Hello-
Building a screened porch that’s not directly attached to my house. Currently the trusses are up, and putting on the roofing this weekend. Problem is when you push on the top wall it sways a bit.
What common methods are there to address this? Obviously, since the screened openings are in full view I can’t just throw some diagonal bracing up. Also, I want to avoid closing in the area below the railing. Would some corner anchors from Simpson put on each of the corner posts (attaching the post to the base) help?
TIA,
Kevin
Replies
When you push which way? The length of the wall or across/perpendicular to it? I can assume down the length.
Doesn't it get windy there? Did you get a permit? The BO would have likely given you some requirements that would have eliminated this. I'm not berrating you ... BO can frequently be your friend in solving/preventing problems.
I think you may have two issues: Connection of the columns at the base ... you imply they aren't really connected, just sitting there? You need to anchor yourself down for sure (through to the ground).
Also you have a wall shear problem because you have no moment resisting connection of the columns/cross members for the roof. Simpson may have a relatively heavy flat 'T' piece to place on the column and then reach out across both sides of your beam. If they don't, you can always go to your local steel fabricator and have some made. How many you need depends on the height and the size of your roof and how much force is placed on it (are you in hurricane country? You need to have the same consideration for the end walls as well.
Don't discount being able to use thin cables in cross pattern ... I know you don't want it, but thin cables may not be that obtrussive and at a glance, many wouldn't even notice.
Not sure if you may need to consider shear forces at the bottom of the column as well ... maybe a good structural building/engineer can give you some hints there.
When I lived in Australia for a bit I noticed that in some new houses they put in rather thick cables and big turnbuckles within the roof. Very strange to see. They told me what it was for but for the life of me I can't remember but I'm sure it is for the same reason you are suggesting.roger
If the roof is not sheathed w/ shear resistant sheathing (e.g. 'skip' sheathing), then some kind of diagonal bracing may be in order ... one method is the cable and turnbuckle to prevent racking of the structure.
That's a good point. I wonder what they do up here on the west coast when they use cedar shingles. They don't use any sheathing but rather strap the roof. I'll have to take a better look and see how they prevent racking or maybe all that strapping is all that's needed.roger
Sometimes diagnoal wood bracing attached to the underside of the rafter/truss cord. Possibly diagonal bracing at the center point of the roof ... but that would stress ext end walls in a wierd way unless you have some other diaphram to distribute the loading.
Either cables criss-crossing three of the window walls or knee braces all around.
If the roof won't be sheathed with sheet goods then you need a diagonal brace across the bottom of the trusses.
Also, if this porch is elevated very much (and you don't have diagonal flooring) you should run a diagonal brace across the bottom of the floor joists.
Just to clarify.... the roof is going to be 2x6 T&G. Using 16' lengths that run the full length of the roof. Maybe I'm worried too soon, and that things will firm up once I add the T&G. Ditto for when I add the railing.BTW, using 2x6 because this is an open rafter plan where the rafters are spaced ~4' apart. Similar to this approach/style:http://www.rd.com/familyhandyman/content/50683/
Edited 5/30/2008 11:54 am ET by kevreh