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DIY Bedroom Internal BISF Insulation Project by Member ED

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Internal Insulation Project of BISF Bedroom by Ed
BISF House has a number of valuable members who take the time to share project ideas, thoughts and designs for the benefit of other members and readers of the site.

In this latest update we follow one such member as he undertakes a project to insulate the rear bedroom walls of his newly acquired BISF House .

Ed knew that his new home required a lot of internal renovation and from the very start he has been determined to keep the buildings original features. He knew that an external insulation system would strip the property of its unique character so internal insulation would be his only option.

Ed obtained as much advice as possible and drew up detailed plans outlining his chosen construction method. He also opened an inspection hole into the existing hardboard wall to expose the timber stud-work and calculate the thickness of insulation required The wall cavity was already well ventilated so solid insulation panels were chosen as they provided excellent insulation properties and continued air circulation.

Ed has recorded his ongoing project in the Your Home section of the website but we feel that his work and dedication requires its own dedicated page so that other members can follow the project. The original posts made by Ed will stay on the Your Home post.

We Shall pick up at the point where Ed starts to check the structure of the bedroom walls.

All of the text below has been written by Ed himself and re-posted here with only minor edits to aid continuity.

I've cut out and removed a piece of hardboard from the back bedroom exterior wall in the corner next to the party-wall to investigate the construction and shed more light on how I'm going to insulate it. I took it out from just above skirting board height and about 50cm high by 100cm long.

It's not quite what I was expecting but it gives me a much better idea of what I'm going to do. I took some photos but they don't really show it very well so I've drawn a cross-section sketch. The timbers are smaller than I imagined, but closer together. Each one is roughly 45x25mm and they are about 50cm apart horizontally and 30cm apart vertically arranged to form a grid. At the steel uprights there are two against the steel vertically. At the base there is a floor plate. The cavity between the hardboard and the inner surface of the steel cladding is 175mm (ie where it is nearest in the corrugation).

My plan is to place Celotex/Kingspan PIR board in the cavity, up to 75mm of PIR would still leave a 55mm cavity for ventilation but the exact thickness will depend on availability/cost. Then 50mm of expanded polystyrene board in the gaps between the studs, then 12mm plasterboard.

I used this u-value calculator:  ..and with the materials described I should get a value of 0.18 W/m2K.

In reality it will not be quite as good as there will be a little cold bridging, but for comparison a new build house has to be no worse than 0.27. I think (the lower the value the better) and inputting the values for the original upper storey BISF construction gives 0.55 assuming the glass fibre insulation is 50mm thick (it's hard to tell how thick is is, as it seems to have collapsed a bit).

Here's my plan (steel and timber original“ rest to be added):-

I may not bother with the polystyrene, as it was a bit of an afterthought., just to fill the gaps between the studwork/noggins.

I'm thinking if the plasterboard is laid horizontally as was specified in the plans, the timber will probably be in the right place for fixing.

I've also made a diagram of the original construction, but I haven't included the glass fibre insulation.

Ed March 12, 2012 at 11:41 am

Yesterday we started rebuilding the back bedroom, and as promised I took plenty of photos. My aim is to refurbish completely to modern standards with extra electrical sockets, ethernet and wall insulation to make the walls at least as good as a newly built house without destroying the BISF character that attracted me to the house to start with.

Here's the room before, decorated in badly hung floral wallpaper that has been stuck over the picture rails etc

On the plus side there is a nice original "shaker" style door and another on the built-in cupboard and a number of other original details

The first job was to roll up the carpet and carefully prize off the skirting boards, picture rails and other woodwork for re-use later. They came off very easily.

The picture rails removed showing edges of hardboard wall covering.

Then the hardboard could be stripped off the walls. It could mostly be removed with bare hands (or gloved to protect from the glass fibre behind).

