cavity wall

  1. P

    Would building a batton wall on the inner side of an exterior cavity wall cause any problems?

    Hiya, thank you for reading this :-) The details are: the house is a 1987 build with: Red brick outer skin, Cavity (I don't have any more info about the cavity at the moment as all our stuff is in storage), Thermalite blocks, Thick plaster (12mm approx), And a skim coat of plaster. On top of...
  2. JamieDIYs

    Lime constructed house with cavity wall… can you insulate

    Hi all, just wondering what people’s thoughts are on cavity wall insulation on a 1910’s built house constructed with lime mortar. I’ve read a couple of horror stories online about people installing modern cavity wall insulation into a period property which subsequently caused a multitude of damp...
  3. N

    Wall design for outbuilding

    Hello all :) Never built anything big before. I'm want to build a masonry 15m2 outbuilding as a gym. I want to use the building all year round and I can imagine a lot of body heat being generated. I plan to have an electric heater too for winter. I have two wall designs I would appreciate...
  4. C

    Air bricks above floor level feeding into cavity. Why?

    I've recently purchased an '80s semi-detached bungalow and currently in the process of renovation. Originally, the property was heated via a warm air system and water heater, but this was replaced ~10 years ago with a Combi Boiler CH/HW system. In the kitchen there is a cupboard in which was...
  5. P

    How to Cut Small Access Door in 300mm Cavity Wall

    Please can i get some advice how to cut a small access door in this wall. The photo shows the back of my house which has a crawl space below the airbricks. I want to cut an access hole approx 50cm X 70cm to the crawl space, the proposed hole is marked with green colour. The wall is two skins...
  6. S

    Cavity wall clearing

    Does anyone have any expericence of cavity wall clearing I have found the cavity walls have quite a bit of sand in them. The sand bridges the DPC and in some cases goes above 400mm above DPC. Aslo as you go down the wall it turns solid mortar. I was thinking of trying to get a rotary mutitool...
  7. Rob broom

    Expanded galvanised mesh in blockwork -advice please!

    Hi all! I am currently building a 2 story extension. It’s a cavity wall, with 7n dense blocks outer leaf and a 3.6n aerated blocks for the inner leaf. What are peoples thoughts on expanded galvanised mesh? Do I need to use it in the blockwork? Is it vital? Is it overkill? Should I use it on...
  8. mariogg

    Cavity trays on party wall & lead flashing

    Wondering if anyone can help, looking after some guidance please. I’m doing a loft conversion and currently reinstating the party wall edges. I had an issue with leaks prior to this and I believe it was due to having old concrete tiles on angle, without any lead flashing. I’ve attached a...
  9. Rob broom

    Adding an Extension - External Walls becoming internal walls.

    Hi guys, A bit of advice again please! Please see the attached image. Question 1: Is it ok to connect a new wall to an existing wall and have the outer leaf's flush? In the picture, the red bricks are the outer leaf of the existing cavity wall, and the grey and green blocks will be the new...
  10. M

    Bricklaying approaches

    Hi Just wondering if someone could give me some advice on how brick layers in the construction industry go about building a cavity wall. What I have been taught is to rack back corners then use a string line to fill in the middle of the wall with bricks. However I've seen a few different...
  11. Rufio123

    Forgot to use 'wall starter' ties on inner leaf.

    I have been working on a wall in my kitchen underneath a window. The wall underneath and to the right of the window only had a single skin wall where it then meets a solid wall of the original house. To the left of the window is a complete cavity wall and I have extended it to underneath the...
  12. P


    Hi all, I wonder if anyone can advise. We bought a 1930s property and decided to sleeve off/bridge the airbricks that were already there to ventilate the underfloor. I heard that the cavities need ventilation too? Will bridging the airbricks afect the cavities? We are planning on installing...
  13. D

    Expanding Foam in Cavity Wall Issue

    I am a landlord and my tenants experienced issues with damp on the inside of a bay window and it didn't seem like there was an issue with condensation or ventilation (as is usually the case). I noticed a crack where the bay window render meets the brickwork on the outside of the house and...
  14. G

    Soil stack

    Hi all Need to gain 20 mm height on soil stack,the point where the soil pipe exits the building,I understand water doesn't run up hill only option I seen to have is relocate exit on gable end and bring around corner, completely out the way.I would also run the two external waste...
  15. G

    Hight of walls for lintel

    Hi guys currently self building single storey extension,all great so far blockwork up cavity 100mm,minor issue I need to gain 100mm in height for ig lintel Concrete block external toplight internal Best options 100mm coursing blocks all the way around ? Or a cheaper way of cutting a few...
  16. G

    Cavity fill

    Hi my cavity walls fall half a metre below ground,just wondering why a weak semi dry mix is required,I understand for the walls not to cave in,but why a weak mix,couldn't I over order on c25 mix for the floor slab and fill cavity with this,save loads of time.. Thanks
  17. S

    Stone wall cavity closer

    Hi, I would like a view on how best to close the cavities around window and door openings. The wall is 7N blockwork on the internal leaf and rough stone on the outer, which results in a very undulating cavity size. I have 80mm tongue and groove insulation in a 150mm cavity. The stone is at...
  18. J

    Confused about what to do with plaster

    I am buying a detached house, circa 1911 to 1926 (not on the 1911 OS map, is on the 1926). Survey identifies empty cavity wall (rather than solid wall) original plaster internally and original lath ceilings. It suggests the exterior render is original, looks ok, however has some loose sounding...
  19. T

    50mm Rockwool in cavity wall not 100mm

    Hi lads Can I use 50mm or 75mm in cavity walling and not use the 100mm, its a small music room extension and trying to cut back in costs? 100mm fully fills the cavity I know but would it be k to not totally fill it. Thanks S
  20. T

    Trench foundation at boundary? Cavity wall position

    I’m building a rear extension on my end of terrace bungalow, my Architect has specified a 600mm x 1000mm concrete foundation. At the adjoining boundary to next door we have a concrete post fence, the 150mm “toe” of foundation on that side of the 300mm cavity wall will need to go slightly past...