outside basement insulation

keachier · 05-27-13, 10:17 AM

I plan excavating around the house to install drain and put urethane on outside concrete basement wall and cover it with mesh and concrete.Is thi a good idea.My thingking goes like this,if you can put insulation from exterior you cut cold between basement wall and floor and base of the exterior wall.

stevehull · 05-27-13, 12:19 PM

Bonjour Kiechier,

Tres bien and this is exactly what to do. I used rigid 4x8 foot closed 1 inch closed cell foam boards after spraying the walls with an elastomeric coating. Then I backfilled with sand.

A drain at the base will drain away any water.

Putting the insulation on the outside of the basement wall decreases condensation on the inside wall. In your area, the deep ground temp is about 44 F or so and with no insulation, the wall surface on the inside will be cold. Any air with a dew point above 44 will condense. The resulting environment is perfect for mold; damp, cool and dark.

The insulation on the outside concrete wall allows the inner concrete wall to stay warmer and condensation is minimized.

I have done this in several homes and it is FAR easier to do at construction, but after is OK - but you have a lot of dirt to dig.

Above grade, I used "trim coil" to protect the closed cell foam boards, but you could use one of the many concrete mastic products out there.

An excellent idea, but a LOT of work!

Steve

keachier · 05-28-13, 10:42 PM

Quote:

Originally Posted by stevehull

Bonjour Kiechier,

Tres bien and this is exactly what to do. I used rigid 4x8 foot closed 1 inch closed cell foam boards after spraying the walls with an elastomeric coating. Then I backfilled with sand.

A drain at the base will drain away any water.

Putting the insulation on the outside of the basement wall decreases condensation on the inside wall. In your area, the deep ground temp is about 44 F or so and with no insulation, the wall surface on the inside will be cold. Any air with a dew point above 44 will condense. The resulting environment is perfect for mold; damp, cool and dark.

The insulation on the outside concrete wall allows the inner concrete wall to stay warmer and condensation is minimized.

I have done this in several homes and it is FAR easier to do at construction, but after is OK - but you have a lot of dirt to dig.

Above grade, I used "trim coil" to protect the closed cell foam boards, but you could use one of the many concrete mastic products out there.

An excellent idea, but a LOT of work!

Steve

What is the elastomeric product you use prior to shoot urethane,Is this a membrane you heat that stick to concrete to seal from water...

stevehull · 05-29-13, 08:50 AM

There are a variety of rubberized elastomeric products for external poured concrete foundation walls.

The first were "roll on" out of a 5 gallon tub. Then a similar product came out that was sprayed on with a special gun that could shoot this very thick viscous liquid. Lately there are sheets that are "glued on". The sheets are wicked expensive.

I really like the spray on products. The trade names here in the States will be different from yours, but commercial contractors use this all the time. The gun is expensive, but you can spray quickly and get the job done fast.

For a single job, on your own home, the roll on product is probably the best. I will warn you that this is the messiest job I have seen yet and the nasty stuff sticks in your hair.

It is NOT a tar based product, but is a black elastomer that cures in about 12-24 hours. By vigorously applying it/working it into the concrete wall, with a heavy nap roller, the elastomer gets into cracks/crevices where a sheet would never completely seal.

I do recommend then using a closed cell foam ("pink board") to protect the elastomer and then to back fill with clean sand (no rocks). The sand allows frost to expand/contract far better than clay or other rough grade surface materials.

Let me look on line and find names of products. You do the same and let's compare notes.

Steve

Ryland · 05-29-13, 08:53 PM

Auto part stores sell head socks to cover your head and hair and they cost about a dollar, well worth it!

2" foam is twice as good as 1" and well worth it once you have the trench dug and if for some reason you can't dig all the way down, or even if you do dig all the way down adding a foam skirt to the house will help too, I tend to dig 2 to 4 feet down, depending on the foundation and soil type, run the foam that 2 to 4 feet down, then dig out 4 feet and sloping away from the house lay more 2" thick foam, cover with 6 mil plastic with drain tile at the outer edge and cover back over, this will take care of water in the basement from spring thaw as well.
with slabs on grade (no basement) we would dig down the foot of the foundation footer then out 4 feet to insulate the foundation.

keachier · 08-16-13, 07:32 AM

Tank's to all of you for good advice,I will not be able to do the work this year.Big mom had a long list of different job to be done this summer on the house,new shingles on all the roof, some alu siding around doors, windows etc.My last job will consist on installing a mini split,My choice go to senville aura 24000 btu that will be mod to be water sourced later.