The original insulation is glass fibre in a brown paper casing. It was actually in much better condition than I expected. It is nailed to the back of the timber studwork with a washer so the nail head doesn't go straight through. The damage in the far corner was where I first opened the wall up to investigate the structure


As you can see the timber studwork/noggins are pretty small and flimsy. They do not match what is in the architects plans, so I guess this part was modified when hardboard was used instead of plasterboard. Interestingly, from the way they are nailed together from the outside, you can tell that each section was prefabricated off-site a bit like a garden trellis, and the whole panel installed in one piece.

The original insulation is glass fibre in a brown paper casing. It was actually in much better condition than I expected. It is nailed to the back of the timber studwork with a washer so the nail head doesn't go straight through. The damage in the far corner was where I first opened the wall up to investigate the structure.

The party-wall is a bit different as the board was nailed to battens applied directly to the concrete blocks.

Next came the messy and itchy job of pulling out all the glass fibre insulation. Underneath the steel is in very good condition it seems.

More to come later as I'm still rebuilding the studwork and putting in insulation, so you can see that too.


Posted : 12 March 2012 11:06 PM
Posts: 29

Hi Ed and Marc
really great to see how you both have gone about your projects as i will be doing the same at some point bathroom first its been really useful. Interesting what you were saying about the joists and noggins as i have my lounge celling down

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Posted : 13 April 2012 6:21 PM
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Hi Ed
Great to see the room partly plastered, I bet you can really feel the difference in warmth already!

I remember from a previous job that the noggins were all loose, as in free moving and slotted into the support beams which can be a bit of a pain when trying to line up the screws from below. I agree that overboarding just doesn't seem the best way so I think I will relace the noggins on this job to match the metric plasterboard sizes.
I was fortunate last time as I did most of the stripping down of the ceiling and left my friend to do most of the boarding. I remember his frustration with the shifting noggins lol and how comical it was with him downstairs with the screws and myself in the loft trying to guide the noggins in place.

I think using right angle timbers is a great idea to keep the noggins stable. If I remember correctly the noggins wern't very wide either.

Looking good though my friend, You have done a huge amount of work in such a limited time but it's well worth the effort. Smile

Posted : 14 April 2012 2:11 PM
Posts: 0

Thanks Marc, as you can see i've used 900x1800mm boards for ease of putting up and placed them at right angles to the original noggins. It did involve putting up several rows of extra noggins between the original ones to hold them in place. The noggins are only narrow, 37x75mm I think, but some of them (where the old boards met) are doubled up so I placed the new joints there too.

I used one of those electronic stud detectors to find the noggins when screwing the boards up, because they are not completely evenly spaced.

Thinking about it again, it might have been easier to hold the noggins in place by screwing long pieces of timber in on top of them in the loft and then only putting the individual cross pieces in where the boards meet.

I don't think you'd want to get rid of the original noggins because then you'd have to notch new ones so you wouldn't really gain anything and it would probably be difficult to notch them all the same to get the ceiling level (I imagine they were all delivered pre-notched from the factory). I can't think of any way of attaching them to the steels apart from slotting them in like the originals.

I did it all in a bit of a rush so unfortunately I didn't take photos, but I'll take some from above.

Posted : 15 April 2012 6:44 PM
Posts: 0

Hi Doug, the ceiling noggins are just like that except they are thinner and of course once you take the ceiling boards off they're loose, instead of being held in place by floorboards.

With hindsight, it may have been better to fix them in place from above before removing the ceiling boards.

Posted : 10 May 2012 2:46 PM
Posts: 0

Hi all, just a quick update with some photos. As you can see it's almost done, just needs some touching up and the doors putting back, radiator and lamp replacing etc but I need a bit of a break from decorating now!

Is it OK if at the end I rewrite things a bit because there are some things I did differently from how I planned and some things I discovered along the way?

