I am building my own shop on weekends. I am building it out of a ICF material called Rastra.
I finally have the roof and the garage doors on and am in the process of installing a couple of windows. I decided I wanted to have concrete window sills. I made forms and poured them last weekend. The turned out fair, but have room for improvement.
To this point, I’ve only tackled concrete work that wasn’t going to be seen. These window sills were small enough I felt comfortable tackling them.
But I was hoping someone here could either describe or point me towards some information on what you need to look for in finishing concrete. How much to work it, how to know when not to work it, etc. I have no intentions of trying to become my own concrete guy for big pours. But I would like to be able to do a few more of these window sills or a door sill perhaps. Maybe a counter top on an outdoor barbeeque.
I attached a photo of my handy work. You can see the vertical edge suffers from some aggregate showing – any suggested fixes? I thought I gave the forms ample taps to get the concrete to settle…
Thanks in advance for your help.
Daen
Replies
Doode, with a back drop like that, who's gonna look at the sills?
My son makes concrete countertops and such, all I can say is there's a learning curve, you'll get better.
And, tapping isn't vibrating, and sometimes vibrating isn't vibrating...
just giving a bump and a howdy.
I went down to the lobby
To make a small call out.
A pretty dancing girl was there,
And she began to shout,
"Go on back to see the gypsy.
He can move you from the rear,
Drive you from your fear,
Bring you through the mirror.
He did it in Las Vegas,
And he can do it here."
At this point I'd think about what you can do after the fact. If you have some areas that kind of have that distressed look, then go with it.
After all, that is the beauty of concrete. I recently poured and finished a concrete walkway but I didn't want it to look new. So I acid etched it. I took a few applications of the acid with plenty of water to get it off but the results were worth it.
It took off the gray plastic looking cement and left exposed sand.
after you open it up like this you want to seal it well. I used a sealer that was silicone based so it didn't change the appearance. No gloss at all. But water beads right off of it.
You might try this. Make it look like you meant it to be that way.
One thing I remember about reading an article on concrete countertops. They vibrated the concrete by taking a rotary hammer drill and putting the bit on the form.
Edited 4/3/2009 8:35 pm ET by popawheelie
Cast then away from the building.
Make a form and cast them upside down.
Google concrete counters or give a shout out here to ponytail or waters.
Among others here they have done this type work.
I've cast maybe 100 sills all out of one mold... i've cast them as long as 8ft where they also act as the lintel/header for french door units directly below them... in these i use rebar
but... as was stated you want to cast them upside down... i use white portland and whit golf course sand (very white clean sand) and i use a crushed very light grey rock... almost white....
mine when cast look like polished limestone..
my mold is made out of 16ga sheet metal... it's 100" long and 12" wide (12" works for what i used them for) they are 3.5" thick with a 8" of flat on the top and then it tapers down to 3" on the front edge.... for water to run off... i set my doors or windows to the the edge of the 8" flat...
i cast them upside down... i have a movable block that i clamp in place to make the sill how long i need it... i wax the mold with automotive wax... I vibrate with recip saws... jig saws... or best thanks to another breaktimer a hammer drill...
I______/I kinda what my mold looks like the sides come up over 1.5" and then down 1" that lets my sheet metal mold sit on standard 2x4's which i have mounted on 3/4 plywood.. so if you follow the steet metal it's up 1" over 1.5" down 3.5" over 8" up at about 5 degrees for 4" then up 3" over 1.5" then down 1"...
my mix i use alot of portland... 1 part portland 2 parts sand 1 part rock this is a very heavy portland mix (you can go to 2 parts rock and it'd still be heavy on portland...) but with my mix you can have it much wetter and still be strong...
you can get it very smooth right out of the mold with this mix and alot of tapping and vibrating... OR you can make it look like a porous rock/coral with no vibrating just a few taps and leave the bubbles... nice natural stone look
i play in concrete just about everyday... so yell if i can help
P:)
got any pics of the limestone look..
