How to handle post on the slab

[pgillner]

I am in the process of converting an existing carport into a garage. I have cast a slab level with the pillars on which the posts stand. The slab is almost level with the ground level, so I am building a row of leca blocks on the slab which I will then place the wall on. See the images below.
Now to the problem; how should I protect the lower part of the post from moisture and rain? The siding will end about 1 dm above the slab. Furthermore, the garage will be insulated and I want to maintain 15 degrees inside. In the gap between the post and the leca blocks, a lot of cold air comes in; how should I seal this?

Please help me with ideas for this somewhat unique project.

IMAGE INSIDE IMAGE OUTSIDE

 

[saturnus]

You probably should have thought about this before you built the lecan. It would have been easiest to dig out and raise the plinth or make a new one. But you don't show how it looks at the top, maybe you don't need the post anymore, and the wall takes up the load from the roof. If that's the case, you can just cut off the post at the top of the lecan, insert a piece of leca into the compartment and finish it off.

 

[pgillner]

You should have thought about this before you built the leca. The easiest would have been to dig out and raise the plinth or make a new one. But you don't show what it looks like at the top, maybe you don't need the post anymore, and the wall takes up the load from the roof. If that's the case, you can simply cut off the post at the top of the leca, insert a piece of leca in the gap, and smooth it out.

As I wrote, it's an existing carport with a proper roof that the posts hold. The walls I'm putting up between the posts (on the leca blocks) are not load-bearing in any way. The situation is now as it is. What should I do?

More pictures:

 

[saturnus]

Okay, lift the roof a bit (10-20mm) to free the post. Cut it at the height of the lecan. Get a new anchor iron (byggmax) and bolt it to the existing post iron so that they go up high enough for you to bolt them to the post (a bit later). Place board=form on each side of the lecan, and pour concrete again in the opening at the same height as the lecan. Once that's set=dried for 2-3 days, lower the post between the two irons and bolt it down. Also, don't forget a bit of foundation paper between the wooden post and the cement.
I hope I've explained it properly, otherwise someone else will do it... If you lift the roof 20mm, you'll have to cut the post according to this measurement so that it ends up correct when you lower the roof.
It would have been easier to make the wall load-bearing along its entire length and skip the posts.

 

[pgillner]

Okay, lift the roof up a bit (10-20mm) so that you free the post. Cut it at the height of the leca. Get new anchor iron (byggmax) and bolt it to the existing post iron, so that it goes high enough so you can bolt it to the post (a little later). Place board=form, on each side of the leca, and pour concrete to fill the opening to the height of the leca. When this has set=dried for 2-3 days, lower the post between the two irons and bolt it. Also, don't forget a piece of foundation paper between the wooden post and the cement. I hope I've explained it well, otherwise someone else will come along to do this... When you lift the roof 20mm, you need to cut the post according to this measurement so that it fits right when you lower the roof. It would have been easier to make the wall load-bearing along its entire length and skipped the posts

Thanks for the answer. Yes, I guess it will have to be like that. Otherwise, I wanted to keep it simple by keeping the posts and "just enclosing" the carport to make it a garage. But, well, if there is no other good solution, it will probably have to be as you described. There are no doubts, I understand what you mean.

 

[pgillner]

Okay, lift the roof up a bit (10-20mm) so that you release the post. Cut it at the level of the Lecas. Obtain new anchor iron (byggmax) bolt it to the existing post iron, so that they go high enough, so you can bolt them to the post (a little later). Place boards=form, on each side of the Lecas, and cast the opening in level with the Lecas. Once this has cured=dried 2-3 days, lower the post between the two irons and bolt it in place. Also, don't forget a piece of foundation paper between the wooden post and the cement. I hope I have explained, otherwise someone else will do this....if you lift the roof 20mm, you need to cut the post according to this measure, so that it lands correctly when you lower the roof. It would have been easier to make the wall load-bearing along its entire length and skip the posts

How does it work if you let the post remain, bolt new irons, and cast around the post?

 

[pgillner]

No more suggestions for a SIMPLE solution to this?

 

[jakim]

Of course, you can cast the post as it is. The only thing that happens is that you get a "köld brygga" where the post stands. If you then plaster the leka blocks and the casting, you get an invisible solution.

 

[pgillner]

Of course, you can cast the post as it stands and goes. The only thing that happens is that you get a "cold bridge" where the post stands. If you then plaster the leka blocks and the casting, you get an invisible solution.

How is it in the long run? No risk of the post rotting from the inside if it's cast in place?

 

[Mikael_L]

How does it last in the long run? Is there no risk that the post rots from the inside if it is embedded?

There should absolutely be a risk that the post rots/molds.

If you don't want to follow, for example, saturnus's suggestion, then the measure you take must meet the following "requirements."

The wood material (post) must be protected as well as possible from moisture intrusion, i.e., all moisture that can attack from the outside but also the moisture that concrete, mortar, and Leca can provide to the post. You can consider the concrete to have 100% rH, but the diffusion rate is not that high. So compared to, for example, rainwater splashing from the outside, the post does not become quickly damp. The unfortunate part about the moisture from the concrete (etc.) is that it moistens your wooden structure 24/7 all year round.

The second requirement is that, apart from this, you must allow drying in some (optional) direction.

Finally, the drying rate must always be greater than the moistening rate.

So if you manage to wrap the post with diffusion-tight plastic against all concrete/Leca sides, weather protect it from the outside, and finally keep an option for upward/inward drying, it can probably work well. But it could probably still be classified as a somewhat risky construction.

 

[saturnus]

Exactly, listen to mikael_L now, and don't encase the post, everyone on this Forum should know that. Sure, it will probably last for 10 years, but then someone else will have to break it all up to restore something that went wrong unnecessarily due to ignorance.

 

[Mikael_L]

I have a question.

How well does expanding foam stop moisture?

If pgillner were to apply expanding foam in the space between LECA and the post. Will the expanding foam become saturated with moisture and eventually damage the post?
Does anyone know about the properties of expanding foam?

Because if this works, then it might be enough to have something tight and weatherproof on the outside, expanding foam between the post and LECA, and finally avoiding splashing water inside the "garage," so that side can be free and breathe.

OK, an unconventional solution, hardly "by the book" I think.

edit:
I looked a bit more at the picture from the inside. There is a fairly decent distance between the inside of the LECA and the inside of the post. It might be possible to saw out a fairly small piece of LECA that can be fitted into the hole and mortared in place there. But make sure the piece has at least 1-2 cm free from the post. Then any moisture from the post can ventilate upwards. And then the inside of the LECA can be plastered to reduce the risk of water getting in from inside the garage.

 

[pgillner]

... it will probably be that I cut the posts (3 on each side) and pour concrete in the space between the lecka blocks. A bit more work, but it will provide good protection against moisture/rain/water that may come from outside. Since the walls are basically already in place and can take the load from the roof, I will probably not prop up the roof or lift it 10-20 mm as suggested, but just cut off and pour up to then bolt the post to new iron that has been cast in.

... or is there another way?

 

[Herman hedning]

cast with expansion mortar all the way up to the bottom edge of the post, but don't forget the syllpapp