New Home Studio build in Japan

#61

given you should have some flashing installed to ensure water rolling down the sides is expelled outside rather than in, you could probably have them add a dense concrete (perhaps mixed with some elastic compounds to ensure it doesn't crack) layer on the face of foundation and have the flashing overlap that which will prevent water from getting in and causing a potential for separation. its also not the structural support for the walls so it should be ok.

#62

Hi Glenn

Thank you so much for your input!

On top of the exterior sheathing, there will be a waterproof sheet, furring strips to mount the siding (also used to create space under the siding to let air through), and finally the siding. There also will be flashing between the siding and the foundation.

Do you by chance have an example of the elastic compound? (like a product name?)
I may not be able to get the same thing, but I could use that as a reference.

Also when you say "and have the flashing overlap that" you do mean just the top corner part of the concrete, correct?

Thanks again!
Keith

#63

there are a number of additives - elastic powders, fibers, even steel fibers etc. which when added to the high strength concrete can prevent cracking. now 20mm will be tricky since its almost a skim coat... i would secure a 10mmx10mm mesh to the existing concrete using concrete screw - some that sets off about 8-10.. then have then use some forms to pour into unless then feel confident they can apply by hand or spraying.

Zypex, Nomex are water proofing agents which fit this type of crack prevention. Sikacem and Sikament are products with fibers and/or plasticizers which may also fill the role.

yes, flashing sits on top corner to prevent water getting in under the sill plate.

#64

Hi Glenn

Thank you so much for the information and your thoughts!

I'll have to look into and see what the material you mentioned are called here in Japan.

Mesh with high strength concrete (+ other stuff) makes sense. But the company is probably going to try to find a cheaper/quicker fix. They said "We were thinking possible using tile ..." and I said "I don't think so!". I mean, that doesn't sound right to me at all since I had so many pieces of tile come off the bathroom, swimming pool, etc. when I lived in the States.

A post I made on another forum (which you may have seen), people have suggested possibly using cement board, or ledger board. When I looked into different material available for ledger boards other than wood, one material that came up was PVC. I guess, PVC boards that they make for use around window and/or door framing outside. They're also available as large sheets but they're expensive.

Do you have any thoughts on using cement board or PVC?

I really appreciate your help

Keith

#65

cement board could be an option esp with some thin set to bind to the existing cement. the PVC panels sound costly and might leave a space for moisture to get into.

#66

Hi Glenn

Thanks again for your reply.

So I guess it'll be a toss up between mesh + concrete with additives, or cement board with thin set.

Today, the builders were again talking about tiles (10mm thick) + thin set (10+mm). Probably to save money and/or because they don't trust to use the concrete people that screwed this up to begin with. I would think that tiles will have a high chance of falling/coming off eventually with its own weight or thin set cracking. So I'm thinking no, but any thoughts on this?

Thank you!
Keith

#67

if they have a warranty on the installation, and the tiles are cost effective, it could work.

#68

Hi Glenn

Thank you for your response

I spoke to the guy from the company today. He went and measured the space between the plywood and the ledge of the concrete footer which is supposed to be 33.5mm, or at least 30mm. Well, not surprisingly they were all different depending on where he measured but they were over all short of what it was supposed to be.

Anyway, they will fix it but when he called and asked the guy from a person from the company that makes cement board, he was told that use of cement board underground was not recommended for the reason that the ground could contain much higher level of water/moisture which could effect the chemical compound (of the cement board in a negative way.

And I decided against using tiles because they won't match with the rest of the house (which will be concrete at the bottom).

So I guess, it will be mesh + concrete with additives after all. When it's actually done, I will let you and others know what happened.

Thanks again!
Keith

#69

Hi Glenn (and everyone)

I hope you’re around to see this post. So it’s taking forever for them to fix the concrete. They say that it’s difficult for them to just add (pour) 1-2cm so they want to add about 4-5cm and use something bigger/thicker than 10mmx10mm which is fine by me. Of course I’ll have the mesh or rebar or whatever screwed on to the existing concrete.

Right now there’s a layer of structural plywood install right above the concrete footing as you can see in the picture on post #60 of this thread. They say that they’ll cover up the plywood so that the new concrete won’t get on the plywood surface. My concern is: Wouldn’t the moisture from the new concrete seep through the existing concrete into the plywood and damage them? Or should I be ok?

Obviously, they don’t want to take off all the plywood, but then again, if the plywood end up damaged, they’ll have to replace them which would be a pain, a waste of time/material.

Any thoughts?

Thanks
Keith

#70

Hello Keith, I am not Glenn nor another professional but I would paint the areas of plywood that will be in contact with the new, wet concrete with a couple of coats of exterior paint as it protects exterior walls from rain and in your case it only needs to protect the wood until the concrete has dried, so should be sufficient.

#71

although it probably needed to be exterior grade plywood... but if not, then a wood sealant or paint should help protect it.

#72

Thank you Starlight and Glenn

I've been told that the type of plywood is "structural" and strong against moisture, etc. but I don't know if its "exterior grade" (I'll check with them).

Perhaps I didn't explain myself clearly enough. The outer part/the sides of the plywood will be covered so there's no concern with moisture there. I drew a quick picture. I hope this kind of explains the situation.

So the concrete will be added from the sides, and will go up to the same height as the existing concrete. The plywood is sitting on top, but a little bit tucked in from the edge of the existing concrete. My concern/question is will the moisture from the new concrete "seep through" from the "sides of existing concrete" into the plywood through the "bottom side/underside of the plywood" (the part of the plywood that's sitting/touching directly on the existing concrete)? The part of the plywood that can't be painted unless I removed the plywood once.

I don't know if that makes any sense.

Thank you
Keith

#73

The edges of plywood will be more susceptible to soaking up water so make sure you protect the wood from the wet cement.

#74

Thank you, Starlight

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