I'd like to see thatAlso I've never done it, but from what I've read a lot of people use melamine or some other laminate for the upside down forms.
Edited 4/4/2009 2:28 pm ET by egdc
Thanks all for the input. I had someone else suggest casting them offsite... will have to try that next time.
My concrete mix - well not very scientific. A bag of premix from Home Dump and a couple extra handfuls of gray portland tossed in. I did throw in some rebar along each edge.
I had been looking for a used concrete vibrator off ebay or craigslist. But they keep going for more than I can justify spending. But I do have on hand sawsall, hammer drill, jigsaw, sanders. Sounds like any of those might do the trick also.
I would like to hear a little more on people's mix formulas. And also a little more on the actual techniques of finishing.
The pictures I posted actually make it look a little worse than it is. My profile is similar to the other one described above. Mine is 13 inches wide (10 inch wall plus a 2x spacer on each side). It is 3 inches on the inside, runs flat to the mid-plane of the wall, then tapers to 2.5 inches on the outside. I cut a piece of plywood to this profile that I screeded along my forms when I poured. This was part of the challenge in forming these up - the screed kept grabbing hold or agregate and pulling it up.
I had covered my forms with some used motor oil as a release, but as you could see in the pics, that vertical edge still had a little sticking.
Getting a sheet metal form bent up shouldn't be a problem for me. I know and work with folks that do that sort of thing.
Thanks again and looking forward to more input.
DC
check out this thread:http://forums.taunton.com/tp-breaktime/messages/?msg=101058.0
check harbor frieght for a vibrator,concrete......................YOU ONLY NEED TWO TOOLS IN LIFE - WD-40 AND DUCT TAPE. IF IT DOESN'TMOVE AND SHOULD, USE THE WD-40. IF IT SHOULDN'T MOVE AND DOES, USE THEDUCT TAPE.
I've used sheet metal...it's ok smooth... but the smoothest i've gotten is using lexan/plexiglass... i get the sign faces that have been removed from large signs from the sign shop... they are all headed to the dumpster... i use the back side that has not been exposed to the sun or painted... with this material i get a VERY slick finish that people think i polished ....
LOL me pictures... i know i should but i just don't take many.... I usually wait for someone else from breaktime to stop by and take pictures and post em for me... <g>
:)p
oh yeah i left out while the concrete is in the mold... on the outside edge bottom about 1/2" back from the front edge i put a small groove maybe 1/8" deep on what will be the bottom side...installed.... i leave mine proud from the finished outside wall about 1 1/4" this "groove" acts as a drip edge making water drop off vs try'n to run under your sill... also when i place mine in a bed of mortar... even with the cast in place slope i still put just a little slope to the outside on the whole thing...
Here are a few shots of the installed windows on the concrete sill.
i think they look good... nice work... they go very well with what you have...
I'm a huge fan of concrete... i mean who else other than God can make a stone?
<g> P
Daen,Congratulations on your achievements so far. I have sent an e-mail to your profiled AD, but I don't know if you will see it or not. I would like to help with a few tips, but am reluctant to go into too much detail in a post. Up to you if you want to take it further.My AD is <[email protected]>Lapun.
Edited 4/8/2009 6:48 am ET by Lapun
Daen,your server has determined that I am an undesirable alien, and all efforts to email material on this thread are being deleted.I would not like to think that there is any other reason for this result.I must leave any further action entirely dependent upon your initiative. A disappointed Lapun.
Daen,
My apologies to AT&T for my harsh judgment of their apparent deletion of my emails to you, although I still feel there is a retardant in there somewhere.A much happier Lapun.
Be aware that you can take a grinder to concrete to remove flashing and other errors. It works really well on newer concrete.
nice doors... I need to replace my garage door this spring and am looking for suggestions. I have fancied the idea of building my own but do not know if that is practical.
I refuse to accept that there are limitations to what we can accomplish. Pete Draganic
Take life as a test and shoot for a better score each day. Matt Garcia
Pete, it isn't hard to build garage doors but you can always buy something cheaper if that is the goal. If you want the carriage house style doors, you can probably build cheaper than buy.
