Rate my sub-floor!! (and can you help me insulate it?!)

[larry]

Hi everybody, I hope as ever I can get some good advice here.

 

I've been working through the upstairs of our house doing wood fibre insulation on our walls and it's all gone well. Progress is slow but I have two rooms basically complete now.

 

Today marks Day 1 of trying to tackle the downstairs...

 

The plan was to do the walls with a parge coat, battens, wood fibre boards and then the floor with Rookwool sitting on some kind of membrane between the joists. I've already got the Rockwool so keen to use it. 

Floorboards are 100 year old lovely items that have been  hacked away in quite a few places (not by me until today) but are tongue and groove and absolute 🤬's to get off.

I was anticipating having to cut them up and then put down a new floor (was thinking 24mm ply, same thickness approx, but happy to take suggestions).

 

Just so you know what you are looking at in the pics: there are two external walls and one internal return wall which divides this room from the kitchen. The internal wall is the one with the circular saw  next to it. 

 

Now I can see the subfloor I have a few observations:

1. Damp. The side return wall (the one with the socket and circular saw plugged in) was definitely damp and lime plaster blown. Hacked off the blown bits and I'm sure bricks will dry out now -the bit above this looks dry. My best guess is that this wall is not sitting on a DPC (the external wall is, this is an internal wall and has upstairs floor joists sitting on it so imagined it would be a 9" thick wall, I'm a little preturbed to see the bricks are stacked as though it might be a single skin). The external wall was nothing like as damp.   Is a reasonable hypothesis that lacking a DPC it's just sucked up moisture from the ground which then hasn't been able to escape (lots of paint and paper both sides??)??    - There is a drain the other side of the wall, so that may not be helping, but again I would have imagined the external wall would have been worse (it seems reasonably OK).  I know the drains themselves are in good condition.

 

2. Ventilation - how to get more. I've got one ventilation grate on this side of the room (there's one more diagnoally opposite - and that's it for this room). Though I notice the top of the grate is level with the top of the floorboards. No wonder it was blowing a gale into the room.  Any suggestions for how I might easily (?) get more ventilation to the subfloor - it looks like on the long external wall the bit under the DPC is a concrete block. I could get a French drain outside this wall to allow me to get some ventilation lower down e.g. through the concrete block - though I'm a little worried about whether that will even be possible (I can access a core drill readily) or stupid (avoiding house falling down being the primary concern).   Do you normally put ventilation holes above or below DPC or does it not matter?

 

3. Ventilation grate - how on earth to deal with this with insulation? Given its location am I good to just bring down wood fibre insulation from the wall in front of the grate?

 

4. Joists. These are 3x2 joists and so a bit more puny than I was imagining. They're also loosly sitting on top of the mini 'walls' in the middle of the room. Is it worth replacing them or upgrading to something  more substantial - if so what??

 

5. Gas pipe? - There are two pipes in the pics, one is cut off which is a supply to a disused fireplace. One is in the corner of the room, a 15mm pipe, and goes to where (roughly) our gas meter is. Is there any possibility this is supplying the gas meter? 

 

6.  Is my plan for solving this on the right lines? Would you do it differently (and why?). Any tips for getting the floorboards up? And what am I missing/not seeing?  (and am I completely bonkers? I'm hoping to get this done over summer but basically have one day most weekends to do this and evenings - the Ukranian lady who was using the room for a time is now home but I'm worried she might want to come back for winter!!)

 

 

[Nickfromwales]

Hi.

In 30+ years of heating and hot water I have never seen a supply pipe in 15mm copper. I suggest you investigate this properly by lifting floorboards and identifying what gas pipework is in use, and what is redundant. The redundant stuff needs to be cut out and capped off by a GSR'd installer.

Can you upload a pic of the meter, showing the connections and where they go into the floor / wall / other, please?

[larry]

9 hours ago, Nickfromwales said:

Hi.

In 30+ years of heating and hot water I have never seen a supply pipe in 15mm copper. I suggest you investigate this properly by lifting floorboards and identifying what gas pipework is in use, and what is redundant. The redundant stuff needs to be cut out and capped off by a GSR'd installer.

Can you upload a pic of the meter, showing the connections and where they go into the floor / wall / other, please?

Thanks so much Nick. I think that's what I needed to know. Looking at meter you're right it probably isn't the same pipe - the connection at supply looks at least 22mm. No branches off the output pipe from meter either (the one that was there was capped by the GSR person who last serviced our boiler). 

I don't know *what* it is yet but I'll do some digging today to try and identify and won't touch it until I'm sure it isn't a bodge supply line that goes up to 22mm. 

[IGP]

On the ventilation side under the sub floor, could you block the existing ventilation grate as it seems to be above the joists (perhaps that's the camera angle?) and install a number of telescopic vents across the external walls?

 

https://www.screwfix.com/p/telescopic-underfloor-vent-black-220mm-x-215mm/12025?tc=GB2&ds_rl=1249404&gclid=CjwKCAjw1MajBhAcEiwAagW9MTRe19xMEgqXejvA3sjAJjfDdA4wfrH0MDBMF0D0CHKGi1uAmux9nxoCuXcQAvD_BwE&gclsrc=aw.ds

[IGP]

I'm also about to go for the Ecological Building Systems approach to doing my suspended timber floors, https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors and have just bought all the materials from Latzel in Germany (very efficient and prompt!).

