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This is just below the flooring surface in a kitchen and inches from the back door out onto the garden. Camera is looking down - it's an inch and a half long. The 1971 concrete lintel has five of these anchor points, and three don't have wood in anymore. The hole is deeper front to back underneath that it is at the surface.

I think I have to soak some wood that's roughly the right shape then use a clamp or a vice to compress the fat end. Then place it in the hole. Then let it expand to fill the hidden part of the hole, then dry, then shave off the excess somehow.

There could be an alternative using two shaved pieces that can be epoxied into place.

And there could be an alternative with some modern liquidy stuff that sets in place and can take a screw later.

The wooden layer on top of this lintel/anchor would be 1/4" (6mm), and that'd make the subfloor level enough to take laminate/etc for completion of the flooring to the back door.

Ideas?

Anchor without wood in place

Selected Answer:

enter image description here

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  • 2
    What are the wooden anchors for? Are they just easy places to use nails/screws to hold something down?
    – crip659
    Jun 28 at 16:50
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    Can you also provide a picture of one with wood in it? Soaking wood will make it expand, not compress, so I think your soaking idea is right out. What is this supposed to support and how? Some sort of overview image would be really helpful.
    – FreeMan
    Jun 28 at 16:51
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    Is there a reason you want to fill that with wood? If you're putting a board over the top of it, why do you even care? And if you do, why not use a little concrete? If you want something in the lintel that'll take a screw, drill a hole in the concrete wherever you want and put a Rawlplug in.
    – Graham
    Jun 29 at 8:49
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    I would love a photo with more context. While I answered your narrowly-scoped question I still have no idea as to the purpose of this thing.
    – isherwood
    Jun 29 at 13:06
  • 2
    Do you mean door threshold? Jun 29 at 18:43

4 Answers 4

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Three pieces, connected with wood glue.

ELEVATION (SIDE) VIEW
         ___ __ ___
        /   |  |   \
       /    |  |    \
      /_____|__|_____\

You could make the center one a slight wedge to tighten things up.

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Is this really a lintel ? That would be spanning over a window or door, not in the floor.

The old wood is gone because it failed over the course of 50 years. Wood doesn't survive being encased on 5 sides by concrete, and presumably it was cast in place so there's no moisture barrier.

I'd simply clean it out, then fill the hole with mortar or concrete, and cover the whole area in levelling compound to support your subfloor.

If you want to anchor something to the floor, use a concrete drill, and ramset bolts or an epoxy compound to secure a metal fastener in each hole.

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    Or, cast (appropriate) concrete anchors in place when filling in the holes and skip the drilling. Could use a temporary support board and screws to position them. I will second the comments about wood in concrete; need a vapor barrier and to break the path of capillary action! Jun 29 at 18:39
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I would consider putting two saw cuts into the end of the wood plank that fits in the hole - just slightly less deep than the hole.

Then make two wedges that will expand the end as the plank gets hammered into that hole - the wedges are sitting on the back of that hole so as the plank comes in the cuts get forced open locking it into place - and the plank is all one piece.

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    This is similar to my suggestion, but upside down. One drawback is that the wedges must be precisely fit in advance since there's no control over the wedge position. Another is that the block is likely to split, possibly twice. Yet another is that by virtue of the spreading action the base (top side) will no longer be flat.
    – isherwood
    Jun 29 at 13:05
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And there could be an alternate with some modern liquidy stuff that sets in place and can take a screw later.

It's called epoxy. Some of it will take screws quite nicely, other types may not. However, since you're laying a 1/4" subfloor over this then putting a laminate floor on top of that, why would you need a screw precisely in this location?

Why would you be screwing down your subfloor in the first place? I'd imagine you'll be holding the subfloor down to the concrete with adhesive and it should hold just as nicely to epoxy as it will to concrete. Even if it doesn't the very small area where this is missing won't make a difference in the hold of an entire sheet of subflooring anyway.

Every laminate flooring material I'm aware of either glues down to the subfloor or floats on it, therefore there would be no screws at this point either. The "take a screw later" concept is a red-herring or there's something else you're not telling us.

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  • [something else you're not telling us] The remaining piece of subfloor is a standard door with by four inches. Depth 1/4" (6mm). The door was replaced. Was original wood, and is now is PVC double glazed (and opens out). The door frame has moved that four inches further out and there was room to do so. Including the fitting firm noting the position of the cavity between the red bricks and the UK's historical lightweight concrete blocks that guides vapor somehow. The piece of wood is slim, under the laminate. I'd have to glue it, or screw it to hold it firm.
    – paul_h
    Jul 2 at 15:54
  • Still a little lost, TBH. But, it seems you've come up with a solution, so if it works for you, it works for us.
    – FreeMan
    Jul 7 at 11:55

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