Rich
To refinish your sill all youll need is a bag of plastic cement (with no added sand)also Thinset will work. You mix it to the consistency of mayonnaise and putty it on like drywall mud. With a paint brush and water smooth it out. The hard part is to keep it from checking and cracking. You must soak the surface real good so it does not suck water out of the mix. Do it when it is cool and windless, direct sunlight will cause a lot of cracks. Practice first on one of the extra pieces of blocks. Different brands will produce different colors or texture.
Then post pictures of your success or failure.
Edited 4/10/2009 12:34 pm by Sungod
Without reading the other responses... You can use a rotary hammer, air chisel, or other similar tool as a vibrator. Use small aggregate. If you use white cement and white sand you can actually cast something that looks pretty attractive.
PS - not to drag the discussion off on a tangent but,,, What is that rasta block made out of? It looks like regular cinder block...
IIRC it is made out of recycled plastics processed into a slurry of cement. http://en.wikipedia.org/wiki/Rastra I think there may be some versions made with wood fiber as well.
They can't get your Goat if you don't tell them where it is hidden.
Rastra has a pretty good web site...
http://www.rastra.com
Basically they break styrofoam into pellets and use that as the aggragate to mix with cement.
The blocks are 15 inches tall, 90 inches long, and come in widths of 8,10,12 and 14 inches. 10 and 12 are the most common. The 10" block gives an R value in the 22-23 range. The 12" block is somewhere in the mid 30s.
You stack it and hold it in place with expanding foam glue until you grout the wall. The block has grout cells on 15" centers. You can combine blocks horizontally and vetically and cells line up. The 15" dimension supposedly is a fallback to the European (metric) origins of the product. Sure wish it was 16". That would allow the use of some joist hangers Simpson and others offer that get burried right into the concrete eliminating the need for ledgers. The thought of trimming all my subfloor sheets to 45x90 inches as well as all the products designed to fit in a 16" joist bay.... So I installed ledgers and standard joist hangers to them.
Termites don't like it. Also, when you grout the cement becomes monolythic with the block. I have read were when using the all-styrofoam ICFs, the concrete can shrink from the foam and leave a gap for the bugs to travel through. Don't have any personal data or observation to back that up though.
I cut it with a hand saw. It has big teeth like an old lumberjack's saw. I can cut through a block in 10 or 12 strokes. The 10" blocks weigh about 120. The 12" blocks run just under 150. I have a skid steer loader that I used to lift the blocks. I stacked each block individually. I have read where some people glue a section together laying down and then stand it up.
The glue holds pretty well. I had a bad wind storm knock a section of wall down before I had it grouted. In many places the blocks broke instead of the glue joint. If you do manage to break a block, just use the foam glue and put it back together.
On the down side it is expensive up front. I don't build for a living so dont have any hard figures. But my salesman thinks the cost of the wall runs about 125% of a 2x6 wall with stucco. A big part of that calculation comes in the saved labor. When you are done stacking the wall, you have framed, sheathed, insulated, scratch and brown coated the exterior, and drywalled the interior. You can make your own judgements about the validity of the comparison.
My intention for the interior is to apply smooth stucco and then when I texture the interior partition walls I'll just continue the texture onto the stucco. Once painted you can't tell the difference.
As for hanging things, well sort of like living in an old brick building. You need to plan ahead for heavy things like kitchen cabinets and get nailers grouted into the walls. Although with some of the great concrete anchors available today, you can generally get something attached after the fact.
Hope this gives a little sense of the product from an owner/builder's point of view.
DC
Edited 4/28/2009 8:57 pm by daen
Thanks for the first hand explanation. Sounds like you are gonna have a very snug shop/garage.
RE concrete, if you have any specific Qs, ask away. I have a fair amount of experience with it, although not so much with casting things like your sills. Further, on the concrete topic, we (collectively) have a wealth of knowledge on the topic.