Couple more questions about connecting an addition..

[Ernest T. Bass]

Here's part two of my thought process..

I did some searching but didn't find many threads on addition construction; at least not that pertained to me. Kinda surprising--maybe I'm blind and not finding 'em, or maybe the answers are just obvious. Anyhow...

What's the best way to connect the addition wall framing to the existing house? Obviously you cut the sheathing back on the house and add a stud or two to make a standard corner, but do you cut the house's top plate out so that the addition's top plate can lap the existing one? Could you just add metal strapping to the corner instead?

Also, the addition in question will have a pier foundation, and the existing house is on a block basement. Due to the addition's roof being perpendicular to the existing roof, the main girders under the floor will be also be perpendicular to the existing foundation. Specifically, the ends of the girders will need to be connected to the block at a right angle. To reduce the amount of piers needed, (and also because their are some underground obstructions), it would be nice if the block foundation could hold one end of the girders so we don't have to put piers right up against the house. What would be the best way to connect the ends of the girders to the block? Cut a notch in the block and set the girder in, use a heavy bracket with wedge anchors, etc?

Once again, I hope this is clear and I can't thank you guys enough!

[glenn kangiser]

I think what you have described are all sound building practices, Andrew.  If the block is not grouted solid I would suggest grouting it solid under it and use a roofing shingle under the girder to stop moisture.

Others may have more ideas.

[Ernest T. Bass]

Grouted solid means filled with concrete? So just chop a hole and fill'er up?

[glenn kangiser]

I'd bust out the opening you want and fill 'er down -- maybe a way to put in anchors too.

[Ernest T. Bass]

Sounds solid to me, if the foundation is up to the added weight I guess..

[glenn kangiser]

If you have any concerns about that where the end joins, you could just pour a concrete pier to take the added weight at the end joining the wall - maybe easier than breaking into the existing one anyway.

[Don_P]

I'd be tempted to go down to the original footing if possible and form a pilaster tied into the wall. If in doubt you can widen and thicken the bearing. You can use metal strap above to tie the top plates.

[PEG688]

I'd suggest cutting out the top plate and doing a proper lap UNLESS that connection is directly under a existing truss or rafter. Then I'd use a  metal strap  or a 90  deg. angle  bracket.


On the pier near the existing foundation I'd suggest a new pier dug a foot or so away from your existing foundation  and cantilever the beam ends over to the existing block. Use a approved barrier such as felt or Vycor if your beams are not treated , block is looked at as concrete by inspectors.

Cutting and filling existing block is a PITA and seldom would your cutting and filling be adequate or precise enough.

 As far a tying the two together , are you using the same size and type of floor joist? You should IMO , when you tie two building together and use dissimilar types of materails you get Odd movements as the seasons change.

A regular lumber set-up will move different than TJI or car decking on post and beams.

 Bu IF your joist are the same your "rim" that runs along the existing joist could easily be lagged one to another , or thru bolted , over kill IMO. Lags 16" OC one near the top the next near the bottom staggered is a hell for stout tie in for joists then your sub-flooring could also be cut back so the tie in could be a gusset floor to floor. I'd also recommend IF possible that any  underlayment that MIGHT be used if the two rooms have similar finished floors , be run thru the opening , say a door or passage way opening so the underlayment also does NOT break on the tie point.

 You should open up that tie in wall so you can see all layers of the old work , joist top , sub -floor thickness , and underlayment, etc , Cut out the bottom plate so you can clearly see every thing thats been done before , that may change your approach to exact heights . Also check your new stock for exact dementions before you nail down your beam heights.

Now is the time to make final adjustments   before you pour.

Write down notes and numbers , and before you decide to "change" something in mid build review those notes or better  yet storey pole the whole section , so you don't trip yourself up with a , at the time , "brilliant idea"  that throws the whole plan into a reactive instead of pro active process.


 G/L PEG

[Ernest T. Bass]

Thanks for the great advice, guys! That's just what I wanted to hear..

Like I said, there are some underground obstructions, so I'm not sure how close we can easily get to the house with a pier.. Our beam's will likely be 12'' deep, so we could cantilever at least that much. PEG, you said to use a barrier between the beam and the block, but if the house end is bearing on a pier does the beam even need to touch the block at all?

Also, as far as lag bolting the new rim to the old rim, are you figuring that this would be like a ledger? Because the new joists will be running parallel to the old house..

One other thought: What if we were to set the floor beams on TOP of the old foundation (side-lapping the old joists a bit) and use hangers to install the new joists at the same height as the old, kwim?

Thanks!