 

[Nickfromwales]

2 hours ago, larry said:

I think that's what I needed to know.

No worries. The pic shows a standard incoming gas supply plus EGC (Emergency Gas Control aka shut-off valve) so all good there.

I would seriously consider upgrading all the gas supply pipework under the boards now, in anticipation of changing to a modern boiler downstream. That would very likely require 28mm or 22mm pipework to supply it, and that can do done now relatively economically. If you do change boilers then it will need doing anyways so you either pay less now for hidden larger pipes, or pay more later and have to either wall mount it externally or pull the floors up retrospectively.

 

What boiler do you currently have? If fed via 15mm pipework I assume an older 'heat only' boiler + cylinder?

[larry]

2 hours ago, IGP said:

On the ventilation side under the sub floor, could you block the existing ventilation grate as it seems to be above the joists (perhaps that's the camera angle?) and install a number of telescopic vents across the external walls?

 

https://www.screwfix.com/p/telescopic-underfloor-vent-black-220mm-x-215mm/12025?tc=GB2&ds_rl=1249404&gclid=CjwKCAjw1MajBhAcEiwAagW9MTRe19xMEgqXejvA3sjAJjfDdA4wfrH0MDBMF0D0CHKGi1uAmux9nxoCuXcQAvD_BwE&gclsrc=aw.ds

Ah, awesome idea. Need to read up how you'd install them. Presumably the telescope bit goes alongside the inside of the wall (or you remove bricks to keep it level with the wall?) and not though the cavity itself (this bit of wall does have a cavity, its a dwarf cavity wall approx 800mm high with a 50mm cavity) 

[larry]

2 hours ago, IGP said:

I'm also about to go for the Ecological Building Systems approach to doing my suspended timber floors, https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors and have just bought all the materials from Latzel in Germany (very efficient and prompt!).

 

Nice! Thanks for pointing me to that. I'd seen the website already which had convinced me to avoid using celotex for starters.... 

What size joists do you have?? 

[IGP]

2 hours ago, larry said:

Nice! Thanks for pointing me to that. I'd seen the website already which had convinced me to avoid using celotex for starters.... 

What size joists do you have?? 

No idea yet, all will be revealed in the coming days! 😊

[IGP]

3 hours ago, larry said:

Ah, awesome idea. Need to read up how you'd install them. Presumably the telescope bit goes alongside the inside of the wall (or you remove bricks to keep it level with the wall?) and not though the cavity itself (this bit of wall does have a cavity, its a dwarf cavity wall approx 800mm high with a 50mm cavity) 

I presume like this?

 

[Nickfromwales]

Yup.

[larry]

@IGP thank you - that's perfect. Let me know how you get on with yours!

 

@Nickfromwales thanks... Mystery now solved. It wasn't really a mystery, a bit of digging and I found a cut off 15mm pipe underneath the gas meter.  The pipe to boiler (now only gas appliance) is now in 22mm so all good there. 

 

[IGP]

@larry turns out my floor joists aren’t an even spacing, anything from 12” to 16” centres. 
 

Probably to do with how the joists fit in the spaces created by the chimney breast in the room. 

[larry]

On 01/06/2023 at 11:45, IGP said:

@larry turns out my floor joists aren’t an even spacing, anything from 12” to 16” centres. 
 

Probably to do with how the joists fit in the spaces created by the chimney breast in the room. 

I look forward to hearing what you find underneath! Ours are the same, ie. Uneven spacing but to be honest having now lifted a few boards the bigger issue is that joists are really not in great condition. Ones near the wall in particular are pretty damp and some joists clearly have had wood worm also. Incredibly they aren't fixed to the wall at all, only resting on the piers (which are crumbling) but about 40 nails per joist keeping everything in place. Tried lifting out boards, no dice so just cutting everything up with a circular saw. 

I have added one of the telescopic vents and still plan to add another. 

Then rip everything out, replace joists with treated CLS and fit 22mm ply on top (after insulating of course). Will use a similar approach to you but will use rockwool as I already have it. May put Flexi wood fibre closest to the wall, though to try to help keep on top of moisture. 

 

[IGP]

Yeah so it’s been ‘fun’, not easy in a relatively cramped space and definitely not perfect. Builder was initially unimpressed working membranes but when I did the detail work (taping and AT foaming) was ok. 
 

Hopefully will be easier in the larger rooms! 
 

 

[larry]

1 hour ago, IGP said:

Yeah so it’s been ‘fun’, not easy in a relatively cramped space and definitely not perfect. Builder was initially unimpressed working membranes but when I did the detail work (taping and AT foaming) was ok. 
 

Hopefully will be easier in the larger rooms! 
 

 

Looks good! And well done, you must be pleased. 

Are you also insulating the walls? And did you bring up the floor VCL above or below the DPM? (All helpful for when I do this!)

[IGP]

The walls are already cavity insulated with EPS beads. 
 

I’m fairly sure our joists are just above the DPC so the VCL was automatically above it. 
 

Yeah I’m really happy I managed to spend a few hours to get the details as good as can be expected in a retrofit in such a space.