Building our retirement home

[KiotiKowboy]

Wellllllllll ... It's like this

The truss designer was shown drawings that included a cross beam. He said, without the beam, he was not comfortable for the long haul.

As a result, we decided to beef up the ground support. The steel posts are 8" square tube steel with 5/16" walls. They are planted in 5 feet of concrete and have 24 6" fingers extending from the 4 sides below ground level. Additionally, when we pour the decks, there will be another 2 feet of fill and 4" of concrete.

We have a "similar" design on our current home - but - it has a 3rd post in the center of the roof. After 7 or 8 years, minor cracking was starting in the mortar joints of the stone on the 2 outside posts. At that point, a cable was installed between the beams and all movement stopped. This was all a very slow progression .... yes, time and gravity.

My thoughts are to go forward with what we've done and watch closely for signs of trouble. It may take years ... or not ...

 

[tbrooks26]

My thoughts are to go forward with what we've done and watch closely for signs of trouble. It may take years ... or not ...

Sounds almost like "Hey yall watch this". My local small town lumber yard has an in-store engineer. I'm going to get up with him about a couple issues with my project. Mainly shed roof connection to a truss gable wall, and removing support from under another gable wall truss. Both simple things that I could probably easily overkill with some extra bracing, but I'd rather be safe then sorry. Because I ordered my trusses through them, he will come out free of charge!

 

[KiotiKowboy]

Sounds almost like "Hey yall watch this".

LOL - I get your point. Still, there is no way in blazes the thing is just going to come down.

 

[tbrooks26]

I could make a Titantic reference there lol. I have to say those post should make it pretty solid. If it does start to show problems, that means your connections are already weakened, therefore new stronger measures will have to be taken than what would have to be done now. Either way it seems to me you are putting a good amount of time, heart, and money into this home. Why take a risk? I'd call an engineer. Maybe he'll just recommend plywood as I did. I have to say if it does fail it will probably fail slowly. I have seen it happen with post and beam work. We will soon be rebuilding a 16x24 post and beam carport roof. It's still standing, probably would last quite a few more years, but the collar ties were not properly attached. It has spread 3-4". We will be looking at days of building temporary supports and bracing in order to fix it properly. We're actually gonna use an engineer to help with a repair plan. There's like 15 of these carports in this complex, job security lol.

 

[EddieWalker]

A center post would solve a lot of it, but then they are not really trusses anymore. And who wants another post after paying for trusses to avoid that?

I can certainly understand your plan to hope for the best and deal with it if it ever becomes an issue. From what you have done to address the what if's, I think you have a better then 50-50 chance of success. The real question is if it happens, how quickly will you notice it? how much additional damage will be done by the movement, such as movement in the decking, shingles and the posts?

Adding a cable, or whatever you prefer, to keep the roof together would be a very cheap, simple thing to do at this stage of everything. I've found that the older I get, the less I want to go back and fix things. Nothing worse thing fixing things in the rain, and when it fails, it will be during a storm.

 

[KiotiKowboy]

Adding a cable, or whatever you prefer, to keep the roof together would be a very cheap, simple thing to do at this stage of everything. I've found that the older I get, the less I want to go back and fix things. Nothing worse thing fixing things in the rain, and when it fails, it will be during a storm.

I was thinking a bit earlier that I'd hate to see the first snow bring it all down

Just for grins ... Is it possible to buy something ready-made for a specific length. Our span is about 28' to the outside of the beams. And, of course, it needs to be adjustable for tension.

 

[TomSeller]

Maybe put up some cables and leave them slightly loose as a safety net for the first few years or until you have a good snow load or high winds. If they stay slack you'd be good to go. If they tighten up, you have time to figure out a permanent fix.

 

[GPintheMitten]

I suggested several days back to use stainless steel cable and turnbuckles as used in the sailing industry but the issue was birds would rest on them and poo on the porch.

It might be fine as constructed but spread could happen. During middle ages, the Cathedral builders figured out that despite the advanced design of Gothic arch, they needed flying buttress to offset spreading forces (which are really gravitational forces).

So maybe you should at least put up some reinforcement now to which you could later attach cables and turnbuckles. Then monitor movement if any. Probably a small movement like 1/2 inch or less between the posts would indicate the need to reinforce.

 

[TomSeller]

I suggested several days back to use stainless steel cable and turnbuckles as used in the sailing industry but the issue was birds would rest on them and poo on the porch..

IC... I must have missed that post. Myself, I'd rather deal with possible poo for a few years than a possible collapse. Just my $0.01

 

[CurlyDave]

I was thinking a bit earlier that I'd hate to see the first snow bring it all down

Just for grins ... Is it possible to buy something ready-made for a specific length. Our span is about 28' to the outside of the beams. And, of course, it needs to be adjustable for tension.

I would think along the lines of a metal rod, say 3/4" or 1" in diameter. If you wanted to put one between the steel posts, you could have 6" or so of each end threaded and drill holes through the posts. Nuts and washers on each end and you have an excellent tension member. Tightening the nuts will tension the rod, and of course you can adjust tension either with a torque wrench, or just by feel (what is sometimes called an "Armstrong torque wrench").

Personally, I think a slack cable is going to destroy the aesthetics of the structure even more than a proper collar tie, but a solid rod would certainly sag less than a cable.

* * * * * * *

Now there is an alternative to tieing the posts together at the top.

Looking at the pictures in post 248, it appears that there will be a deck at the height of the house floor under this roof. A very strong tension member connecting the two posts at the height of the floor will substantially change the interaction of the post footings with respect to the earth.

Either a tension rod, as described above, or a steel beam welded between the posts will greatly reduce the side forces the footers have to withstand. Also, the cantilevered portion of the posts will be shortened reducing the deflection at the top of the posts.

Best of all, the beam or the tension rod can be hidden just under the surface of the deck.

No this isn't the way to design it in the first place, but given what you already have it may be a good way to increase long-term properties at a reasonable cost.

Consult an engineer first.

Think of a tension rod where the red line is in the picture.