Floorboard rennovation questions

[Dylan123]

Hi, a few questions if anyone can help:

I have a 1939 terrace. It has a large crawl space below.

The floorboards look good so am insulating them underneath and will finish the top without taking too many up in the process.

I intend to insulate the whole ground floor.

1. what material is best? I looked at earthwool and rock wool but it looks really expensive. Like £800 for the whole ground floor. I found some kingspan thermoset rigid and it is much much cheaper. Can you advise the most acceptable material at the cheapest cost?
Also how thick? I know it’s a complex calc and depends on my wall thickness etc but just explain like I am 5 and tell me what to buy and look for!

second/third question:

see pics:

- I have a kind of stained but around the outside of the rooms. See the darker wood (it then turns into stripes of stain). I am confused what this is, I thought these homes in the 30s would have been carpeted - was this decorative wood stain? Anyway, can this be sanded out? Can it be taken off with solvent? Can I just turn the boards over? Or, can I just put new boards in? How do I get this looking neat when the eventual sand and varnish is done? Or should I just use the paint stain stuff so it all looks the same?

sexind question - do you know what type of wood my boards are? I think the joists are oak. Any ideas?

Some of the boards have some holes and damage so I need to know wood type so I can put a bit of wood filla and stain in there.

help very much appreciated amigos!

 

[Deleted member 174758]

Sorry not an engineer, however the cheapest insulation always seems to be Kingspan/Cellotex with the minimum thickness we put into floors being 75mm

I have a kind of stained but around the outside of the rooms. See the darker wood (it then turns into stripes of stain). I am confused what this is, I thought these homes in the 30s would have been carpeted - was this decorative wood stain?

In the 1930s you'd have possibly had lino in the "working" rooms, like kitchens and toilets, and rugs which didn't reach to the edges of the room in other rooms. The resulting margins around the edges of the rooms were often either stained and lacquered or painted. This stuff can be difficult to sand out. AFAIK fitted carpets really only came in in the 1960s

If you want to take out the staining and sanding hasn't worked you may be better off looking at a 2-part wood bleach which will completely remove colour (to the point where you may feel the need to put a light stain on to get some colour back). As ever with this sort of material take all the recommended precautions and treat an unobtrusive test area before going "hog wild"

Lifting and turning boards can be a tricky process because anything that has been on the floor for 70 or 80 years can have a tendency to split. New boards are an option, but you would need a timber yard who could machine stuff to the exact same sizes as the boards currently on the floor. You are also unlikely to be able to match the tongue and groove pattern on the existing boards (if any)

do you know what type of wood my boards are? I think the joists are oak. Any ideas?

Your floorboards are pine. In the 1930s I'd suspect Canadian in origin. I very much doubt that your joists are oak - it was simply too expensive, even then. More than likely the joists are redwood (pine). Even in imposing Victorian buildings such as banks the beams and joists are generally some type of softwood (or at least all the ones I've worked on have)

 

[Dylan123]

Sorry not an engineer, however the cheapest insulation always seems to be Kingspan/Cellotex with the minimum thickness we put into floors being 75mm


In the 1930s you'd have possibly had lino in the "working" rooms, like kitchens and toilets, and rugs which didn't reach to the edges of the room in other rooms. The resulting margins around the edges of the rooms were often either stained and lacquered or painted. This stuff can be difficult to sand out. AFAIK fitted carpets really only came in in the 1960s

If you want to take out the staining and sanding hasn't worked you msy be better off looking at a 2-part wood bleach which will completely remove colour (to the point where you may feel the need to put a light stain on to get some colour back). As ever with this sort of material take all the recommended precautions and treat an unobtrusive test area before going "hog wild"

Lifting and turning boards can be a tricky process because anything that has been on the floor for 70 or 80 years can have a tendency to split. New boards are an option, but you would need a timber yard who could machine stuff to the exact same sizes as the boards currently on the floor. You are also unlikely to be able to match the tongue and groove pattern on the existing boards (if any)


Your floorboards are pine. In the 1930s I'd suspect Canadian in origin. I very much doubt that your joists are oak - it was simply too expensive, even then. More than likely the joists are redwood (pine). Even in imposing Victorian buildings such as banks the beams and joists are generally some type of softwood

thanks - that’s a great help.

the joists are a darkish red colour.

one other thing, I lifted a board (slight Nick where I took it up but I can glue it in or repair) and the joists are dry and no rot, solid as a rock. There are air bricks both ends of the house. The space is mummified - dry as a desert. I was quite surprised at the condition down there for the age.

when adding insulation, provided there’s air bricks I presume I’m alright reference to damp?

also, the fireplace stack (the thing it sits on and holds up the chimney stack) as a kind of white/grey sheet in it. Between the brick and the concrete hearth.

I was concerned this was asbestos (will wear a P3 as I haven’t looked at the pipes and potential lagging yet before I get in there) but my dad things it’s an old form of DPC. I don’t think the house has a DPC given it’s pre war, but he said that even so, fireplaces used to have them as the heat would wick water up.

I just wonder if you have any comment on this - last questions I promise!

 

[JohnD]

Most of the heat loss through a wooden ground floor is draughts. Obviously there is no convection and very little conduction. Stuffing mineral wool between the joists, especially round the edges of the room where there is a gap under the skirting, will block it.

Wool does not need to be cut to a perfect fit and sealed like rigid foam boards, and is cheaper. It can be pressed into irregular gaps. Loft rolls are easy to handle and widely available.

It is also safer in a fire, though that is rare under a ground floor.

