Know-It-All
· Stockholms län
· 822 posts
Hello, I have had a hole cut for a staircase in the hallway's ceiling up to the attic and have furnished it. The ceiling consists of concrete slabs. The staircase is now installed, and I need to seal the hole where our attic ladder (hatch with folding ladder) used to be. The hole is approximately 50x110 cm. Since the hole cutting is an intervention in a load-bearing structure, I have submitted a building notification for this. In our construction drawing that the building permit unit required for this intervention, the hole should be sealed with coarse concrete. I have now acquired coarse concrete and rebar but am now considering the following:
1: How should I handle the ceiling below where the hatch was, can I put up a board with joists underneath and prop it up? Can I then cast a little at a time so that it doesn’t become too heavy?
2: How do you finish the ceiling to get a nice surface similar to the one surrounding it?
3: How long does it take for the concrete to cure sufficiently for me to lay flooring over it? The floor above the concrete slabs consists of foam boards with floor chipboard. Over this, laminate flooring will be laid. The concrete cassettes in the slabs are about 20 cm thick.
Grateful for suggestions and ideas on how to proceed.
1: How should I handle the ceiling below where the hatch was, can I put up a board with joists underneath and prop it up? Can I then cast a little at a time so that it doesn’t become too heavy?
2: How do you finish the ceiling to get a nice surface similar to the one surrounding it?
3: How long does it take for the concrete to cure sufficiently for me to lay flooring over it? The floor above the concrete slabs consists of foam boards with floor chipboard. Over this, laminate flooring will be laid. The concrete cassettes in the slabs are about 20 cm thick.
Grateful for suggestions and ideas on how to proceed.
I would get a thick plywood board and brace it against the floor underneath with some form of support. It might be a good idea to screw some studs to reinforce the board so it doesn't bend.
Drill the rebar into what you will cast and do everything at once.
Rent a concrete vibrator to make it completely homogeneous without air bubbles.
Are the ceilings plastered in the rest of the house or what do they look like?
Expect it to take a couple of weeks before it is dry enough to be built in with Styrofoam and other materials.
Fredrik
Drill the rebar into what you will cast and do everything at once.
Rent a concrete vibrator to make it completely homogeneous without air bubbles.
Are the ceilings plastered in the rest of the house or what do they look like?
Expect it to take a couple of weeks before it is dry enough to be built in with Styrofoam and other materials.
Fredrik
Know-It-All
· Stockholms län
· 822 posts
Yes, the ceilings are plastered. How do you then plaster the cast surface, should I put something at the bottom closest to the plywood so to speak?
Know-It-All
· Stockholms län
· 822 posts
OK! Thank you for the answers.
Keep in mind to stabilize the formwork, as concrete is heavy and there will be significant forces from the vibrator. If you place 4 - 6 pillars, connect them sideways as well to prevent them from buckling when you vibrate.
Also, try to seal the formwork, as there is quite a bit of dirty water in concrete. For example, a latex sealant is easy to carve away later if needed.
Also, try to seal the formwork, as there is quite a bit of dirty water in concrete. For example, a latex sealant is easy to carve away later if needed.
And pre-water the surface!
When the hole is so small, fast-setting concrete might be an option, more expensive but faster.
When the hole is so small, fast-setting concrete might be an option, more expensive but faster.