Browse Forums Owner Builder Forum Re: Pre-cast Concrete House Build Perth 34Nov 27, 2020 8:08 am dachopper I am very close to the saltwater spray - so trying to pick the best building materials that are going to last the longest. Check out the various codes for marine environmental and maintenance requirements Designer,Engineer (Civil,Const & Envir),Builder,Concrete & Masonry Contract.Struct Repairs Re: Pre-cast Concrete House Build Perth 35Nov 27, 2020 12:14 pm dachopper alexp79 Nope, I am talking about water vapours generated inside the house, e.g. bathroom, laundry, kitchen/cooking, breathing, etc. Even when the temperature gradient is not there, vapours will still be eventually turning into the moisture on the backside of your concrete as well as inside internal leaf and eventually corroding reinforcement and damaging the structure. If you will be putting in gyprock on top of your concrete, then a lot of moisture will be accumulating between your concrete and gyprock and gyprock will be eventually rotting. If you are planning to render out, then the render will be falling off. Gyprock + mineral insulation wall, on the other side, is vapour permeable, so the water vapours find they way out as they are easily travelling through the gyprock and mineral insulation and then evaporate through the cavity. Even if they condensate somewhere in the middle, they will easily dry out later. Concrete itself is not very vapour permeable structure (depending on the density, it can be either semi-permeable or not permeable), but XPS has almost zero permeability. You will be completely locking in all the water vapours/moisture inside the structure. Standard ventilation won't be enough, you would need to either go with full blown ERV system which handles ventilation as well as regulates moisture levels or just try living with the windows always open in pretty much all the rooms and esp. south facing ones. "Even when the temperature gradient is not there, vapours will still be eventually turning into the moisture on the backside of your concrete as well as inside internal leaf and eventually corroding reinforcement and damaging the structure." Please correct me if I'm wrong, but. My understanding is The benefit of the concrete wall is precisely that the reinforcement is protected from moisture because it is within the concrete. Without the concrete wall it would be exposed ( as cold steel ) directly to the moisture and corrode. The concrete as you say is almost inpermeable and I am very close to the saltwater spray - so trying to pick the best building materials that are going to last the longest. Having said that - we do have a huge amount of windows/ openings / sunlight / skylights in our design, and our Southern wall abuts directly to the neighbours for at least 50%, meaning most of the wall will be protected from the elements. We don't have almost any southern facing windows. Concrete is generally waterproofed or protected with render or cladding (when outside) if the want is to protect it from water. It becomes impermeable only at very high densities (e.g. used for massive structures), but I really doubt it is applicable to residential buildings, so in your case it will still likely to be semi-permeable. As I said, I am not worried about elements, I am worried about water vapour from inside the house as it will be creating the main damage. You do not constantly keep all your windows open. Re: Pre-cast Concrete House Build Perth 36Nov 27, 2020 2:55 pm alexp79 dachopper alexp79 Nope, I am talking about water vapours generated inside the house, e.g. bathroom, laundry, kitchen/cooking, breathing, etc. Even when the temperature gradient is not there, vapours will still be eventually turning into the moisture on the backside of your concrete as well as inside internal leaf and eventually corroding reinforcement and damaging the structure. If you will be putting in gyprock on top of your concrete, then a lot of moisture will be accumulating between your concrete and gyprock and gyprock will be eventually rotting. If you are planning to render out, then the render will be falling off. Gyprock + mineral insulation wall, on the other side, is vapour permeable, so the water vapours find they way out as they are easily travelling through the gyprock and mineral insulation and then evaporate through the cavity. Even if they condensate somewhere in the middle, they will easily dry out later. Concrete itself is not very vapour permeable structure (depending on the density, it can be either semi-permeable or not permeable), but XPS has almost zero permeability. You will be completely locking in all the water vapours/moisture inside the structure. Standard ventilation won't be enough, you would need to either go with full blown ERV system which handles ventilation as well as regulates moisture levels or just try living with the windows always open in pretty much all the rooms and esp. south facing ones. "Even when the temperature gradient is not there, vapours will still be eventually turning into the moisture on the backside of your concrete as well as inside internal leaf and eventually corroding reinforcement and damaging the structure." Please correct me if I'm wrong, but. My understanding is The benefit of the concrete wall is precisely that the reinforcement is protected from moisture because it is within the concrete. Without the concrete wall it would be exposed ( as cold steel ) directly to the moisture and corrode. The concrete as you say is almost inpermeable and I am very close to the saltwater spray - so trying to pick the best building materials that are going to last the longest. Having said that - we do have a huge amount of windows/ openings / sunlight / skylights in our design, and our Southern wall abuts directly to the neighbours for at least 50%, meaning most of the wall will be protected from the elements. We don't have almost any southern facing windows. Concrete is generally waterproofed or protected with render or cladding (when outside) if the want is to protect it from water. It becomes impermeable only at very high densities (e.g. used for massive structures), but I really doubt it is applicable to residential buildings, so in your case it will still likely to be semi-permeable. As I said, I am not worried about elements, I am worried about water vapour from inside the house as it will be creating the main damage. You do not constantly keep all your windows open. So, a good recirculating system, or having some external walls that are not concrete would remove the problem you think? Re: Pre-cast Concrete House Build Perth 37Nov 27, 2020 8:09 pm dachopper alexp79 Concrete is generally waterproofed or protected with render or cladding (when outside) if the want is to protect it from water. It becomes impermeable only at very high densities (e.g. used for massive structures), but I really doubt it is applicable to residential buildings, so in your case it will still likely to be semi-permeable. As I said, I am not worried about elements, I am worried about water vapour from inside the house as it will be creating the main damage. You do not constantly keep all your windows open. So, a good recirculating system, or having some external walls that are not concrete would remove the problem you think? Partially the issue can be addressed if you replace XPS with EPS (which is semi-permeable) or mineral insulation (better). But I would still be thinking about installing ERV for the solid walls made of concrete. Re: Pre-cast Concrete House Build Perth 38Nov 28, 2020 11:12 pm alexp79 dachopper alexp79 Concrete is generally waterproofed or protected with render or cladding (when outside) if the want is to protect it from water. It becomes impermeable only at very high densities (e.g. used for massive structures), but I really doubt it is applicable to residential buildings, so in your case it will still likely to be semi-permeable. As I said, I am not worried about elements, I am worried about water vapour from inside the house as it will be creating the main damage. You do not constantly keep all your windows open. So, a good recirculating system, or having some external walls that are not concrete would remove the problem you think? Partially the issue can be addressed if you replace XPS with EPS (which is semi-permeable) or mineral insulation (better). But I would still be thinking about installing ERV for the solid walls made of concrete. That is good to know, from memory, I think EPS foam is an easy option I could change to, because the build is in the spray zone, I had a look an the building codes say we have to use a higher grade concrete, which I am guessing means it is more waterproof. Re: Pre-cast Concrete House Build Perth 39Nov 29, 2020 9:03 am Hey Dachopper Yep without data and proofs you are only guessing BTW, There are a few EPS & Esky Homes built in perth. May I suggest you look to more traditional building materials and get it properly engineered and certified hth Designer,Engineer (Civil,Const & Envir),Builder,Concrete & Masonry Contract.Struct Repairs Ideally you would engage a landscaper to give you some insight what they may need in the space to make your vision come to life… 1 13623 We've had the offer of a short term tenant whilst waiting for CDC/DA home approval and demolition for our knock down rebuild. It would achieve a pretty low rent as it's… 0 13744 |