Spare Room Preparation and Day 1 insulatingmyhouse

Spare Room  Preparation and Day 1 insulatingmyhouse

Spare Room Preparation and Day 1

As wed never fitted solid wall insulation before we decided to try it out in the simplest room first so as not to run before we could walk. In our case this was the spare room. There are a few advantages to this:

Firstly, as the name implies, it is spare, so we could more easily put up with the disruption than with other rooms (although we still needed somewhere to put furniture and insulating materials).

Secondly it has no coving (such as what we have in the living room) which would have complicated the process.

Thirdly the walls are vertical (well almost) and uncomplicated, unlike the main bedroom which is in the roof and has beams and a dormer window to contend with.

The first photo here shows the room before we started work (sorry to air the laundry in public). First job was to move all the furniture out of the room, this took a few hours but ground to a halt when we discovered moth damage to the carpet. Closer inspection found live moths in various stages of their life-cycle. After reading up on possible treatments we put everything we could through the washing machine on a hot wash and bought mothballs, moth paper and a special powder for treating the carpet. Its too early to know if this has worked, but at least we were expecting to move all the furniture anyway, so it wasnt as much extra work as it might have been.

Once we did clear the room (the moth treatment took a few days to sort out) I removed the window architrave and cill with a borrowed crowbar. Care was required to avoid breaking the window and the frame. I also exposed the air-brick that has been covered up by the previous owners. The plaster around the timber lintel was very loose and fell off in large chunks, so we chipped away until wed only left plaster that was firmly attached theres no point gluing insulation to plaster thats about to fall off. The same applied to the lining paper I picked at it by hand until there was no loose paper left.

Having removed the window architrave I began to notice a number of gaps in the silicone sealant between the uPVC window frame and the brickwork. As the sun angle changed throughout the day the light revealed new gaps, some of them were large enough to get a finger or screwdriver through. These holes had been linking the cavity behind the architrave with the outside the world. This meant that the only barrier between inside and outside had been a thin plank of wood with gaps around it! Professionally fitted windows just a few months old, ah well its worth checking!

So, we got some brown silicone frame sealant and filled all these gaps going back at different times of day to check for sunlight getting through. Now Im alert to it Ive noticed gaps in the sealant around some of the other windows, so Ill be sealing these up too.

The next surprise was that, upon inspecting the brickwork we revealed around the window, we found that there is cavity of sorts in solid brick walls. Apparently this is normal; most bricks in solid brick walls run along the line of the wall (known as stretchers), but there are a few that are placed at right angle to this and so span the thickness of the wall (these are called headers). The length of the bricks is slightly more than twice their width, so, in order to avoid having the headers sticking out through the wall, a small cavity is created between the stretchers. This cavity is discontinuous because the headers span it at regular intervals, there are also often bits of mortar that block the cavity in various places. I found that I could get my fingers into the cavity fairly easily. Apparently there is much debate about whether this cavity allows air to pass through it and on whether this process could by-pass the benefits of external wall insulation. The rational behind this argument is that if external air can get into this cavity (perhaps around the eaves or air brick or windows etc.)  then it would be inside any external wall insulation and dramatically reduce its benefits. In our case there certainly is a significant air path through this cavity, I know this because I found a number of polystyrene beads caught in cobwebs around the window. Where had these come from? Well, in another post I have talked about how I have been using polystyrene beads to insulate the wall of the bathroom, these must be the same beads. In order to get to the window of the spare room these beads must have got around the edge of the bathroom window, into the cavity and then made their way around 3 metres back along the cavity to the spare room window.

Anyway, I sprayed expanding foam into the cavity as far as I could access it. I found that it took a long time to cure because of the restricted amount of air movement around it, it was still expanding around 12 hours later.

This was the end of the preparation stage that we did before our work party arrived to help out. We had arranged for Andy Walker to come around for a day, this is a service he offers on a day rate including advice, tools as well as getting stuck in with the work. As well as Andy we had invited my parents to come and help out for a few days. My wife and I had taken 3 days off work too, so in total we had a clear run at it for 5 days.

The first job of the day was to cut a slot in the floor along the outside wall. We are fortunate that the joists run parallel to the outside wall, this is good because it reduces the risk of cold bridging that occurs when a joist runs from the warm space into the cold outside wall.

