Repointing powdery mortar

Discussion in 'Plastering and Rendering' started by curium, 15 Oct 2021.

  1. curium

    curium

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    Hi All,

    I live in a 80+ year old semi-detached house with solid brick walls. Two skins with no cavity.

    I've had to get the flooring up due to issues with the gas and water supply.

    I plan on replacing the flooring with T&G chipboard to eliminate gaps as we get mice coming in.

    While I've got the floor up I'm considering filling in many gaps in the brickwork below floor level to reduce the opportunities for mice.

    The existing mortar is very powdery and easily removed.

    I'm looking for advice on stabilising it before filling the gaps with a sand/cement/lime mix.

    I'm also looking for advice on the ratio of sand/cement/lime and what I should be asking for in the builders merchant to use as 'lime'. I know nothing about lime but have read repeatedly that it should be used in a property of this age.

    Many thanks
     
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  3. tell80

    tell80

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    waste of time reeplacing t&gfloor boads with chipboard, the mice usualy come from behind the skirtings at floor edge.
    same with pointing below floor level, the mice dont come through the walls
     
  4. curium

    curium

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    Well the current floor has had to be cut out to access services underneath. The previous owners had glued plywood to the floorboards and then glued vinyl tiles on top so there was no option but to cut it out.
    Given the above, t&g cupboard seems a sensible replacement.

    In your experience how do mice enter the building if not via gaps in the walls? I’ve purchased mesh for the air-bricks.
     
  5. tell80

    tell80

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    In a 80rr old house Its typical to lift a few t&g floorboards for access to services, or to go under the floor.
    Pointing the beds and perps will do nothing for stopping mice, ive never heard of them burrow through bricks and mortar.theres openings such as around pipesall overhouse walls.on youtube i watched a mouse entering under a door.
     
  6. opps

    opps

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    They may be entering the foundations from many routes, eg your airbricks, gaps around service pipes or gaps in the party wall (where there are missing bricks).

    The walls are double skin, unless you can see evidence of the mortar missing all the way through 9 inches of brick, I might be inclined to ignore the pointing.

    Possible routes from the foundations? Kitchens often have massive gaps in the flooring under the units. Particularly where they meet the walls. Electricity and gas meters under the stairs.

    In short, I am suggesting that you might be better off blocking access in to your living area that trying to block access to the foundations per se (unless you rip ALL of the downstairs flooring up).

    BTW, I had a customer in Chiswick who paid tens of thousands to have the foundations backfilled with concrete to get rid of rats. They never entered the living area but she had a few nests in the foundations. It freaked her out so much that she put heavy objects on the loo seats on the ground and first floor and would only pee in the loo on the second floor.
     
  7. curium

    curium

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    @opps I've had friends who have had rodent damage to the electric cables which run in the underfloor space so I'd rather keep them out if I can.
     
  8. opps

    opps

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    Good point. Rats need to chew "stuff" to wear their front teeth down. AFAIK that is far more common in loft and floor/ceiling spaces though.

    I don't blame you for wanting to make the foundations rodent proof but if you really want to do that, you may need to crawl from the accessible areas to, for example, under the kitchen.

    A rat is not going to be able to chew, and then fit through, the regular mortar gaps between bricks. I honestly cannot imagine a mouse being bothered to.

    If you do find any holes, then wirewool stuffed into them will be more effective. It grates on the mouse's nose and hurts it. But again, do not ignore airbrick holes (you can fit meshes over them).

    Apropos, lime mix in the mortar. Why? Do you understand how caustic lime is? Regular sand and cement is absolutely fine for pointing in the foundations. In practice it is fine for exterior pointing too, so long as enough old mortar is raked out.
     
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