Garage Conversion & New Porch

How I converted a garage into a habitable room to building regulations and rebuilt the porch. With all garage conversions, building regulations apply like insulation, approved electrics, escape routes, window heights etc.. so a building regs submission should be made.  See the below image so you have an idea what needs to be constructed.


My plans and building regulations did not state any details for the porch, just for the general construction e.g. construction of the floors, brickwork etc. As before the floors would have to be insulated, any non-cavity walls would have to be lined with insulation, ceiling insulated, electrics would have to be installed, UPVC windows with trickle vents and so on.

I recently visited a friend who paid £3700 including labour for approximately 1m x 2m wide new porch which involved no demolition work, just the cost of a small skip. He had a few quotes that were in the excess of £4500. For the work I am about to do, I estimate rebuild will be roughly between £7500-£9000 including labour. I estimate just the materials & UPVC will cost £3000.


Anyway, some time ago the garage was extended out. Although it was very solid, the garage walls did not have any cavity. Also the bricks were slightly browner that did not match the rest of the property nor the bricks used on the new extension. I decided to take it all down and rebuild it as it will be the main feature of the property. I plan to re-build the walls with a 100mm cavity, using new 73mm (imperial) Ibstock Multi Rustic bricks as used before.

I estimate the costs as follows excluding any electrical work for the new porch and full garage conversion:

Description Estimate Actual
Facing bricks £200, Engineering bricks £80, Thermal blocks £100, £380 £
2 Ton sand £70, 2 tons ballast £60, 20 bags of cement £80 £500 £
2 Air vents £8, 2 telescopic risers £6, 2 x adaptors £10, pipe £8 £
Wall starters £30, wall ties £10, metal work £10  £20
Roof Timber £150, timber fascia £40  £200
Tilies, membrane, laths  £175  <£400
UPVC Window for garage  £250  £340
Porch UPVC: Double doors £350, 2x porch windows £250, side window £150  £750  £860
Insulation  £500  <£200
Floor screed and self levelling compound £250  £94

The concrete floor was solid enough, between 150mm-200mm thickness so the internal thermal blocks would be built of this slab. I asked the building regs inspector months ago if I could build the wall off this slab. She said dig down the front and see if it strong enough. I also noted a problem; the concrete slab would have been exposed by 20mm above the block paving that would spoil the looks of the front, so I cut away 150mm of the slab towards the inside and put some footings down. Some builders use a lintel placed the whole width of the garage on either end to build the wall on. My outer brickwork would only be supporting the window above so I went for new footings using standard concrete.

The keep some original features I planned re-using the original oak pillars, decided to use timber fascia boards with the timber diamond shapes from the old porch, and to source the same tiles.

The work begins…. skip ordered and delivered the next day.



I removed all tiles and kept them safe just incase I could not get a same match and may have to source some reclaimed ones.


You can see over time the felt has had ponding, that’s where water collects and drips down into the fascia or wall instead of going into the gutter. Felt support trays have now become a standard so it will be vital to use them later on.


With all the tiles removed, I took a layer of felt off the porch to find that there was also a lead layer. It was very difficult to remove. I used the crow bar to slide under, lifted the felt off which was stuck down by bitumen (Tar). I cut the felt and lead into small pieces using the recip saw, the only way I could take into down. I should get at least £20-30 for the scrap lead the next time i visit the scrap yard.


Once the roofing felt and lead was completely removed I took the timber structure down.  I had to be extra careful when standing on the roof as all joists were rotten apart from the floorboards on top.


A few hours later most of the porch was removed. Each solid oak pillar must have weighed over 100kg. They were both bedding in concrete so I had no option other than to break away the concrete to get them out. One was completely rotten below ground level. Since I will be extending the porch slightly outwards I will be making a strip foundation to build a 3 engineering brick course to sit the pillars on.


I removed the concrete footings that the pillars were bedding in. It took some help, 2 of us to get them into the skip, really heavy.


On the garage side I cut the floor slab 150mm back so I could put some footings down. As the footings will be only supporting 11 bricks high I decided to make them 250mm wide, trench filled 450mm thick concrete with a re-bar from pillar to pillar so it also acts like a lintel.


Last time I mixed concrete myself for the bay window removal I used buckets to get the mix right. It was really hard work on my own so this time I opened up 2 cement bags at a time in a wheel barrow and shovelled in 4 spades per 1 cement directly into the mixer with half a bucket of water first. So much easier than carrying and tipping full buckets into a mixer. It took me approx 40 mins to do the left hand side, (1 ton of ballast Jumbo bag), and 20 mins the other side, (half a ton).


