Cardiffbloke
Member
- Messages
- 30
- Location
- Cardiff
Hi There, amazing site, cant get off it!! 
... Ok, my first post (first of many, no doubt). Just moved into an Edwardian Semi in Cardiff. Bit of damp in ground floor parlour bay window area (picked up on survey). So on investigation lifted a few floorboards to reveal rotting joist ends and very damp main walls on the interior (up to the DPC only thank God!), dwarf walls (which were sat right next to the interior of the main walls), and rotten wooden joist supports (the 4 by 1 in flat planks sat on the dwarf walls). Stripped the whole lot out, including the fireplace bed (which was dripping) and found myself left with 4 walls and a clay floor!
It was clear that the ventilation holes were completely inadequate and actually only just below the level of the floor (in line with the joists). The dwarf walls were constructed right next to the building walls and all the dampness coming in through the walls below the DPC and the ground below was wicking up and into the joists. Nearly every one was 3/4 shot through. So... rebuilt vents so that they now vent below the joists. Rebuilt dwarf walls 1 to 2 in away from all exterior walls, creating a space for ventilation. Placed DPC along all supporting surfaces and replaced all woodwork with tanalised timber. Re-built fireplace bed in readiness for a new coal/wood open fire and generally tidied the whole floor up.
Ok, so what is my Q? I want to replace the floorboards but before i do i want to place some insulation under them and between the joists. I have bought some rolls of 150mm "Space Blanket" by Knauf. The sort you insulate lofts with. My friend told me his father did it in a similar house and it made the room really warm but didnt compromise the suspended floor ventilation as it maintained the space beneath the joists for ventilation purposes. I would not take it all the way to the walls but maintain the 2 in ventilation gap. Which should provide for the air to flow to the fire. But i have read worrying posts by learned people on here that talk about the foil surface of the insulation forming condensation. I aim to put the blanket between the joists shiny (foil) side down (the opposite to how it is in a loft) so it is exposed to the air and not below the floorboards.... i'm rambling.... you know what i mean!
am i heading for disaster!?
Howard[/i]
... Ok, my first post (first of many, no doubt). Just moved into an Edwardian Semi in Cardiff. Bit of damp in ground floor parlour bay window area (picked up on survey). So on investigation lifted a few floorboards to reveal rotting joist ends and very damp main walls on the interior (up to the DPC only thank God!), dwarf walls (which were sat right next to the interior of the main walls), and rotten wooden joist supports (the 4 by 1 in flat planks sat on the dwarf walls). Stripped the whole lot out, including the fireplace bed (which was dripping) and found myself left with 4 walls and a clay floor!It was clear that the ventilation holes were completely inadequate and actually only just below the level of the floor (in line with the joists). The dwarf walls were constructed right next to the building walls and all the dampness coming in through the walls below the DPC and the ground below was wicking up and into the joists. Nearly every one was 3/4 shot through. So... rebuilt vents so that they now vent below the joists. Rebuilt dwarf walls 1 to 2 in away from all exterior walls, creating a space for ventilation. Placed DPC along all supporting surfaces and replaced all woodwork with tanalised timber. Re-built fireplace bed in readiness for a new coal/wood open fire and generally tidied the whole floor up.
Ok, so what is my Q? I want to replace the floorboards but before i do i want to place some insulation under them and between the joists. I have bought some rolls of 150mm "Space Blanket" by Knauf. The sort you insulate lofts with. My friend told me his father did it in a similar house and it made the room really warm but didnt compromise the suspended floor ventilation as it maintained the space beneath the joists for ventilation purposes. I would not take it all the way to the walls but maintain the 2 in ventilation gap. Which should provide for the air to flow to the fire. But i have read worrying posts by learned people on here that talk about the foil surface of the insulation forming condensation. I aim to put the blanket between the joists shiny (foil) side down (the opposite to how it is in a loft) so it is exposed to the air and not below the floorboards.... i'm rambling.... you know what i mean!
am i heading for disaster!?
Howard[/i]