Please, opinions about my new 2ch room

[Peter Breuninger]

OK, I am not a civil engineer so don't know what a screwpile is . I do know that having concrete walls is bad for bass response. So if that is what it means, you should build another room inside it with more flexible material. You will lose some space of course that you could put to decent use for insulation.

Very good advice. In fact, if I was to scratch build a room, it would have a concrete base floor, then three meters of soil, then four feet above that, a wood floor. Plaster walls a must. As an option... a large window looking out on Central Park or the Oregon coast. Keep drywall and concrete as far away from the room as possible. It needs to live and breathe like a fine concert hall. Forget after market fixes... band-aids in my opinion. It's all in the actual structure.

 

[joaovieira]

Zz, here are some coments about your post:

I am trying to get my head around the structural plan before making too many comments. I did get your Brazilian definition of condominium so far [very different from USA].

- You're right, the correct name is not Condominium, would it be allotment in English? I missed the word in english.

Please define a Brazilian screwpile [you did say concrete reinforced]. In USA it is a steel structural piece [piling] screwed in the earth for structural reasons, but maybe in Brazil it is the hole excavated by a screw & filled with a rebar cage and concrete.

The screwpile I mentioned is used to contain the soil and let the excavation of the new room be done. Most of the soil is made of sand or silt, no clay. We make the holes with a big screw, as deep as the double of the depth to be escavated.
Inside there is concrete and steel, like circular columns.
My intention is to use those screwpiles as outside walls for the room. The side that faces the room would be leveled to be a plane wall, and then make all the waterproof treatment on it. Over it I intend to use sheet rock or drywall, I dont know if just one sheet over the concrete or double with glass fiber inside.

Are these screwpiles going to be inside the perimeter of the structural walls of the house, or are they outside the perimeter? Are the screwpiles going to reinforce the existing structure of the house also? How deep will the screwpiles be below the finished audio room floor?

- The screwpiles are only for excavation issues. They are outside the perimeter of the house, in the garden, but two of the sides of my room touch two external walls, one that separate my property from one neighbor. Those walls have a foundation made of rock and concrete, and are about 60 cm deep.

Most important - were any studies done to determine whether there were any layers or other distribution of expansive clay in your soil?
How far down to bedrock?

- this I can answer tomorrow. I have the soil profile from surveys before construction. I have it in my office.

Is the existing area the crawl space under the main floor?

- it is a free area on the garden.

The foundation of the house itself is under each column, direct foundation on reinforced concrete.

Hope it helps.

Thank you again.

 

[microstrip]

Very good advice. In fact, if I was to scratch build a room, it would have a concrete base floor, then three meters of soil, then four feet above that, a wood floor. Plaster walls a must. As an option... a large window looking out on Central Park or the Oregon coast. Keep drywall and concrete as far away from the room as possible. It needs to live and breathe like a fine concert hall. Forget after market fixes... band-aids in my opinion. It's all in the actual structure.

Peter,

Why do you think that plaster walls are a must and better than drywall or wood panel walls?

 

[joaovieira]

Very good advice. In fact, if I was to scratch build a room, it would have a concrete base floor, then three meters of soil, then four feet above that, a wood floor. Plaster walls a must. As an option... a large window looking out on Central Park or the Oregon coast. Keep drywall and concrete as far away from the room as possible. It needs to live and breathe like a fine concert hall. Forget after market fixes... band-aids in my opinion. It's all in the actual structure.

Peter,

Thank you so much for your comments. That what I am looking for, a material to put inside the concrete walls that would be good for acoustics. Would drywall be bad? Please let me know what type of materials would be good to the inside walls.

 

[joaovieira]

Peter,

Why do you think that plaster walls are a must and better than drywall or wood panel walls?

Microstrip, I have the same question. And please, I am looking forward to your coments about ps audio 10.

 

[zztop7]

Precast Concrete Monolithic Vault

Hi Joaovieira,
Thank you for the rely. The "allotment" sounds like a planned community of single family residences [close to zero lot line].

You wrote: "- it is a free area on the garden."

If this is the situation I would excavate, prepare the area [compacting, then geotextile & gravel], and then bring in by crane a precast concrete monolithic vault. This would be simpler and you could waterproof the exterior of the vault ahead of delivery. With certain products you could also eliminate most vapor intrusion. You should be able to have the concrete-vault company do a proper waterproof concrete mix. Probably save you time & money.

I will go into the waterproofing products after you research vaults in your area.

Best to you,
zz

 

[microstrip]

Microstrip, I have the same question. And please, I am looking forward to your comments about ps audio 10.

The PSAudio 10 is stored under some old drapes and protector dust sheets - I am making some changes to my listening room to enlarge it a bit and this week the workers have been building a new wall using drywall and QuietGluePro http://quietrock.com/adhesives/quietglue, that I expect will operate as a bass trap. As soon as it dries completely (about two weeks) I will remeasure my room.

 

[joaovieira]

Concrete vault would be much more expensive here. For the size of the room and not much repeated pieces. And hand labor here is still not much expensive as in the US.

