Workshop Extension and Updates (2 Viewers)

[PAToyota]

Well, for me, it was enough work to mix the concrete for the foundation! Aside from that, cost. Doing it yourself, the materials for block are going to be less than a similar amount of concrete and forms for it. The guys that do poured foundation walls typically have standard forms for a full basement. I'd have to call around to see if they'd have forms for a lower wall like this.

I did consider ICFs - the insulated concrete forms. They'd have allowed me to form things up however I wanted without the cost of plywood and bracing or renting forms. But then I'd be back to the issue of mixing up the concrete.

 

[alia176]

Ok, thanks for that info. I see ICF's being sold on local CL but wasn't sure if I wanted to purchase them for my garage project.

I can definitely lay down blocks so I think I'll head that direction in order to save money. Additionally, my stem wall will come out of the ground a fair amount since I need the walls to be higher 10' and for that, blocks sounds like an easy way for a DIY to build up.

I noticed that the blocks for our home foundation were filled with concrete. Will be doing this on your project?

 

[Delancy]

I noticed that the blocks for our home foundation were filled with concrete.

And rebar.

@ PA,

Is there some code requirement that prohibits filling a ditched trench there?

Even on the deepest of foundations I've seen, locally, we tie steel in cages, lower into a ditched trench, and pour to grade.

Curious why it was necessary to expose both sides of the stem wall, necessitating block or forms, considering it's not a full basement.

 

[PAToyota]

Additionally, my stem wall will come out of the ground a fair amount since I need the walls to be higher 10' and for that, blocks sounds like an easy way for a DIY to build up.

I noticed that the blocks for our home foundation were filled with concrete. Will be doing this on your project?

Check on reinforcing for a wall of that height. As for grouting the cells solid, you'll want to check on local codes about that. Around here they are very rarely all grouted solid - only the ones with reinforcing are grouted solid. The project I showed the foundations for earlier has 22' tall walls and has #4 bars at 4' o.c. So only that one cell in 4' is grouted solid. I've heard that in other areas it is typical to have all the cells grouted solid.

 

[PAToyota]

Is there some code requirement that prohibits filling a ditched trench there?

Even on the deepest of foundations I've seen, locally, we tie steel in cages, lower into a ditched trench, and pour to grade.

Curious why it was necessary to expose both sides of the stem wall, necessitating block or forms, considering it's not a full basement.

I'm not quite sure that I understand. But I think that you mean you'd have a foundation several feet thick - up to grade - and then build on that. I guess that would depend on how deep your frost depth is. Again, it is cheaper to have a thinner foundation (here it is 8") by the required width (16" was required here) and then build from that up to grade (36" frost depth) with block rather than have a 16" x 36" deep foundation. For every 10' of foundation wall, I only have about 9 c.f. of concrete instead of nearly 40 c.f. if I just poured the whole trench full.

[edit] And even if I formed the foundation wall and continued to use concrete, I'd only need an 8" wall so for that 10' of wall I'd only have an additional 15.5 c.f. of concrete and still come in about 15.5 c.f. less than pouring the whole trench.

 

[PAToyota]

And I do appreciate the questions. Although I have over twenty years of experience, it has all been in the general northeast area. Even around here you see different ways of doing things. But what is perfectly common here is apparently unseen on the West Coast or other areas.

 

[alia176]

Thanks for humoring us! This is a fascinating process, to me at least. More questions coming your way!

- is your footer 16" wide? It seems wider from the pic hence the question. Our code requires twice the wall thickness, so 16" wide for a 8" wall.

- what is the depth of the footer that you poured? It appears to be 6" but not sure.

 

[PAToyota]

I only needed an 8" thick by 16" wide footer. With learning to use the mini-ex, it is closer to 10" thick by 24" wide. The bottom of the footer is at 36" to 38" as required by frost depth.

 

[alia176]

how were you able to work the wet cement so that you have a perfect level surface? Or does the surface not have to be perfect since you're going to put down a bed of mortar before the first course of block?

 

[Delancy]

I never saw a level footing when I worked as mason's laborer as a teen. Set up the corner guides with a line level, then adjust the first course level.

We use a laser, nowadays, but primarily to ensure elevations are correct to a benchmark, not necessarily to level for other trades.

Edited: @ PA Toyota.

Enjoy the dialogue and reason for continued thread participation, but if considering thread hacking, please advise and I'll delete posts.

