Can I add dormers with this foundation?

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sweetrvr

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My goal is to add 2 dormers out of the attic for livable space (master bed/bath) approx 325 sq feet total , with the dormers adding maybe 100 sq feet.

House was built in 1905, stacked sandstone foundation, limited crawlspace (but does have HVAC under the floors, so someone got under there).

Currently no obvious foundation issues, no sagging or tilt.

House is Aprox 1100 sq feet, 1 story.

Obviously too many variable to get specific without a structural engineer...but wondering what opinions the foundation experts can offer. Are there any solutions? Rough estimates?

Thanks in advance!

Current situation: joists sitting on stacked sandstone

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Here's the house. Small gabled dormer would be added facing the camera

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I am impressed, some people ask about what colour to paint it when done. You are starting at the right point.
If you are going to get a permit, if the permit dept. cares at all they should ask you to get an engineers report. So that is where I would start.
 
Thanks Neal. Yeah, I'll be pulling a permit for sure, just trying to gather as much info as possible.
 
sweetrvr said:
Thanks Neal. Yeah, I'll be pulling a permit for sure, just trying to gather as much info as possible.
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As you are in an area where you will find an engineer that is familiar with the load that can be taken by the foundation and the dirt below it.

Right now the dead weight and any loads from snow or wind are evenly spread over the foundation on both sides. You will be adding a little more dead weight but you change snow or wind loads as well as adding live loads to the mix.

Underpinning the foundation in four places may give you second thoughts on the project. So getting that good or bad news up front would be your best bet.

All you could get here is well meaning opinions that aren't worth snot when things start to fail.
 
Are you adding both dormers to the left hip above the entry, or another on the left side, or are you actually creating a 2nd story in the existing attic, and the dormer will be the light and ventilation?
 
Probably the first scenario you're describing, just two dormers, definitely not another 2nd story
 
Thanks;

I'm confused;"My goal is to add 2 dormers out of the attic for livable space (master bed/bath) approx 325 sq feet total , with the dormers adding maybe 100 sq feet."

Creating an architecturally conforming dormer for the purpose of allowing light into a space, with an existing ceiling, should not affect the foundation.
 
Snoonyb said:
Thanks;

I'm confused;"My goal is to add 2 dormers out of the attic for livable space (master bed/bath) approx 325 sq feet total , with the dormers adding maybe 100 sq feet."

Creating an architecturally conforming dormer for the purpose of allowing light into a space, with an existing ceiling, should not affect the foundation.
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Well....we're talking dormers that wouldn't just add light but livable space. This adds weight to the overall structure, plus all the other finishes. So a 110 year old stacked sandstone foundation might not work.
 
sweetrvr said:
Great link, thanks!

No real mention of foundation issues in a 105 yr old house, I'm taking that as a positive
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Didn't see your second set of photos before.
Besides the foundation, that is a complicated roof system, do you have a good understanding of how you would deal with that?
 
nealtw said:
Didn't see your second set of photos before.
Besides the foundation, that is a complicated roof system, do you have a good understanding of how you would deal with that?
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Yeah, that's the second issue. But I think it's doable. I'm not a truss expert but I think all that would need to do is move the diagonal brace (web post-?) into a different configuration.

A couple buddies that have done this before have indicated the truss is less of an issue that the foundation....but you're right, it could be an issue.
 
So it look like the house comes out on the right in the picture and the left side is back a few feet with a porch in front of it..
If that is the case, it gets a lot easier with just changing the fronts to gables on top of the original walls and fill in the missing rafters, no worry's about the foundation.
So on the front right you would remove the skirt and build a new would look like the one there now but above the wall.
On the left you would cut the rafters in the sloped area and build a new gable over the wall at the back of the porch.
All you would be doing is bringing both gables forward.
 
nealtw said:
So it look like the house comes out on the right in the picture and the left side is back a few feet with a porch in front of it..
If that is the case, it gets a lot easier with just changing the fronts to gables on top of the original walls and fill in the missing rafters, no worry's about the foundation.
So on the front right you would remove the skirt and build a new would look like the one there now but above the wall.
On the left you would cut the rafters in the sloped area and build a new gable over the wall at the back of the porch.
All you would be doing is bringing both gables forward.
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Thats exactly what I'm thinking. It will all come down to what the engineers say, but I've got some good info here to get started.

The crux will be finding a way to add stairs to access the space. But that's another topic!
 
sweetrvr said:
Thats exactly what I'm thinking. It will all come down to what the engineers say, but I've got some good info here to get started.

The crux will be finding a way to add stairs to access the space. But that's another topic!
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If that is the plan then no there should be no problem with the foundation.
Then you are looking at floor joists for what ever span you have and making the rafters deeper for insulation and venting.
Do you have a center wall front to back that has a foundation. If you do the stairs get easier.
 
sweetrvr said:
Yeah, that's the second issue. But I think it's doable. I'm not a truss expert but I think all that would need to do is move the diagonal brace (web post-?) into a different configuration.

A couple buddies that have done this before have indicated the truss is less of an issue that the foundation....but you're right, it could be an issue.
Click to expand...

This would be all hand framed rafters, the only truss you could use would be the gables and they come bear bones and you have to fill them anyway so you may as well cut all rafters.
 
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