I will probably work on the screwpiles to make them the main wall, using waterproofing products in and on a grout used to leveling the wall. And then applying a second wall due to acoustic issues.
I will still think on making a gravel wall between the soil and the screwpiles, so I can create a preferencial way to the rainning water. What do you think?

 

[joaovieira]

The PSAudio 10 is stored under some old drapes and protector dust sheets - I am making some changes to my listening room to enlarge it a bit and this week the workers have been building a new wall using drywall and QuietGluePro http://quietrock.com/adhesives/quietglue, that I expect will operate as a bass trap. As soon as it dries completely (about two weeks) I will remeasure my room.

Thanks.

 

[zztop7]

Football field

FOOTBALL FIELD

Analogy: If you could lay out all the surface area of the internal pores of one gram of activated filter charcoal [air or water], the area would equal a football field. The pores of concrete are similar in that the pores create a galaxy for moisture intrusion.

I will reply tomorrow when I have more time for product discussion, structural considerations, and drainage.

Best to you,
zz.

 

[zztop7]

What I would do

Fictional Story – Instead of advising you, I am going to tell you what I would do if I found an area sunken in the ground on my property with your parameters of perimeter concrete reinforced screwpiles. This is for a structural room for many uses [acoustic improvements would be added if that was the final direction].

zz finds a very large cover that is keeping a sunken area from filling with rainwater.

zz investigates and finds that the sunken concrete walls are scalloped on the vertical surfaces, and they have proper rebar [in fact epoxy rebar- ? is the ground corrosive?]. The concrete had been placed ~25 feet deep.

zz excavates further down to ~14 feet / compacts the soil / places geotextile fabric / lays in a bed of drain gravel approximately 2 feet deep / places in at least 3 layers of very thick plastic fabric – crisscrossed & taped if necessary. There is debate: plastic vs. NO plastic. I am on the plastic side.

zz starts the floor & monolithic connection rebar / #4 rebar [1/2 inch] – this size due to critical spacing & bends / rebar 6” OC [on center] / at the walls the rebar is bent upward at least 18 inches – preferably going into the deeper spaces created by the scalloped wall [the result of the circular concrete screwpiles touching & bonding / the rebar is elevated with plastic stands so that it sits 3 inches above the thick plastic.

zz orders the high strength concrete with ¼” & smaller aggregate / high sand mix / the additive Xypex [water & some vapor control] http://www.xypex.com/ will be in the mix & synthetic fibers for initial crack control & stainless steel fibers - http://www.nycon.com/ncwp/
The concrete will be poured and vibrated to a depth of 6 inches [not a wet batch – it is weaker] & several samples will be poured in tubes on the side. Make sure the concrete supplier knows that you will be taking these samples and having them sliced & tested to confirm the ingredients and strength.

XYPEX is used worldwide in Billion $ dam & waterfront projects. It is also used in backyard projects.

zz realizes that the strength of the walls is in place [not water & moisture control]; therefore the forms for the flat walls can be built 2 inches from the thickest cross section of the concrete screwpiles.
http://www.ductal-lafarge.com/ to learn about concrete with no rebar used for major bridges.
You could probably go down to 1 inch, but harder to vibrate in the mix.
The scalloped walls are extensively cleaned & treated so the new concrete will bond.
Remember that rebar zz bent upward into the scalloped wall area; this wall will connect here and if the first pour is treated properly you will not have a cold joint. You will have a monolithic structure.
No additional rebar is needed due to the existing concrete screwpile wall. zz orders the high strength concrete with ¼” & smaller aggregate / high sand mix /the additive Xypex [water & some vapor control] http://www.xypex.com/ will be in the mix & synthetic fibers for initial crack control & stainless steel fibers - http://www.nycon.com/ncwp/ . NOT A WET MIX. Vibrate in the mix.

Best to you,
zz.

 

[joaovieira]

Zz, I liked very much. Thank you, I will study your suggestions with care. Any doubt I will get back to you.

Cheers,

João

 

[zztop7]

Water does go up

Water does go up / Drainage Issues - Now that I have gone over some structural ideas, drainage must be addressed.
Water travels through the earth by pressure - gravity pressure or water pressure or vapor pressure, etc. The moisture in the earth is going to take the easiest route, and when anyone digs into the Earth, they disturb established routes. For example: very old house [almost 100 years old] with a year round very dry basement on top of a very tall steep hill / excavation of the side of the hill / tall concrete wall placed into the hill for a modern parking garage / now the basement of the very old house above the parking garage is flooded everyday / concrete wall has produced a dam blocking the previous easiest water routes, and now the easiest route for the water is up and into the house [try proving this in court for damages - near impossible].
Therefore, before the concrete floor pour, zz would place 2 vertical drainage pipes near each future wall extending deep into the drain gravel during the floor pour . The drainage pipes would be capped. They would be for future use [sump pump, etc] if there is a moisture problem.
Best to you,
zz

 

[joaovieira]

Zz, thank you so much, great suggestion that one of the drainage pipes. I will certainly consider it.