The joist closest to the wall will generally be just a few inches from it, we want a continuous layer of insulation and a continuous vapour control barrier to run along the whole of the outside wall, so we want to have insulation and a vapour barrier running through this gap between the joist and the outside wall. Being careful not to damage the joist, Andy used a circular saw to cut off the ends of the floor boards nearest the outside wall.

As usual in a house of this age, no lines are straight and there are no right angles; so we found that the joist is not quite parallel to the outside wall. This is not a problem, it just means cutting the insulation boards to a slightly different shape for one end of the wall to the other.

Whilst this was happening we also cut off the end of the skirting board that joined the outside wall. The tool we wanted to use for this is a multi-cutter, but it wasnt working, so we used a hand saw.

Once all the floorboards were cut we found that polystyrene beads had found a way into the floor void too. It appears that the floor void connects to the adjacent bathroom; I had expected the partition wall to continue down to the floor below.

I want the beads to stay in place so rather than continuously leak out of the bathroom wall, so I plugged the gap with some expanding foam. I also put expanding foam into a few other gaps wed found in the brickwork.

As well as insulating the external wall we had also decided to insulate the first section of the adjoining party wall and the whole of the chimney breast. As part of this process, the next stage was to create a slot in the floor along the party wall. Unlike the slot along the external wall, the floorboards run parallel to this slot, so all we had to do was remove the floorboard closest to the wall with a crowbar. This revealed another surprise. We found a large void, at least one cubic metre, under the floor where the party wall meets the chimney breast. The chimney breast on the floor below is wider, and I had always assumed it was solid. However it turns out that the solid part of it tapers towards the top, but it has been made to appear not to by a timber partition that continues straight up to the ceiling. Having removed a floorboard in the bedroom we could see down into the void behind this timber.

This gave us the opportunity to easily insulate a section of the chimney breast and the party wall in the living room, so we filled the void with mineral wool.

We also stuffed mineral wool into the gaps between the joists running away from the party wall, we filled these gaps for a distance of around 500mm away from the wall. The aim here is to insulate this section of party wall whilst not creating a condensation risk around the joists. Unlike polyurethane boards, mineral wool is permeable to air, water and water vapour, so insulating in this way should still allow the joists to breathe.

Another thing we found under the floor was a small piece of wood wedged between the first joist and the outside wall. Apparently this was common practice when our house was built; if a joist was bowing when it was fitted the solution was to put in a bit of wood like this to hold it in place prior to nailing down the floorboards. 100 years later the timber has settled down and the wood was loose enough to pull out by hand; we did this as it was no longer serving any purpose.

As well as running the insulation layer down to meet the floor below, we also wanted to run it upwards to meet the insulation that will eventually be installed in the room above. So, we started cutting a slot in the ceiling to allow this. The ceiling turned out to be full of black soot and grit, making this a very messy process. We also found that these joists run into the outside wall (unlike those on the floor below), we changed our plan to insulate between these joists with mineral wool (as wed done with the party wall as mentioned above). Well do most of this insulating when tackling the room above, but for now we stuffed the hole wed made with mineral wool and left it.

Right! Now to actually insulate something! First job here was to insulate the sides of the window reveal. The space available here could varies a lot from one window to another, but the gap wed found between the brick and the uPVC frame was around 50 to 60mm. This gap is bridged by a series of strong screws that go through the window frame into the brickwork. Once the timber architrave is removed this does present a rather unnerving image as the frame is suspended in the centre of the hole like the hub of a bicycle wheel its stronger than it looks.

To fit the insulation we cut a piece of 50mm insulation board to the right length and width and then pushed it into the slot until it hit the screws we then took it out again and cut slots where the screws had left a mark on the insulation. We then pushed it back in to test the fit. Finally we took it out again and applied expanding foam adhesive before pushing the insulation back into its final position for the last time. We held it in place with some tape as the expanding foam has a tendency to push the insulation away from the wall. Once this had dried we cut any excess foam off to be flush with the wall using a hand saw.

