Elevated addition

[Tree-dweller]

Quote:

Originally Posted by NW-Bound A room addition that is on posts and sticks out from the house is basically a cube with 5 of its 6 sides exposed to weather. It will gain more heat than the rest of the house in the summer, and is colder in the winter. Good insulation and adequate duct work will be needed to make it comfortable. I know, because I have been there.

Did you get the good insulation and adequate ductwork, and did it work, or did you wind up thinking it was a mistake to build it in the first place?

[target2019]

I'd think about over-engineering something like this. Being on a hill, I'd be worried about wind storms and the effects of water erosion on this structure. When an entire house sits on foundation, and a major portion sticks out, on stilts, that concerns me. What about home insurance? How much will it change?

[Koolau]

Quote:

Originally Posted by target2019 I'd think about over-engineering something like this. Being on a hill, I'd be worried about wind storms and the effects of water erosion on this structure. When an entire house sits on foundation, and a major portion sticks out, on stilts, that concerns me. What about home insurance? How much will it change?

As mentioned, we here have many, many such dwellings. Cold is not an issue, but heat and sun load certainly are. We don't do a lot of insulation - we usually just AC the heck out of everything OR have 3-side ventilation. Wind IS an issue. We do occasionally have hurricanes but more often have just plain high winds (40 to 50 mph isn't particularly uncommon.) I don't recall any issues of such dwellings "blowing over." We have lots of rain (at least on the windward side - and this year on the leeward side.) We do have some erosion problems from time to time, but again, don't recall too many houses going down because of it. We have much more problems with rocks breaking loose and crashing into someone's bedroom!

But target2019 made me think of something. If your insurance company is happy, you should probably be happy! Just a thought because YMMV.

[Bamaman]

Quote:

Originally Posted by enginerd I am also amazed all the time at stuff that licensed architects and licensed engineers can completely overlook.

I have a cousin and two close friends that are architects. I always said students should be required to work two years in the construction trades before they were allowed to start their architecture program.

[target2019]

Quote:

Originally Posted by Koolau As mentioned, we here have many, many such dwellings. Cold is not an issue, but heat and sun load certainly are. We don't do a lot of insulation - we usually just AC the heck out of everything OR have 3-side ventilation. Wind IS an issue. We do occasionally have hurricanes but more often have just plain high winds (40 to 50 mph isn't particularly uncommon.) I don't recall any issues of such dwellings "blowing over." We have lots of rain (at least on the windward side - and this year on the leeward side.) We do have some erosion problems from time to time, but again, don't recall too many houses going down because of it. We have much more problems with rocks breaking loose and crashing into someone's bedroom! But target2019 made me think of something. If your insurance company is happy, you should probably be happy! Just a thought because YMMV.

Now that you mention 40-50 mph winds being common, sorta, I picture these homes around you as box kites with sturdy tails.
🙋

Do these architects take into account the direction that big winds may prevail from?

Probably makes a difference if you're surrounded by trees or perhaps other structures nearby.

[enginerd]

Quote:

Originally Posted by Tree-dweller Thanks all. Oh yeah, we are making sure contractor pulls all required permits. "Bigfoot" footings are to be below the frostline (min 4 ft), and the insulation in ceiling, floor and walls meets or exceeds the EnergyStar guidelines for my zone. That business Enginerd mentioned about uplift in strong winds, well that's one I'll have to ask about for sure! Might have to box in underneath.

If you go to the Bigfoot website, they have some test data for uplift. So, depending on the number of posts and the sizes, the design might be ok, or it could be a simple change such as an extra post or a larger Bigfoot.

[meierlde]

Quote:

Originally Posted by Tree-dweller Thanks all. Oh yeah, we are making sure contractor pulls all required permits. "Bigfoot" footings are to be below the frostline (min 4 ft), and the insulation in ceiling, floor and walls meets or exceeds the EnergyStar guidelines for my zone. That business Enginerd mentioned about uplift in strong winds, well that's one I'll have to ask about for sure! Might have to box in underneath.

In addition boxing in the underarea would increase the temp under the room at least a little bit, as it would be then more like a crawl space, thus making the heating requirements for the room above a bit less (at least no wind to take heat away from the outside of the insulation, unless you were planning to put sheathing on the bottom of the joists after insulating.

[NW-Bound]

Quote:

Originally Posted by Tree-dweller Did you get the good insulation and adequate ductwork, and did it work, or did you wind up thinking it was a mistake to build it in the first place?

The insulation of the room addition is better than that of the existing structure. Else, the temperature swing would be a lot worse. The central heat pump is a 5-ton unit, and should be able to handle the 400-sq.ft. addition. The problem is the airflow to the area is too weak due to its distance from the air handler.

For expedience, we solve the problem with a supplemental portable electric heater when needed. Thought to myself that the airflow could be enhanced with a inline duct blower, but I still have not added it after 25 years.

By the way, the contractor used engineered I-joists rather than the typical 2x12 joists (the addition is 14' x 28'). See photo. The floor feels solid, and superior to that of the existing structure. The joists span the 14' width. One 28' side is supported by the existing wall. The other 28' side is supported by a long laminated beam resting on 3 posts. The posts are resting on concrete footings built to the local code. The walls are built with 2x6. The roof is tiled to match the existing structure.

I have not had any structural problem after 25 years.

[Tree-dweller]

Quote:

Originally Posted by NW-Bound The insulation of the room addition is better than that of the existing structure. Else, the temperature swing would be a lot worse. The central heat pump is a 5-ton unit, and should be able to handle the 400-sq.ft. addition. The problem is the airflow to the area is too weak due to its distance from the air handler. For expedience, we solve the problem with a supplemental portable electric heater when needed. Thought to myself that the airflow could be enhanced with a inline duct blower, but I still have not added it after 25 years. By the way, the contractor used engineered I-joists rather than the typical 2x12 joists (the addition is 14' x 28'). See photo. The floor feels solid, and superior to that of the existing structure. The joists span the 14' width. One 28' side is supported by the existing wall. The other 28' side is supported by a long laminated beam resting on 3 posts. The posts are resting on concrete footings built to the local code. The walls are built with 2x6. The roof is tiled to match the existing structure. I have not had any structural problem after 25 years.

Good info. Thanks