A few days later I had the engineering course down. Note I had placed 2 concrete blocks flat which will make the base of the oak pillars even stronger. To carry the air vents forward I used telescopic risers as before so I had to leave gaps.
You may also notice that I have used a mixture of 73mm bricks with standard 65mm bricks. This is because the 73mm engineering ordered were more of an orange colour that did not match the rest of the house. I had plenty of 65mm and just about enough of the 73mm bricks left over from the main extension. So 73mm orange bricks, 65mm red next course and 73mm red for the last engineering course. The orange bricks will not be visible as the block paving will be 2 bricks lower than the DPC. You can see it’s quite messy here.


I used my self-levelling laser to level 2nd course of engineering bricks. Spot on! Fixed the string-line and ready for the next layer. Fo the inner block work, below the DPC 2 courses of 73mm bricks were used to bring it up to the required level. To key in the bricks to the floor I drilled a couple of holes in the gaps of the bricks into the concrete floor and attached brackets taken from the wall starter.


I cut about a foot of damp proof membrane, tucked it under the DPC, put some mortar on top so it was ready for the 1st brick. I changed the mortar mix to 1:6 for the thermal bricks above the DPC and put wall ties into place.


Wall starters were fixed to wall, keying in the bricks took some time as 1 inch of the rear blocks had to be cut so they would fit flush against the wall. On the left hand side I fixed a timber batten just to keep the blocks going up plumb. I had to think of the window size and height and construction of the roof timbers above the window ledge, so I called it a day.


The next day I decided on a 4 section window with 2 openings on each side. I worked this out by taking into account the existing UPVC windows that were 65omm wide. 4 x 650 = 2600mm, the porch UPVC pillar to pillar is 2630mm so it worked out well. The height will have to be worked out once I have some new roof rafters in place. Wall ties were placed on every block around the openings.

Rough sketch

Planning the roof structure is vital before taking the brick to full height. The minimum pitch of the roof tiles will have to be taking into account here. My existing roof was at a pitch of 25 degrees, the redland tiles were below the recommended 35 degree pitch. I have found duo tiles that go to 25 degrees that are a full tile that have a groove to make them look like two tiles are joined. I will be using these. This means I can go for a standard breather membrane and lath construction. Otherwise I would have to put a lay of ply sheet over the rafters, nail a layer of felt, glue another felt over before fixing the laths and tiling.


When I completed the last course of engineering bricks the following day it rained. I did not cover the brickwork so water filled the holes on the engineering bricks. This water oozes out when the DPC was bedded in mortar that made a right mess on the face of the engineering bricks. I will have to use an acid wash later to remove the stains.

I first placed a dry run of the facing bricks with a 10mm gap mortar bed in between. This did not work as planned as there would be a 30mm gap at the end so I had to increase the gap slightly across the layer to keep the mortar uniform. I built up the corners, filled in the brickwork in between using a string line.  I then placed two battens on either side to give me a guide secured by some heavy concrete blocks. Now and then I would check the levels using the Stabila spirit level. The very small level I used to get the bricks flat. You can easily check if any are out once one brick has been levelled perfectly.


I only managed to lay under 100 bricks by 2pm although i took most of the morning to fix the wall starters, tidy up, and to move the bricks nearer to the work area. Building the corners plumb takes some time. I had to knock a couple of bricks from the rear to make the wall perfectly plumb.


The corner of the other side will not been seen as the side gate will be moved towards the front. I did not bother using a string line here, just the medium size spirit level to level the tops and a piece of timber to get each layer flush with the existing wall.


A few hours later I had it almost to window height. You may notice I have not filled the joints fully. I will be using white cement and silver sand to point the walls to match the rest of the front of the house.


I made a silly mistake here. I built up the left pillar 2 bricks wide, the right 2 and a half. I only realised 3 days after when viewing from the road. Having a skip too close just did not give me the room to stand back a look properly at the work I was doing.  I had to grind the mortar out and carefully remove the bricks without disturbing the rest. Half a day wasted.

The next step…. I will have work out the roof construction so I can find out exactly how high the final brick will be.


I planned using slightly stronger rafters, 125mm instead of the required 100mm to avoid the roof sagging over time under the eves over-hang. Also a 6×3 C24 very strong beam to support the roof up sitting on top of the pillars. Another supporting beam under the eves bolted to the pillar if possible.