At this point we also filled in the air brick wed uncovered. Before doing this we had a discussion about ventilation. Every room should have some sort of ventilation, so we didnt want to cover up the air brick without having an alternative mean of ventilation. The air brick had been covered up for several years already, so we felt that we were unlikely to cause a new problem by recovering it. However we were also making the room more air-tight than it had been before remember the holes around the window that wed sealed. So we discussed the alternative ways of ventilating the room. We could:

  • install a fan in place of the air brick we decided this would be unnecessarily complicated and potentially cause problems with noise as well as using energy to run.
  • We could drill through the uPVC window frame to create some trickle vents and fit trickle-vent covers to improve their appearance.
  • We could simple leave the window very slightly open when we feel ventilation is required. The window has facility to be locked in this position so there should not be a security issue.

In the end we decided to opt for leaving the windows open a crack and see how we get on. We will monitor the situation and see if we have any problems associated with poor ventilation, (such as damp, mould and poor air quality). If we do then we may try out one of the other options.

So having decided that we filled in the void behind the air brick with 2 layers of insulation and filled around these with expanding foam adhesive.

Next stage was to tackle the main part of the outside wall. Firstly we cut a sheet of Visqueen (a thick construction-grade polythene)  to the width of the wall (plus a little) by around 1 metre wide. We then rolled this up into a long tube which we placed into the slot wed cut in the floor, as we did this we left one long edge hanging out of the slot, we then temporarily taped this edge to the floor.

Why were we doing all this? Its to form part of the continuous vapour control barrier. When installing insulation it its important not do anything that could cause damp to build up as this could cause mould growth or decay in the structure of the building. One of the ways this could happen is if warm humid air in the house can get into the layers of insulation and work through to the cooler surfaces near to the outside wall (or on the wall itself). I hardly need point out that air can get through really small gaps, so cracks between insulation boards or the areas where these boards touch the walls or ceiling or floor all provide an opportunity for this to happen. The insulation boards come with a foil coating to help prevent this, but that alone is not enough. We took great care to ensure that all gaps between insulation boards are sealed with foam glue and then covered with foil tape. But we still need to deal with where the boards meet other walls and the ceiling and floor. Read on to see how we approached these challenges

The insulation boards we ordered are 1220mm x 2440mm (thats roughly 4 by 8) Our stairs are narrow and have a 180° bend at the top, so there was no way we would get these up the stairs. Therefore we cut them lengthways outside before bringing them into the house its really worth thinking these things through beforehand.

We now took the first of our large 100mm insulation boards and held it against the wall to test the fit. This is also an opportunity to see how non-linear and non-vertical the wall is (using a large spirit level). This down we took it down again and applied some expanding foam adhesive to the back of it; we applied a little more where wed noticed the wall bending away from the vertical. In most cases we applied a single bead of foam roughly around the edge of the boards and then a zig-zag across the middle. Remember to leave the foam to cure for around 5 minutes before trying to stick the board to anything.

Spare Room  Preparation and Day 1 insulatingmyhouse

We placed the board against the wall and pushed it down into the slot at the edge of the floorboards on top of the Visqueen roll. It needs to be held in place for a few minutes or it will tend to move a little as the foam adhesive cures.

Where these boards meet an adjoining wall we put foil tape along the corner to extend the vapour barrier. We then sealed this to the wall by applying a bead of silicone sealant along the wall before putting the insulation in place. Any remaining gap between the insulation and board and the wall was also filled with silicone sealant.

There now follows a series of photos showing how we continued this process along the wall.

Where the insulation boards butted up to each other we also applied a bead of foam adhesive along the edge of the insulation to stick them together.

In some places we needed to cut a small section out of the bottom of the insulation boards to fit them into the slot in the floor. This wasnt always required because the joist didnt run perfectly parallel to the wall, so the slot tapered towards one end slightly.

Once the boards were securely glued we went along all the joints filling in any gaps with more foam adhesive. We could have used normal expanding foam for this, but the foam glue cures more quickly and expands much less, both of which are helpful for this job.

Once all the bottom row of boards was in place we stuck the upper edge of the Visqueen sheet to the front face of the insulation boards using foil tape. This is an essential element of the vapour barrier as it continues the barrier down below the floor level. When we come to insulate the rooms below we can cut a slot in the ceiling and pull the rolled-up Visqueen down and attach it to the foil face of the new insulation in the same way. Using this method there should be no way that moisture can get through the insulation between the rooms above and below.