 

[alia176]

Thanks, I was just curious. I'm going to sort of follow this thread for my own shop building this year and these simple questions help me understand the process better!

It's rather amazing to me that one can adjust the first course using the mortar bed, considering how much weight ends up on that block wall. That 1st layer of mortar bed is mighty strong, to say the least.

 

[PAToyota]

Not a problem to add to the discussion, Delancy!

Things have been at a standstill with the weather. If it gets above freezing, it's raining. So I've been working on other projects until things warm up again. March will be here before we know it.

I set where the top of the foundation should be and poured to that. A common way to mark is to pound rebar into the ground every so many feet - using a transit or level to make sure that the tops are where you want to set the top of the foundation - and then just pour to those. Or I have seen people use either a transit or laser level to check as they pour and use a rake to tamp the mortar around to get it reasonably level. But in any case, certainly not level in the sense of having a floor level or framing in a window level.

As Delancy notes, you make up the difference with mortar. A typical mortar joint is 3/8 inch. Now, you're not throwing down three to six inches of mortar to level things up! I'd say I got things probably within an inch to maybe an inch and a half at the greatest. As I set the first row of block, I'll run the mortar heavy where the foundation is low - maybe up to an inch or so. If things are out more than that, I can make up a bit more between the first and second course (or even the third course, if necessary) and I'll still be below grade so it won't show. This is another advantage of not filling the trench the whole way up to the adjacent surface for the foundation - then the block is all above grade and you'll see your odd mortar joints.

The mortar has a compressive strength of around 1800psi for Type S and 2500psi for Type M. So "extra" mortar in the joints isn't really making the wall weaker - you've got 3/8" of mortar between all your blocks anyway. The main issue is that it is difficult to lay a block on more than 3/8" of mortar because when it is wet the weight of the block will squish it out the sides. For the first course, though, you're not worried about it squishing out the sides because it's just on top of the foundation. So you can build up a little "platform" of thicker mortar on the foundation to support the block while the mortar dries.

 

[alia176]

Ok, got it.

When you did the concrete work, did you have to do anything to get rid of the trapped air?

 

[PAToyota]

No, not for something like this.

When you get into using concrete vibrators and such is when you're doing formed concrete - like a wall or pier or such - especially when you have a lot of reinforcing.

For the foundation, just pouring the concrete from the wheelbarrow (or from a concrete chute if you have a truck) is enough to make sure that the concrete fills up the space.

But in a wall form, where you have several feet for it to travel down and around a bunch of reinforcing then you can have issues with pockets.

 

[alia176]

Ahh, got it. Thanks.

 

[PAToyota]

There are times that you'd want to use a vibrator for concrete formwork for cosmetic reasons. Like for a concrete countertop. There you want to be absolutely sure that there are not going to be any voids.

But for something like a foundation, it isn't like you're going to have any big enough voids for it to be a structural problem and you're never going to see it anyway. Something like a floor isn't an issue because the surface is going to be exposed to finish it and any internal voids won't be big enough to be a problem.

There would be cases where you'd want to vibrate something like formed steps. Any voids won't be a structural problem, but you may have minor cosmetic voids against the form that will be visible when the forms are stripped. Most cases, all you need to do is use a rubber mallet along the form. In the case of the concrete countertops, they do use vibrators or something like a palm sander held against the form to vibrate it.

 

[PAToyota]

Well, the weather is slowly turning more favorable. This past weekend had nighttime temperatures above freezing for a couple days. Unfortunately, the first step was cleaning out the dirt that had fallen down into the trench on top of the footings. I had really wanted to get one course of block laid the whole way around and then cover that so that I wouldn't have that problem. Mother Nature didn't quite cooperate with that, though.

So I now have the back side corner set, one course set along the back wall, the front side corner set, and one course set along the side wall. Next possible warm weather is in a week, so I want to get the rest of the trenches cleaned out by then so that I can just concentrate on laying block.

With the corners set and the first courses laid out, things should go quicker to just fill in between corners.

 

[alia176]

You know, it'd be very helpful if you could just set a video camera on a tripod and give us a time lapse video! Just kidding.

 

[PAToyota]

Well, for the past two months it would have pretty much looked like this - just add snow, watch it melt, watch it rain, watch it dry off, add some more snow...

 

[PAToyota]

Well, they had been saying that this weekend would have overnight temperatures above freezing. Then it moved back to next week, then later next week, then next weekend... Now it is looking like the first week of April will have overnight temperatures above freezing...