Hi. I'm building a floor in an attefallshus and today I started with the subfloor. I have screwed boards flat onto the floor joists underneath and placed fiber cement boards in all the sections resting on the boards. But the question is whether the seams between the boards can just be sealed with tape, or with an extra piece of board over the seam, or if I need to place joists under all the seams where the board ends rest? Has anyone else here installed a subfloor with fiber cement boards, and if so, how did you do it?
I'm doing the same thing and applied a bead of sealant before joining the boards. But I'm considering adding something else over the joints. Tape or pieces of the roofing felt I have lying around.
On Byggmax, it says the following about their fiber cement board: The board’s horizontal joints should be covered with a joint strip to protect edges/construction from moisture penetration. Alternatively, the board joint can be sealed with sealant.
Sorry if I'm hijacking the thread now! Are you going to install any form of wind protection in the cavities before the insulation to prevent potential drafts in the construction?
If anyone reads this and can advise (us), would it work with Bison wind protection in the framework on top of the fiber cement subfloor, with the smooth side down, and then after laying the insulation, lay Bison again with the smooth side up? Then it should protect the insulation from moisture from above at least before the floor is laid, as well as moisture/draft from below. Is there any risk in doing so?
On Byggmax, it says the following about their fiber cement board: The board’s horizontal joints should be covered with a joint strip to protect edges/construction from moisture penetration. Alternatively, the board joint can be sealed with sealant.
Sorry if I'm hijacking the thread now! Are you going to install any form of wind protection in the cavities before the insulation to prevent potential drafts in the construction?
If anyone reads this and can advise (us), would it work with Bison wind protection in the framework on top of the fiber cement subfloor, with the smooth side down, and then after laying the insulation, lay Bison again with the smooth side up? Then it should protect the insulation from moisture from above at least before the floor is laid, as well as moisture/draft from below. Is there any risk in doing so?
Works perfectly fine to borrow the thread, just nice.
I wasn't planning on adding any extra wind protection, the fiberboards should be dense enough as it is. However, I do plan to seal all the corners carefully after screwing in all the boards. I might also run a bead of sealant along all the longitudinal edges, or alternatively, some foam sealant.
I wasn't planning on adding any extra wind protection, the fiberboards should be dense enough as it is. However, I do plan to seal all the corners carefully after screwing in all the boards. I might also run a bead of sealant along all the longitudinal edges, or alternatively, some foam sealant.
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· Västra Götaland
· 3 534 posts
The secondary purpose of the board is to keep rodents away from the insulation, so if you have larger gaps, patch them with either the same board or a strip. I don't think sealant will stop a mouse looking for a home 
Member
· Västra Götaland
· 3 534 posts
If your records are dense then I don't think the windbreak has any function at all.
In our house built in 1960, the fibercement boards (Eternit) overlap by 10cm at each joint, and no mice have entered there.
Extra wind protection should be unnecessary, possibly if the house is located on an exposed cliff by the sea, otherwise, I don't see much meaning in it.
I had a gap between a house and an extension, the gap was about 30 mm wide and 220 mm deep. I placed a bead of sealing foam at the bottom and let it cure. Then I added crushed stone 4-6 on top of that, and then sealing foam all the way up. The mice don't stand a chance to get in there!
I had a gap between a house and an extension, the gap was about 30 mm wide and 220 mm deep. I placed a bead of sealing foam at the bottom and let it cure. Then I added crushed stone 4-6 on top of that, and then sealing foam all the way up. The mice don't stand a chance to get in there!