In several places we found the ceiling and walls were not straight, although we tried to cut the insulation to match the irregular shapes we didnt always succeed and so ended up filling in some gaps with thin strips of insulation board. This is Ok so long as these bits are well glued in with the expanding foam adhesive and then all joints covered in foil tape.

Once all the insulation boards were in place we went around securing the larger insulation boards with a type of 200mm Rawle plug. This is an extra way to ensure that the insulation stays in place. The Rawle plugs have 2 parts, a plastic tube with a plastic disk on one end and a plastic pin that fits inside the tube. We drilled 10mm holes through the insulation and into the brick behind using a 300mm masonry drill-bit. We then pushed the tube-part into the hole and tapped it firmly in with a hammer. We then tapped the plastic pin into the tube (see photo). The pin forces the tip of the tube to expand and grip the brickwork and the plastic disk at the other end stops the insulation pulling away from the wall. Apparently Andy has tested one of these into a ceiling joist and found it could hold his weight. in a few cases we couldnt get the pin all the way into the wall, so we cut them off with side-cutter pliers.

The only place Ive been able to find these Rawle plugs available on the internet is the companys own website, and they only sell them in boxes of 250 which is a bit excessive when I only wanted 25 for the whole room. Andy was happy to overcome this by selling us some that he had.

We used 4 of these plugs for each of the 8 by 4 boards, but didnt use any on anything smaller than about half this size. In a few places we  put in an extra plug in order to help flatted insulation boards that were slightly warped. Different length Rawl plugs are needed depending on the thickness of insulation board and the condition of the wall. For the 50mm insulation boards we used 90mm Rawl plugs.

This done we covered the heads of all the plugs with foil tape and went around cutting off excess foam and covering any other joints or cracks in the foil with more foil tape:

Although we hadnt finished applying insulation to all the walls, we wanted to get a couple of plasterboards in place before Andy left so he could show us what to do. We spent some time discussing where we wanted the joints in the plasterboard layer to be. This is important because we were planning to do the joint filling ourselves and so we were expecting the joints to not be perfectly finished (as a professional plasterer would achieve). We wanted to keep the joints away from peoples eye-lines so as to make them less obvious. We also worked out that we could hide a couple of them behind the curtains.

I had bought 6 by 3 (1800mm by 900mm) plasterboards with tapered edges. Larger boards are available and I would have got these so as to reduce the number of joints, however Id figured out that I couldnt get larger boards up the stairs, so Id opted for this smaller size.

The tapering of the edges makes it easier to achieve a smooth joint finish, although this is still a tricky process. Only the long edges of the boards are tapered, so the most obvious joints would be where the short edges meet.

Having figured all this out we cut a plaster board to size and tested it against the wall to check the fit. To cut the plasterboard we could use a normal Stanley knife, we scored along the line of the cut and then pushed down on one side of the board until it snapped along the scored line. We then used the knife to cut along the paper on the other side of the board. A quicker way was to use a tool of Andys called a Blade Runner that comes in two halves; each half has a blade that can score the board on both sides at once. This is achieved by a very strong magnet that keeps the bottom half directly below the top as you push it along. Very clever.

To stick the boards in place we used solvent free Pinkgrip (see discussion on this in the post on the basement door ). We used a dollop the size of a walnut whip spaced about every 6 inches in a grid pattern.

Pinkgrip grips well, so after pushing the plasterboard to the wall and checking it was straight we could let go and it would stay in place unless pushed. The exception to this is that if it was not supported from below, it would creep down the wall, but in most cases we applied the lower boards first, so this wasnt a problem.

The last job of the day was to fit a board for attaching the curtain pole to. For this we used a slightly different type of board which is like a plasterboard but with wood fibres mixed in, this makes it much stronger and so better able to support the weight of the pole.

To attach this board we used Pinkgrip in the same way as we used for the normal plasterboards, but to be extra secure we also used some of the long Rawle plugs with the disc on the end trimmed down, see photo.

Its always helpful to have a few people around to hold things in place whilst you mark where to cut and drill!

So that was the end of day 1. Wed made a lot of progress thanks to the preparation and having 4 people working in the room and another preparing meals and refreshments, thanks to all.

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