[PEG688]

Like I said, there are some underground obstructions, so I'm not sure how close we can easily get to the house with a pier.. Our beam's will likely be 12'' deep, so we could cantilever at least that much.


  Yes I'd think you could cant about 18" pretty safely , a foot would be no issue, normally . I did miss the part of underground obstructions , but in my mind the "new" pier would be a foot to 18" from the existing block wall to avoid the existing footing and not undermine the same. 


  PEG, you said to use a barrier between the beam and the block, but if the house end is bearing on a pier does the beam even need to touch the block at all?

  You could just end it a 1/2" short , BUT things tend to go together better if one think touches another. The barrier allows for that , this is especially true when working alone, you can butt stuff together and a little pressure allows you to balance things easier.   

Also, as far as lag bolting the new rim to the old rim, are you figuring that this would be like a ledger? Because the new joists will be running parallel to the old house..

  Call it what you want a rim / ledger / box sill, either way you'll have a member there at least to hold up the new floor sheathing , if the joist where 90 deg, to it you'd be placing your hangers on it , so ledger / rim / what ever you'd like it to be.   

One other thought: What if we were to set the floor beams on TOP of the old foundation (side-lapping the old joists a bit) and use hangers to install the new joists at the same height as the old, kwim?

Thanks!

  The issue there would be getting new and old stock exactly the same width , generally even three or four year old similar lumbers ,

  #1:  the older stuff is fully shrunk so it generally is 1/8 to 1/4" thinner in height / top to bottom there where most shrinking happens , not in lenght or thickness , but in width.

  #2: Hangers squeak , lots of hanger = greater potential for more squeaks , if they can be avoided it's better to do so.

#3: Hangers cost $$ so it's a win / win if they can be avoided.

   All of that is IMO. Take it for what it's worth , 30 years of experience must be worth something eh!


 

[Ernest T. Bass]

Yes, I value your opinion a great deal! As far as the cost issue of the hangers, we would be getting by with 3 less piers so that would offset.. However, for the sake of foundation stability and the other points you mentioned, sounds like we should add the extra piers if possible.

The reason I brought up the rim joist is because I don't believe we would need all those lags if it isn't functioning as a ledger, right?

Thanks again--got lots to think about.. Keeps me outa trouble

[PEG688]

The reason I brought up the rim joist is because I don't believe we would need all those lags if it isn't functioning as a ledger, right?

  Yes maybe , I'd still lag it maybe a bit less / fewer lags , but that tie together is a movement point so attaching solidly is wise.

   
  And re-reading or think about what I wrote , I could see you might think I was over the top / upset / maybe condescending , but I was just pointing out issues I've seen / heard and done , so look at my comments as facts . Just facts. This place is interesting , makes all of us think , really.

  G/L with your project , photos are aways welcomed and they help with the issues / info as well.

PEG


   

[Ernest T. Bass]

And re-reading or think about what I wrote , I could see you might think I was over the top / upset / maybe condescending ,

Actually, I wasn't detecting an edge at all, no harm done! Besides, we all know your bark is worse than your bite.

Thanks again for the info. I see your point about that rim being a movement point, especially if the new subfloor doesn't lap over the old joists.

[Ernest T. Bass]

Okay, the piers are going in tomorrow, couple more quick Q's.... Does it matter exactly where the addition walls connect to old? Can we position the new building anywhere we want and just add some studs to old wall to frame out the corner?

Also, the old joists are about 8 7/8ths, so it appears that they've settled at least a quarter.. Should we line up The new 9 1/4'' joists with the top of the old joists or the bottom? Obviously there would initially be a little ledge it the bottoms are lined up, but the finish floor will splice there (unpreferable, I know), and wont the new joists then settle down to the same level as the old?

Thanks!

[Don_P]

http://www.woodbin.com/calcs/shrinkulator.htm
generally when I've metered fresh stock from covered storage in a lumberyard it does read very close to 19%. I figured you would end up drying to around 12%. I checked the species included in the SPF group and the range of shrinkage should be from a heavy 1/16-~3/16. That was a mouthfull of assumptions there though. If the footing is not tied firmly to the existing one, will it give a little also?

The tie in can go anywhere in the wall as far as the wall is concerned, look up to see if there are any problems there.

[Ernest T. Bass]

Thanks Don. The foundation piers and beams are in.. Soon as the concrete firms up we'll start framing. I know it's not preferable, but I think we'll have to insulate the floor before sheathing it, as the crawl space is only a foot or so in some areas, due to the height of the house and the fact that we didn't want to have a dozer out to regrade the lawn.. We're still going to have staple some house wrap down there or something. Maybe we can cut it into strips and install between the joists from above?