05-27-13, 10:17 AM	#1
keachier Lurking Renovator Join Date: May 2013 Location: Mascouche Québec Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	outside basement insulation I plan excavating around the house to install drain and put urethane on outside concrete basement wall and cover it with mesh and concrete.Is thi a good idea.My thingking goes like this,if you can put insulation from exterior you cut cold between basement wall and floor and base of the exterior wall.

05-27-13, 12:19 PM	#2
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Bonjour Kiechier, Tres bien and this is exactly what to do. I used rigid 4x8 foot closed 1 inch closed cell foam boards after spraying the walls with an elastomeric coating. Then I backfilled with sand. A drain at the base will drain away any water. Putting the insulation on the outside of the basement wall decreases condensation on the inside wall. In your area, the deep ground temp is about 44 F or so and with no insulation, the wall surface on the inside will be cold. Any air with a dew point above 44 will condense. The resulting environment is perfect for mold; damp, cool and dark. The insulation on the outside concrete wall allows the inner concrete wall to stay warmer and condensation is minimized. I have done this in several homes and it is FAR easier to do at construction, but after is OK - but you have a lot of dirt to dig. Above grade, I used "trim coil" to protect the closed cell foam boards, but you could use one of the many concrete mastic products out there. An excellent idea, but a LOT of work! Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990

05-29-13, 08:50 AM	#4
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	There are a variety of rubberized elastomeric products for external poured concrete foundation walls. The first were "roll on" out of a 5 gallon tub. Then a similar product came out that was sprayed on with a special gun that could shoot this very thick viscous liquid. Lately there are sheets that are "glued on". The sheets are wicked expensive. I really like the spray on products. The trade names here in the States will be different from yours, but commercial contractors use this all the time. The gun is expensive, but you can spray quickly and get the job done fast. For a single job, on your own home, the roll on product is probably the best. I will warn you that this is the messiest job I have seen yet and the nasty stuff sticks in your hair. It is NOT a tar based product, but is a black elastomer that cures in about 12-24 hours. By vigorously applying it/working it into the concrete wall, with a heavy nap roller, the elastomer gets into cracks/crevices where a sheet would never completely seal. I do recommend then using a closed cell foam ("pink board") to protect the elastomer and then to back fill with clean sand (no rocks). The sand allows frost to expand/contract far better than clay or other rough grade surface materials. Let me look on line and find names of products. You do the same and let's compare notes. Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990

08-16-13, 07:32 AM	#6
keachier Lurking Renovator Join Date: May 2013 Location: Mascouche Québec Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	basement insulation Tank's to all of you for good advice,I will not be able to do the work this year.Big mom had a long list of different job to be done this summer on the house,new shingles on all the roof, some alu siding around doors, windows etc.My last job will consist on installing a mini split,My choice go to senville aura 24000 btu that will be mod to be water sourced later.

05-29-13, 08:53 PM	#5
Ryland Master EcoRenovator Join Date: Mar 2009 Location: Western Wisconsin. Posts: 913 Thanks: 127 Thanked 82 Times in 71 Posts	Auto part stores sell head socks to cover your head and hair and they cost about a dollar, well worth it! 2" foam is twice as good as 1" and well worth it once you have the trench dug and if for some reason you can't dig all the way down, or even if you do dig all the way down adding a foam skirt to the house will help too, I tend to dig 2 to 4 feet down, depending on the foundation and soil type, run the foam that 2 to 4 feet down, then dig out 4 feet and sloping away from the house lay more 2" thick foam, cover with 6 mil plastic with drain tile at the outer edge and cover back over, this will take care of water in the basement from spring thaw as well. with slabs on grade (no basement) we would dig down the foot of the foundation footer then out 4 feet to insulate the foundation.