This post was modified 6 months ago by Admin
Posted : 10 May 2012 2:52 PM
Posts: 0

I have taken the old radiator out as it was the old single type with no thermostatic valve. It's on a microbore system and had a strange connector with the inlet and outlet at the same place. While at it we replaced the radiator in the main bedroom which was directly behind it, taking the opportunity to put some extra noggins in for it to be attached to while the hardboard was off the wall (the old radiator was just attached to the hardboard and was falling away from the wall).

We are going to replumb them so that the pipework runs underneath the floorboards, as it does to the bathroom radiator, instead of coming out of the built-in cupboard in the back bedroom and out of the flue box in the main bedroom.

While repairing a floorboard that had been cut to put in the central heating but left unsupported (I wondered what the hole under the old carpet was!) it was possible to see how the 8mm microbore central heating pipes and ring main cables just fit through the gap between the ceiling and the steel floor beams.

But the mystery to me is how the 15mm hot water pipe gets from the hot water cylinder to the bathroom washbasin. Do the steel beams have special holes for the pipe?

Posted : 15 May 2012 10:08 PM
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*Hi Ed, the beams don't normally have any holes cut in them but I am all too familiar with microbore as it was fitted into one of my properties just as you described. Lying just onder the floorboards Smile

If I recall correctly, I think the 15mm hot water pipe leaves the cylinder in the bedroom cupboard up through the loft space and returns into the bathroom inside the stench pipe casing. Don't take my word on that though as it has been a while since I refitted one of the bathrooms.

Does your feed come to the sink via the stench pipe casing?

Also, I've spent the last few days trying to develop a way for you to access and edit your entire bedroom post. It's been a bit of a nightmare lol but I'm still working on it. I've been sat here all day so far thanks to the rain and thunder here but I haven't got very far as I have also been trying to develop a better comment system of forum integration.

I really liked your last update right down to the picture rail detail.

Amazing job!

BTW is your central heating fed from a boiler or the immersion tank?


Posted : 16 May 2012 12:48 AM
Posts: 0

Hi Marc, I'm glad you like it! I think the two-tone colour scheme works well. Putting the woodwork back up after reboarding the walls was quite an effort but it was worth it as I think it gives a nice combination of original BISF style with a contemporary update.

Our hot water comes from a cylinder in the cupboard in the main bedroom next to the boxed-in flue, and it is heated from a back boiler behind the fireplace downstairs. It comes up from under the floor under the handbasin and definitely doesn't go through the loft. Now I think it goes through the wall between the hall and kitchen downstairs (under the steel beams) and that is why there is only an odd-looking half-height glazing above the kitchen door unlike all the others which have glazing all the way to the ceiling. Perhaps the hotwater pipe goes above the glass. Originally I assumed that was a later bodge, but I notice the half-height glazing is in the architects plans so there must be a reason for it.

Posted : 20 May 2012 10:14 PM
Posts: 29

*Hi All ref the hot water pipe, a 22mm pipe leaves the cylinder  and drops into the floor of the back bedroom and runs towards the window then bends about .5 metre from the outside wall passing through a hole in the I Beam and continues to the bathroom both hot and cold supplies then drop down the side of the soil and vent pipe to the kitchen hope this helps


Posted : 21 May 2012 2:52 PM
Posts: 0

Hi Doug and thanks for your message. I have a radiator on the wall between the two bedrooms and had some of the floorboards up in front of it to repair/replace them where they had been damaged when the central heating was put in (in the 1970s at a guess). I never noticed a 22mm pipe under there though but perhaps it was too far to the left to notice.

I'm still wondering what is above the kitchen door. Everything about a BISF house is logical but sometimes a bit surprising, so I think there must be something in there. There are pipes sticking out of the wall next to it which are quite an eyesore and can hopefully be removed. They are not hot water pipes in use because they do not warm up if you run hot water


Kitchen/hall doorway (half-height glazing)


Kitchen/hall doorway with pipes


Kitchen/dining room doorway (full height glazing)


Some more decoration

This post was modified 6 months ago 6 times by Admin
Posted : 21 May 2012 5:50 PM
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