spline kits
from Home Depot/Lowes. When I complete the porch above, the roof for
the upper deck is going to be dumping water down to the lower so I
think I'm going to cut out the siding and flash it like a ledger
connection. Or I could leave it alone and let the gap drain but I
think I should probably just flash it. I have seen bad connections
like that rot out siding and sheathing.
first, as to your initial question, a single top plate for your
application should suffice. technically it isn't allowable on load
bearing walls for a number of reasons ranging from crushing/bending
to edge nailing for your structural sheathing. but this being
attached to your home and of such a small area i really wouldn't
worry about it that much. next, the "bird" blocking does actually
serve a purpose in increasing lateral capacity. you can think of it
as either providing a continuous path for the load from sheathing to
top plate to the wall sheathing or as a method of keeping the
rafters from rotating. so, with that said, installing the blocking
and putting nails from your roof sheathing to the blocking at say
4"o.c. would be good. from there some cualking and your mosqito
issue is solved. if you plan on putting hurricane straps on the
rafters, as you should for NC, i would recommend simpson SSP type
connectors at every second or third stud, top and bottom to get the
load all the way to the foundation. as for the siding, it would be
much easier to just screw into it, making a ledger of the last
rafter - cualking that off and putting flashing. either way,
attaching that part to your main structure is a good idea -
otherwise a good wind may send it flapping a bit against your
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