What can be done with a crawl space on an old house?

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Rob_Red

Feeling the Heat
Feb 2, 2021
384
Southern New England
Hey all I was running our air conditioning during a recent heatwave and I noticed quite a bit of my cool air is ending up in my crawl space. I live in a part of new England where the soil is full of boulders and ledge rock (people blast when making basements) and the house was originally built in the late 1800's then added onto a couple of times over the years. So part of the house is sitting on a very shallow hand dug basement with semi exposed walls made of stone and mortar. Then the additions were built on a combination of existing boulders and cement footings. this part is what I would consider "crawl space" however there is not really enough space to crawl the house is almost sitting on the ground. There is maybe 1 ft of clearance in some spots and some floor joists are supported by a VW bug sized boulder .

The space is a little damp (nothing crazy) and obviously non conditioned, however the insulation between it and the floor is very much lacking. Is there anything that could be practically done? I don't think there is enough room to encapsulate. Can I pump it full of closed cell foam or something else? I would rather not pull up the entire down stairs floor trying to make it better.

Also to keep the humidity and mustiness down should I setup some sort of ventilation? We currently have a dehumidifier down their that's plumbed in but I feel like thats more of a feel good placebo than anything else

I think the only full out fix is to lift the house and put it on piers !!! ;lol but maybe there is something I don't know about?
 
Given the poor access you describe, not much, There are firms that seal up crawl spaces by laying sheets of rubberlike material on the ground underneath and sealing the seams as needed to form an air and moisture tight barrier but they need space to work and its sounds like you do not have the space. The tough part is that in order to keep the floor from rotting you need air flow through the space.
 
It sounds like I have the same problem as you but mine is real dry because of the dryness here but I often wonder "what could I do with this? The original part to my house is 23x23 and it has a 1/4 part that is full basement height right under the kitchen where my boiler and hot water and electrical box is with a concrete floor with a vent on the floor..Its about 10x8 and has a high ceiling of about 9 feet (taking a guess here) and it is surrounded by massive concrete blocks that only go up so high and just make a ledge surrounding this area and on the level with this ledge the other three rooms to the original house is filled in with dirt and rocks then there is about four feet and the bottom of the house has the copper piping that goes to the hot water radiation things in the floor that heats the house upstairs and none of this is insulated so I wonder how those hot pipes heat up in the winter time in order to heat the house and they do but I cannot get it over a temperature of about 78 degrees so on those days I use electric heaters to supplement..but I often wondered what can I do with this space? The only thing that I thought about was maybe digging outside the front area of the house down to the level and scooping all the dirt out of it and making some more basement like the area under the kitchen that has full height.. Then I thought about "could I insulate the area some how or insulate the copper piping somehow so that I could get more heat? But I am getting tired now but have wondered through the years what exactly could I do with this? I have air flow but not enough of heat in the wintertime because my basement is not insulated.. Would I just lay insulation on top of the dirt or pump it in or what and maybe someday I will start another thread about this heating problem but just wanted you to know that I wondered about the say problem in a different way...For you could there be fans that would give you air flow and do not they have some kind of attic fans or something that might be good to check out? clancey
 
Our old farmhouse was in a similar situation. It had a hodgepodge of supports and fixes over the years, but the patio side was sitting on a big doug fir 10x10 on dirt which was rotting. There were parts where the crawlspace was only about 12" deep. At one point I had hired an insulation company to come in and insulate the floor, but the workers were down there for about 15 minutes and then came up and said, no way José. Ugh. The main difference from your situation is that is not sitting on rock.

The solution was raising the house up about 3' and putting a proper foundation on it. It was a lot of work and expensive, but looking back 15 yrs ago, I'm very glad I did it. For one, it completely eliminated rodent problems we were having in the house. After it was done I insulated the crawlspace/basement interior walls. This made a big difference in floor warmth and comfort. It rarely gets below 60º down there even in a cold winter.

