FB Board and moisture

[hodgey1]

Where I live it hasn't stopped raining for weeks, 18.75" have fallen since May 1 .

I was warned by a builder/forum member not to use FB board due to his constant worries of getting it wet during his build. I can not stress enough what a bad decision it was for me to use FB board. It has taken what was supposed to be a fun project and made it extremely stressful.

Am I worrying to much? I need someone to weigh in how concerned I need to be about it getting damp/wet. Am I going to have structural problems? I keep it tarped when I'm not working on it, but even so it seems to be very moist when I uncover due to curing concrete/small leaks of rain.

Help

[deejayoh]

Re: FB Board and moisture

I responded on your other thread about this. The FB board shouldn't break down with moisture. It will absorb it but should be structurally sound so you don't need to worry about that. What you do need to do is figure out how it is getting wet even though it is under cover. If it's coming through your slab you have a bigger issue as you'll never be able to keep the oven dry.

[hodgey1]

Re: FB Board and moisture

Hi DJ, if you look at the drawing I just posted you will see that under drain should not be an issue. The problem I'm having is from the never ending rain and moisture build up under tarp after prolonged periods being covered. Your comment on the FB board staying structurally sound makes me feel a bit better, so it will stay strong even if exposed to moisture?

[deejayoh]

Re: FB Board and moisture

ah - good deal. Looks like plenty of drainage.

Yes, it should be structurally sound. The spec sheet says so , and more significantly other builders have had it get wet and not had it problem with it breaking down. You'll just need to get it dried out at some point with a stretch of hot weather and then get your housing on!

[hodgey1]

Re: FB Board and moisture

Thanks for the encouraging words. I'm not sure we are ever going to have dry weather here. I have a lot of time invested on my build and would cry if the insulation collapsed.

[deejayoh]

Re: FB Board and moisture

Well, I made it through in Seattle - seems like PA would be easier!

[Les]

Re: FB Board and moisture

Thanks for the encouraging words. I'm not sure we are ever going to have dry weather here. I have a lot of time invested on my build and would cry if the insulation collapsed.

Deejay is spot on. As a test, I loaded a piece of board with weight and left it out side in rain and snow for the winter. Pretty extreme compared to what the product will normally see. It was in great shape after it dried.

[Bec1208]

Re: FB Board and moisture

Deejay is spot on. As a test, I loaded a piece of board with weight and left it out side in rain and snow for the winter. Pretty extreme compared to what the product will normally see. It was in great shape after it dried.

Nice empirical approach. I received the suggestion below to coat the outside edge with a thin coat of mortar . I thinned left over mortar to the point it could essentially be spread over the cf board's edges with a brush. It made the board easier to work around and gives it some protection from dampness. Good luck with your build.

Bruce,

When you get done trimming the Ca Sil to where you want, take your leftover mortar as you lay your bricks and render the sides of the Ca Sil board. The mortar will keep the Ca Sil from getting damaged, broken, dented while you do your dome.

[hodgey1]

Re: FB Board and moisture

Thanks for the information all. It's making me feel a bit less worried.

[Les]

Re: FB Board and moisture

Deejay is spot on. As a test, I loaded a piece of board with weight and left it out side in rain and snow for the winter. Pretty extreme compared to what the product will normally see. It was in great shape after it dried.

Here is another test I did (board was dry though). 3/4 ton truck, just the leading edge got a little stressed. The board is a great product...