 

[Dylan123]

Most of the heat loss through a wooden ground floor is draughts. Obviously there is no convection and very little conduction. Stuffing mineral wool between the joists, especially round the edges of the room where there is a gap under the skirting, will block it.

Wool does not need to be cut to a perfect fit and sealed like rigid foam boards, and is cheaper. It can be pressed into irregular gaps. Loft rolls are easy to handle and widely available.

It is also safer in a fire, though that is rare under a ground floor.

surely stuffing mineral wool between the joists and the edges is still insulating it and will require buying tons of it and going underneath and putting netting up? Is that what you’re saying?

im trying to avoid lifting the boards. So are you saying go under, put nets and stuff mineral wool as opposed to fitting board? Then seal the gaps from the top?

how deep should it be- depth of the joist? How tight should it be packed

 

[JohnD]

surely stuffing mineral wool between the joists and the edges is still insulating it and will require buying tons of it and going underneath and putting netting up? Is that what you’re saying?

im trying to avoid lifting the boards. So are you saying go under, put nets and stuff mineral wool as opposed to fitting board? Then seal the gaps from the top?

how deep should it be- depth of the joist? How tight should it be packed

Whatever you use, you will be crawling under the floor.

your ground floor is pretty sure to be exactly the same size as your loft.

100mm loft rolls will be fine. 170 or 200mm will bring little extra advantage, but use whatever you can find cheap. your joints will probably be around 7" deep.

you will not have to "seal gaps from the top" with quilt because, unlike rigid boards, it does not leave gaps for draughts.

 

[Dylan123]

Whatever you use, you will be crawling under the floor.

your ground floor is pretty sure to be exactly the same size as your loft.

100mm loft rolls will be fine. 170 or 200mm will bring little extra advantage, but use whatever you can find cheap. your joints will probably be around 7" deep.

you will not have to "seal gaps from the top" with quilt because, unlike rigid boards, it does not leave gaps for draughts.

thanks - and I don’t need a membrane? Just mineral wool - that’s it?

 

[Deleted member 174758]

when adding insulation, provided there’s air bricks I presume I’m alright reference to damp?

Just make sure there is still some space for air to circulate

also, the fireplace stack (the thing it sits on and holds up the chimney stack) as a kind of white/grey sheet in it. Between the brick and the concrete hearth.

Could be Asbestolux or Supalux fireboard. Both are white, but Supalux generally has brassy flecks in it which asbestos boards don't. If in doubt get it tested. Both are commonly found in hearths, etc. Asbestos boards were commonly used until the 1990s and were only outlawed in 1999. If you do need to handle asbestos, don't disturb it (cut, saw drill, etc), do damp everything down to keep fibres from becoming airborne, wearable a disposable coverall/gloves/shoe covers to avoid contamination and under no circumstances ever use a domestic vacuum to Hoover up any dust - the filters simply aren't up to the task and all you will do is blow asbestos fibres all over the place.

You sometimes get DPCs in pre war houses, but not as we now know it. Very often they did it by using a layer of slate or bitumen

 

[Deleted member 174758]

surely stuffing mineral wool between the joists and the edges is still insulating it and will require buying tons of it and going underneath and putting netting up?

A simpler way is to buy mineral wool batting and saw it so that it is a tight fit between joists. A few strip gs staples beneath it will then hold it if it ever drops

 

[Dylan123]

Just make sure there is still some space for air to circulate


Could be Asbestolux or Supalux fireboard. Both are white, but Supalux generally has brassy flecks in it which asbestos boards don't. If in doubt get it tested. Both are commonly found in hearths, etc. Asbestos boards were commonly used until the 1990s and were only outlawed in 1999. If you do need to handle asbestos, don't disturb it (cut, saw drill, etc), do damp everything down to keep fibres from becoming airborne, wearable a disposable coverall/gloves/shoe covers to avoid contamination and under no circumstances ever use a domestic vacuum to Hoover up any dust - the filters simply aren't up to the task and all you will do is blow asbestos fibres all over the place.

You sometimes get DPCs in pre war houses, but not as we now know it. Very often they did it by using a layer of slate or bitumen

looks just like pictures of asbestolux.

I will mix pva with glue and spray it.

removal looks like the whole thing needs taking apart. Or I could apply some render over the top?

I know you’re not a safety consultant. I can work around it without touching it.

Any sensible suggestion seeing as I can’t afford £5k to remove it professionally?

 

[Deleted member 174758]

We always get told to encapsulate rather than remove for the same reasons - cost

 

[JohnD]

I have a 1939 terrace.

Asbestolux in 1939? Earlier than I'd have thought.

photos would be useful.

 

[Dylan123]

Asbestolux in 1939? Earlier than I'd have thought.

photos would be useful.

is it safe to pull up the floorboard to look with my child in the house? It won’t disturb it but I am worried it may pull a cloud of dust up or let fibres in.

saying that they can already get up through the cracks in the floorboards.

 

[JohnD]

thanks - and I don’t need a membrane? Just mineral wool - that’s it?

The dense batts are more expensive than the loft rolls, and have more weight (so are a bit better at muffling sound)

you could use a porous material such as landscape membrane, and staple it to the joists to hold the insulation up. Old practice was garden netting.

roofers breathable membrane might also do.

at the ends closest to the airbricks, use something more solid, like an offcut of ply, because it is vital not to flop down and block the flow.

 

[JohnD]

Asbestolux in 1939? Earlier than I'd have thought.

photos would be useful.

On checking, I see a similar board was introduced in the 1930's, and wartime prefabs were built with asbestos-cement boards (which are different)

it just seems an odd choice to me in your case.

Some of the old builders will know.