Progressing a project to generally improve the floor in the lounge/diner. Found loads of problems, but one I thought I'd seek some advice over.
as I've written loads, I thought I'd best come back to the top and write a little summary... the ventilation void under a chipboard floor is tiny!
As part of the works I was planning to insulate between the joists using earth/mineral wool on wire mesh. Problem I've found is the room is made of two halves of sub floor. The older part is 1890s with a 1960s extension (might have been lots of the 1890s stuff replaced by the looks of it). It has a reasonable void of about 125/150mm. The 1980s extension is somewhat different. it has a concrete subfloor with a tiny 50mm void. I'm thinking that it is already somewhat dodgy! The void is 125mm if you go off the underside of the chipboard. I was planning to use 50mm deep mineral wool as the joists are only 75mm, but that'll make my tiny void pretty much non-existent. so now I'm thinking to leave it as is! can't see any damp problems in it yet, but been focusing on the older part (and its many problems) till I noted this.
The ventilation is a bit odd too. 3 very long vents under a conservatory concrete floor (all about 3m long) into the 1980s part. a single 120mm x 150mm vent brick into the older part. the larger void carries on into the hall which opens into other rooms of the bungalow which are also vented. the other rooms have a seemingly sensible number of vents. had most of those floors up and insulated over the previous years. I seem to do a room per December...
any advice to be offered? I suspect the answer will be get someone in to take up the floor, dig down to a sensible void size and redo to probs current regs? leave as is, is probably asking for some problem to develop at some point down there. though has been there for 30 years now without issue?
for anyone with time on their hands, the other problems I've found (and working through fixing) are...
1) more deflection in the floor than I'd like in places. See below
2) long unsupported joist spans (2.5m on 75mm joists at 300mm spacing?)
3) a somewhat weakened joist right in the middle where floor boards meet chipboard. seems to have been from several things, including notching (with whatever it was notched for now gone), the long unsupported span. a big crack in it (at the top), one end not really supported as the wall plate at that end had rotted. and maybe some heat damage from being beside 2 badly lagged 22mm heating pipes.
4) a rotted wall plate. suspect it was from a leaking heating pipe at some point in the past. fixing this was tonight's activity.
5) No noggins under the 18mm butt jointed chipboard edges.
6) 22mm heating pipes with occasional bits of very thin pipe lagging.
7) the join of voids is cluttered and must have poor air flow. in its space are the 2 22mm pipes, which are over the old wall (from the 1960s extension, wall above now gone) foundation and immediately beside that knackered joist. and a wall plate (the 1980s extension has joists at 90 degrees to the older bit). between it all it looks to be doing a good job of blocking most of the airflow. will do an even better job when I put 25mm walled lagging on those pipes... planning to make some holes in the foundation (as its not now a foundation for anything) so the air can flow under all the obstruction.
8) an interesting bodge repair for that rotted wall plate. a new multi part wall plate (3 separate bits of timber) appeared to be placed directly on the sand/rubble subfloor. it was actually sitting on a bit of DPC the same width as the wall plate. the build up of dust and other crud over the years had buried the DPC though... it had some little 40mm square legs going up to the underside of the joists, though about 2mm short of actually being supportive. somewhat amazed that timber hadn't rotted at all from sitting pretty much in the dirt for at least the 13 years we've been here. suspect it was bodged by two owners previous... seems they were like that.
9) the only airbrick in the older void was partly blocked by that rotted wall plate, though the bit by the vent was fine. was the other end by the rad pipes that was rotted. nice steady breeze was coming in through it though and it was a still evening out.
10) the airbrick has a metal grill which has rusted away at the bottom. nice vermin entrance provided!
11) the channel through the wall was partly blocked by soil/dust. guessing it had either washed in (see below) or been blown in over the years and built up behind the wall plate.
12) the GL outside of that airbrick has been generously raised by the builders of next doors garden wall to be level with the bottom of the vent. said wall is also about 10" from the house wall, so access is nigh on impossible!
13) lots of loose floor boards which haven't helped with wear and tear on the carpet underlay. well knackered in places where the boards move and therefore rub.
14) there is another dodgy ground level wall plate on the opposite side of the room. haven't pulled the floor boards up that far yet to see why that is there..
15) some black pvc sheaved twin and earth. rest of the house has grey pvc from, I presume some past rewriting, so why is this bit left behind?
16) the batteries on my cordless screwdriver are 6 years old and don't seem to hold charge very well any more...
probably a few others I've forgotten too.