House_raising-020web.jpg
 
I cannot get it over a temperature of about 78 degrees so on those days I use electric heaters to supplement..
Clancey
You must like it hot. We keep this old farmhouse at 70
and find that too warm in the winter and not cool enough
in the summer
 
I like to be warm especially in the coldest part of the winter...I hate to be cold...lol lol clancey That's a pretty house begreen is that your old rickety self out there-lol clancey
 
Cold air from AC will almost always seep into crawl spaces, no matter how much insulation u have. There are too many cracks. And for good reason. A house needs to breathe. The last thing u wanna do is completely seal it up. AC is what has caused the quandary of issues regarding crawl space dampness. In the summer, cool air from above mixes with the humid air coming in from outside, and it creates a mess. There are some things u can do to mitigate it…

1. Encapsulation- my personal opinion- it’s a scam. I’ve seen PLENTY of crawl spaces that are”completely encapsulated” that have six inches of water in them. And again, house needs to breathe

2. Lay down some 6 mil plastic vapor barrier on the dirt. You would be amazed how much moisture comes up from the ground. It’s labor intensive, but very easy. And not that expensive

3. Put in a sump pump- find the lowest spot and install a high quality pump, that pumps it far from ur house. Plenty of videos online.

i know this post was about temp, but these simple things will make a huge diff in moisture in ur crawl space. There’s absolutely no way to completely eliminate it. It’s a fact of life. But controlling it can help tremendously.
 
Thanks for the input all of those suggestions make a ton of sense. I agree that encapsulation seems scamy. What makes me scratch my head is why aren't people just trying to keep the water off the foundation?

I was thinking one way to control the moisture is to put in a robust french drain around the uphill side of the house. I would like to dig down and put in a moisture barrier along with corrugated pipe to rout the water around the foundation. Would this work? Or would I loose a fight with mother earth?
 
Along with laying down that vapor barrier your original idea of spray foaming the floor will make a huge difference. It will keep the floors and pipes warmer and keep any moisture from coming up into the house.. Also installing a vent on all 4 sides of the crawl space will help with air circulation in the summer and dry things out then close em up for the winter to keep the natural ground heat.
 
Thanks for the input all of those suggestions make a ton of sense. I agree that encapsulation seems scamy. What makes me scratch my head is why aren't people just trying to keep the water off the foundation?

I was thinking one way to control the moisture is to put in a robust french drain around the uphill side of the house. I would like to dig down and put in a moisture barrier along with corrugated pipe to rout the water around the foundation. Would this work? Or would I loose a fight with mother earth?
U certainly could do that. The better thing to do would be to dig a trench down to the footer all the way around the foundation. Lay a small bed of stone, then lay pipe with three holes, holes down, on the stone. Then cover the pipe with gravel. Make sure it all drains into the installed sump pump. Again, plenty of videos online showing how to do this. It’s basically creating a perimeter drain around ur house. It works very well. Labor intensive tho.
 
I'm in the same boat as you. 1850s house, dirt crawlspace, no room to crawl around underneath.

A little ventilation is worse than no ventilation. Warm, moisture laden outside air comes in and condenses on all the cool ground and rocks underneath leading to 100% humidity during summer. To avoid this you need either

a) enough ventilation to raise the crawlspace temperature above summer dewpoint temps (e.g. 72F). This means running fan 24/7 with a thoughtfully designed airflow pattern, at a minimum.
b) totally enclosed with a dehumidifier running.

The problem with (a) is that unless your floors are super insulated, you will lose a ton of heat in the winter and a ton of cool in the summer because it's equivalent to having an uninsulated wall or ceiling to the outside.

The problem with (b) is that it's impossible to do completely. In my house, I have been aiming for option (b) but there are still some places I cannot access to put a vapor barrier or seal up air leaks. Sealing gaps in the foundation from the outside along with a dehumidifier and a french drain seems to be a good place to start. I bought a Santa Fe Compact 70 dehumidifier and it does the heavy lifting to keep the humidity down around 75% in my crawlspace. Cost me $1200 up front and about $25 a month to run. Adding vapor barriers would probably reduce my operating costs, but so far I have not figured out how to do it everywhere.
 
thanks for the feedback @gthomas785

This is why I was wondering about the sprayfoam option. The part of the house with the non accessible crawl space has no plumbing or wiring under the floor. So what if I just pumped those areas full of foam?

My worry would be trapping moisture where I dont want it causing rot and mold, which I hear is a major concern.
 
thanks for the feedback @gthomas785

This is why I was wondering about the sprayfoam option. The part of the house with the non accessible crawl space has no plumbing or wiring under the floor. So what if I just pumped those areas full of foam?

My worry would be trapping moisture where I dont want it causing rot and mold, which I hear is a major concern.
Hmm, my first thought is that sounds like a lot of foam, and expensive. How exactly would you "pump" the foam in? I assume you'd need to drill an array of holes in the floor from above and use a slower curing mix than what is typically used for spray application.

If you had a way to verify complete coverage of the subfloor and framing, then you wouldn't have to worry about moisture trapping. But if there are any channels or voids in the foam then that would absolutely be a problem.
 
