Hiring an engineer to evaluate footings
Hi! I have a house that was built at 2 different times. The first part was built in the 40’s and is a block 2 story. The second part was built sometime later, has a block basement and is a single story. The roofline on the second part is really wierd. I am wanting to rework the roofline but have ran into some snags. I have 2 options:
1. Build a new roof with an attic space.
2. Build a new roof with a bonus room instead of an attic.
Both will look the same from the outside. There is enough space to have a 12 x 20 bonus room up there after reworking the rrom so it would definitely be worth it. But the city building inspector has told me that either way I go I will have to get an engineer to evaluate the footings to see if they can support a second story. Even if I just go with an attic space there will be much more than 30 inches of headroom and he said the load would be the same as a bedroom because it would be used for storage.
My questions is…has anyone had any experience with something like this? Is it possible to get an engineer to evaluate the footings on an hourly rate? What am I looking at as far as cost(I think he will have to present stamped drawings showing that the footings will support it). If they won’t support it I guess I am really in a mess.
Thanks,
aswhitehead
Replies
Engineers do this all the time. If the footings are sitting out in the open so they can see top and sides it will be something like a $500 charge for a document the city will accept if the young kid just out of school can do the field check. If they have to have a helper dig out the footing to take a looksee it will be more expensive. If they are careful, realizing old footings are not necessarily guaranteed to be uniform all around the house, they want to see the footing all along the wall which gets expensive if they do the digging.
One old civil engineer would drive a skidsteer mounted core sample drill around the foundation, poking at the footer and directly outside it to determine roughly how wide the footer was as well as what the composition of the soil was. He was dirt cheap and probably charged half what the other guys would. Sometimes a smallish footer will still support the weight if the ground under it will hold.
We handle the situation in one of two ways, but it's almost a certainty that the old footer won't handle the second floor unless you are very lucky.
First is to design the second floor with a minimal number of point loads going down to the foundation and large square pads (4' to 5' are typical) are poured under the existing footer for those point loads.
Second is to excavate under the existing footer in 8' sections, placing concrete deck blocks and steel adjustable post bases to support the footer until the new, typically 24" x 12", footer is poured. The deck blocks are left in place and don't pose a problem. Short sections of rebar are worked in on both sides of the deck blocks, allowing for decent overlap (40x diameter).
More expensive, but sometimes desireable is to support the entire second floor with posts outside or inside the existing foundation. Some clever designs hide such posts in covered decks, closet walls, and other such areas that disrupt the interior wall finishes the least. Often these designs require large wood or steel beams. If the client is living in the first floor and doesn't mind paying 10's of thousands more to be able to do so, this can be a viable option.
I've seen engineers come up with schemes of epoxied rebar in the existing foundation and concrete poured to either side of the old footer, but it's not generally that difficult to dig under the old footer and simply pour a new wider footer, which is my prefference.
As often as not with 100 year old houses, it's simply not worth keeping the old foundation and it's torn out and replaced in sections, or the house is jacked up and whole thing is replaced.
Good building
Beer was created so carpenters wouldn't rule the world.
Thanks for the very informative reply. I will say one thing...there is NO WAY i am going to all of this trouble and just put an attic space up there.
That being said...of the 2 options you gave, will the engineer just give me the drawings of what to do and I can do the excavation/pouring new pads/etc? Or will they actually want to do that work?
At the front of my house, the basement is completely underground with a concrete patio all the way across that. I assume that the concrete patio will have to come off and all of the dirt dug out down to below the footings so the engineer can see.
This looks like it is going to be a very expensive, involved project. BUT...I have to do something as the roof lines REALLY STINK at the moment and I am fixing up this house for resale. Also, the addition of the bonus room would definitely add to the value of the home.
thanks,
aswhitehead
On rule about engineers is that they NEVER want to do any work!
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Edited 8/18/2007 4:50 pm by DanH
On rule about engineers is that they NEVER want to do any work!
yup....if they wanted to do the work they wouldn't be sitting at a desk to begin with.
the problem is...some of them should do some of the work that they are telling us to do all the time, might make them rethink a few things. View Image View Image
An engineer will certainly study your specific site issues and produce a set of dwgs and may even recommend a foundation contractor to perform the work. He will inspect the forms and reinforcing steel prior to concrete pour. The building inspector will also inspect the install to the dwgs.
Arrange a initial consultation with an engineer, he will inform you of the feasibility and the rough total cost involved, you may be pleasantly surprised.
Most engineers I know focus on engineering, we have no desire to also be contractors otherwise we would have chosen that path.
Unfortunately, there are far too many contractors/homeowners that do not understand the laws of physics and attempt to design structure themselves with disastrous results. Dont be one of them!
Point well taken. I plan to contact an engineer within the next few weeks for an initial consultation. Thanks for all of the helpful information.
aswhitehead
That being said...of the 2 options you gave, will the engineer just give me the drawings of what to do and I can do the excavation/pouring new pads/etc? Or will they actually want to do that work?
The engineer will charge something like $500 just to look at it and write what he's found on a piece of paper. Expect $500+ for an engineered design to solve the problem depending on how elaborate it is.
You'll be able to do the work yourself, but make sure the engineer knows it's you doing the work so he doesn't hand you something that requires specialized forms or whatnot.
I should also add the disclaimer that what we do successfully on a regular basis, is easy to describe, but not always easy to implement well. Supporting footings with the pads/adjustable metal post bases is something I wouldn't recommend unless you are confident in your own abilities. It's only a statement of what works for us, not what will work for anyone else.
Good building
PS Since you said this is for resale, it should be said that some engineered solutions are going to be cost probititive and you'll never get the money out of the house as an income property. I can recommend a guy if you want to lose money on an overbuilt structure.
Beer was created so carpenters wouldn't rule the world.
I would say you are just a mite cynical... Some months ago, I paid a $500 flat rate for design of an engineered 30'x40' slab for a steel frame building. Recently, I am working with an engineer to design a 20'x30' ICF building with a concrete roof. The charge is $85 an hour for the engineering and $45 for research and drafting services. So far, My experience has been much more positive than I assue yours has been and I have found the firm to be fairly conservative in its charging of hours for services.
Wow those rates represent two decades ago here. I got stuck with a $150 bill for the engineer to read bar joist charts to me, while I tried to get him to understand that anybody could read the charts. Got absolutely nothing for my money.
The other PE got the next proposal. Design for a 2 story underground reinforced concrete. He'd done 15' for me before. Scared him to think about much higher. When I suggested a successful New Zealand method that had been used near here he said he knew of the project and didn't want to know anything about it. Consultation cost $250, 5 yrs ago. Have managed to do without since.
Consider yourself fortunate with your engineer. PAHS Designer/Builder- Bury it!