17) did miss one, so an edit.... probably need to add another airbrick or two for the old part of the room, though I've only got one external wall to work with and most of that is inaccessible due to next door's garden wall.
well done if you read all the way down here
steve
as I've written loads, I thought I'd best come back to the top and write a little summary... the ventilation void under a chipboard floor is tiny!
As part of the works I was planning to insulate between the joists using earth/mineral wool on wire mesh. Problem I've found is the room is made of two halves of sub floor. The older part is 1890s with a 1960s extension (might have been lots of the 1890s stuff replaced by the looks of it). It has a reasonable void of about 125/150mm. The 1980s extension is somewhat different. it has a concrete subfloor with a tiny 50mm void. I'm thinking that it is already somewhat dodgy! The void is 125mm if you go off the underside of the chipboard. I was planning to use 50mm deep mineral wool as the joists are only 75mm, but that'll make my tiny void pretty much non-existent. so now I'm thinking to leave it as is! can't see any damp problems in it yet, but been focusing on the older part (and its many problems) till I noted this.
The ventilation is a bit odd too. 3 very long vents under a conservatory concrete floor (all about 3m long) into the 1980s part. a single 120mm x 150mm vent brick into the older part. the larger void carries on into the hall which opens into other rooms of the bungalow which are also vented. the other rooms have a seemingly sensible number of vents. had most of those floors up and insulated over the previous years. I seem to do a room per December...
any advice to be offered? I suspect the answer will be get someone in to take up the floor, dig down to a sensible void size and redo to probs current regs? leave as is, is probably asking for some problem to develop at some point down there. though has been there for 30 years now without issue?
for anyone with time on their hands, the other problems I've found (and working through fixing) are...
1) more deflection in the floor than I'd like in places. See below
2) long unsupported joist spans (2.5m on 75mm joists at 300mm spacing?)
3) a somewhat weakened joist right in the middle where floor boards meet chipboard. seems to have been from several things, including notching (with whatever it was notched for now gone), the long unsupported span. a big crack in it (at the top), one end not really supported as the wall plate at that end had rotted. and maybe some heat damage from being beside 2 badly lagged 22mm heating pipes.
4) a rotted wall plate. suspect it was from a leaking heating pipe at some point in the past. fixing this was tonight's activity.
5) No noggins under the 18mm butt jointed chipboard edges.
6) 22mm heating pipes with occasional bits of very thin pipe lagging.
7) the join of voids is cluttered and must have poor air flow. in its space are the 2 22mm pipes, which are over the old wall (from the 1960s extension, wall above now gone) foundation and immediately beside that knackered joist. and a wall plate (the 1980s extension has joists at 90 degrees to the older bit). between it all it looks to be doing a good job of blocking most of the airflow. will do an even better job when I put 25mm walled lagging on those pipes... planning to make some holes in the foundation (as its not now a foundation for anything) so the air can flow under all the obstruction.
8) an interesting bodge repair for that rotted wall plate. a new multi part wall plate (3 separate bits of timber) appeared to be placed directly on the sand/rubble subfloor. it was actually sitting on a bit of DPC the same width as the wall plate. the build up of dust and other crud over the years had buried the DPC though... it had some little 40mm square legs going up to the underside of the joists, though about 2mm short of actually being supportive. somewhat amazed that timber hadn't rotted at all from sitting pretty much in the dirt for at least the 13 years we've been here. suspect it was bodged by two owners previous... seems they were like that.
9) the only airbrick in the older void was partly blocked by that rotted wall plate, though the bit by the vent was fine. was the other end by the rad pipes that was rotted. nice steady breeze was coming in through it though and it was a still evening out.
10) the airbrick has a metal grill which has rusted away at the bottom. nice vermin entrance provided!
11) the channel through the wall was partly blocked by soil/dust. guessing it had either washed in (see below) or been blown in over the years and built up behind the wall plate.
12) the GL outside of that airbrick has been generously raised by the builders of next doors garden wall to be level with the bottom of the vent. said wall is also about 10" from the house wall, so access is nigh on impossible!
13) lots of loose floor boards which haven't helped with wear and tear on the carpet underlay. well knackered in places where the boards move and therefore rub.
14) there is another dodgy ground level wall plate on the opposite side of the room. haven't pulled the floor boards up that far yet to see why that is there..
15) some black pvc sheaved twin and earth. rest of the house has grey pvc from, I presume some past rewriting, so why is this bit left behind?
16) the batteries on my cordless screwdriver are 6 years old and don't seem to hold charge very well any more...
probably a few others I've forgotten too.
17) did miss one, so an edit.... probably need to add another airbrick or two for the old part of the room, though I've only got one external wall to work with and most of that is inaccessible due to next door's garden wall.
well done if you read all the way down here
steve