I feel like I'm drifting into hypothetical talk now but I think to do it right the floor would need access holes created, and I can get a good view of the entire area but there is only about 12 inches of space between the ground and the floor joists. So I would think some sort of wand could be used to spray in there.

Seems like the only sure fire way to make it perfect is lifting the whole house and installing a proper basement
 
Well it's hypothetical for me too but I have also envisioned attaching a foam gun to the end of a long stick with a string around the trigger and using it to spray the back wall of my foundation from 20 feet away. No reason it can't be done, except everything -- like being able to actually point it in the right direction, see what you're doing, etc. :cool:

Your house is 150 years old. Don't strive for perfect, just strive for better than what you already have!
 
Building techniques vary around the country and climate. In my area the choice is ventilate the crawl space to the outdoor air conditions or seal it up tight like a drum from the ground. There is plenty of moisture in the ground so dehumidifcation really does not work unless there is a vapor barrier. Dewpoint issues will cause dampness and eventually mold. I have seen my share of the results of rot and moldy spaces. The tough part is there is no cheap fix. If the structure is worth saving, the choices are expensive, many folks just put a for sale sign and sell it for cheap. I know folks who have hand dug a crawl space under a building and years ago I helped dig a basement opening under a large porch 15 by 20. We knocked it out in about 8 hours using a dirt converyor and shoveling by hand (marine clay). Unless labor is free is its usually not practical. Heck I knew one person who hand dug their basement down 2' . He shoveled it into wheelbarrel and hauled it up to the outdoors in 5 gallon buckets. I think it took him most of the winter. If the structure is worth saving and is not already to far rotten then the best option is have the house lifted on a new foundation. The tough part is usually the floor structure is already so far gone that the house has to be lifted up from the walls .

Rocks can be broken up with "slow dynamite" the rock gets drilled with a rock drill and then a grout like product mixed up and poured in the hole. Come back in 12 to 24 hours and the rock is split. It works great on rock and un-reinforced concrete.
 
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We have a vapor barrier and new gutters all around to carry the rainwater away from the house. The crawlspace stays bone dry now. After 15 yrs of being sealed and enclosed there is no moisture issue in spite of being in the "rainy" northwest.
 
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Yea I would think that a wand of some kind of spray could be used like you think so maybe we both thinking "in a hypothetical way" in order to try to solve the problem..I have the same problem but it has a different outcome to where my heat will not get over 78 degrees yea its hot sounding in temperature but there is a five degree difference that has to be before it will even kick on and this is a problem for me--don't really know why my boiler works like that and its a peerless one..Never did understand it...This is just a hypothetical suggestion--would piped heat under that floor keep it dry with insulation maybe--crazy I know--but when I switched to piped heat my basement got warmer and dryer as well---so I am heating the basement too--lol Oh Brother...(I have problems)..lol I am old and tired and my house is old and tired (1926) and down the road I am sure all these houses will be bull dozed so right not I cannot see "lifting" my house to fix this the problem but that I guess would be the right way but so expensive and for me more expensive then the house is "worth".. and I would rather move the house then that so I think I am stuck with this problem and its cheaper to be stuck with it for now..clancey
 
I do have radiant (piped) heat in my floor. The problem I have is some of the heat goes into the crawl space which is drafty. This is due to mediocre insulation in the floor. It’s mediocre because the access is limited.

the prior owner installed the system I assume when the floor was done and let’s just say I would have done it a little nicer
 
This is a serious problem and it is sad that the previous owner set it up like that and for me too why in the world would they have a fourth of a basement and not the rest--terrible and money wasting as well as the possibility of dampness and termites too...Feel bad for you and feel bad for myself and when I bought my house did not know anything about anything and still do not know much...lol clancey
 
yes it’s a problem and unfortunately it’s not rare around my part of Connecticut. Like I said earlier our soil is 90% boulders. If I were around in 1890 I wouldn’t be hand digging any basement either.
 
So here is some temp and RH data from my crawl space. By southern standards it in pretty good shape. But what I’m seeing is enough to concern me. I’m using a 15$ GoVee wireless temp and humidity sensor.
You might ask why does the RH drop every night at midnight? My leaky ductwork. By midnight the programmable ac has lowered the temp by a degree or two and isn’t running as often couple that with increasing RH outdoors. Now I have considered closing the vents off and adding a room dehumidifier. Thinking it would run 12 hours a day at .5 kw or so that’s 25$ a month for the summer. Seems like a cheap enough option. I’d add a vapor barrier. Logging the the temp and humidity can be helpful.
Evan
 

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