I began by attaching the wall plate against the wall using M12 anchor bolts 120mm length. I marked 450mm centres where I would possibly fix the bolts. I first drilled a 10mm hole in the timber, placed the timber against the wall and drilled one end using s 12mm SDS bit through the timber into the brick. The This is the only way I could place a level on the top and do the same  on the other end. I could not fit the wall plate the same height the whole length since there was a concrete slab sticking out from where the balcony was removed.  I wanted an exact 25 degree angle on the rafters since the duo tiles have a minimum angle of this pitch to meet building regulations. I cut both oak pillars to the same height 2.2m as both were rotten. My idea was to put one into place so I could work the rest of the roof off this.


All the rafters in position. I used a string line to make sure they were all level and used trus clips with screws to hold everything in place. I will have to add a couple more anchor bolts to finish off the wall plate. Next job will be to get a pillar cut to size and in so it could bear the load of the roof.


I did not want the pillars rotting over time so I made a lead drain-off for both pillars just incase rain got under the posts. The lead also made the job look as if is been done properly. The DPC will be run under with a bed of 4:1 mortar.


I used a cardboard cut-off trace the placement of holes in the engineering brick. I copied 2 large holes on the oak and nailed some nails to key it in place. I drilled and screwed a very long bolt which will be bedded in concrete in the cavity to give it support.


With incredible difficulty and strength! I managed to lift one pillar on my own into place. It was free-standing until I got a long beam to temporally hold it in place with some clamps and screws. I had cut every rafter beforehand at the angle, fixed joist hangers at 450mm centres on the wall plate. I was waiting for the delivery of the main supporting 6×3 purlin which will be the main supporting beam. I will have to slot this in when it arrives.


The strong beam arrived same day so I managed to permanently fix everthing in place. I had to cut notches again in the rafters by removing one by one. Good job I used screws. I fixed an end beam approx 300m away from the other. I will raise this slightly by 25mm to provide an inwards slop to stop rain running down the side or perhaps screw a roofing batten onto it.


I removed the scaffolding and placed 3 bricks on each side of the posts. I then placed battens and a wider timber in the centre to see what the UPVC door will look like. You can see the diamond window on the oak door is not central. Oh Crap I made a mistake! Anyone else would have carried on however i’m only going to do this once, so taking half a day out to correct it is not that bad. I have already placed an acro so I can slide the post towards the right while I rebuild the brickwork on the left hand side half a brick inwards


The next day I fixed the fascia board 25mm above the rafters using 1 screw on each end as I was not sure if the first tile will be sitting at the same as the rest of the tiles.

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I put a couple of tiles in place to make sure the fascia board was ok. It seemed ok to the eye.


I nailed down the felt support trays leaving a further gap of 10mm so I could fix a UPVC fascia capping board later just in case. Each felt support tray i overlaped by 150mm at the joins.


I rolled out the breather type felt by using a battern placed underneath. Cut to length leaving some overhang. A few cloat nails towards the top stopped it from blowing away in the wind.


From the Marley website I found that the first lath should be fixed at 189mm from the edge of the fascia. You can see I measured from lip on the felt support tray as the fascia boord is directly under this. I nailed one end in using a 75mm long 2.5mm thick galvinised nail. The reccomended nail thickness is 3.25mm however I found it usually splits the laths so I went for a thinner size.


I used a string line to check the lath was plumb. The first row is really important as any distortion in the lath will be reflected in the tiles. I used a plastic spacer so the string would not touch the lath on both sides of the string to get it  Perfect! I nailed the lath over every rafter. I final check showed the lath had moved slighly in some placed perhaps due to the banging of the hammer. I should of nailed the nails halfway before fixing them permantley. Before the end of the day I found 25mm above the rafters did not allow the 2nd tile to sit properly so I will have to increase the height to about 40mm tommorow.

I also noticed 240 tiles that I had ordered will not be enough for the roof if i’m going to use a smaller 100mm head lap instead of the maximum 190mm for the Ashmore tiles. So much for asking a roofing supplier! They said use 18 tiles per m2 for a 6m x 2m roof.  18x 12m2 = 216 so I ordered 240 to be on the safe side. Using my simply calculation, 20 tiles wide, 20 tiles up = 400 less the 10 x RH and 10x LH 2/3 tiles = 380. 140 short in other words £133 @ 95p each.

To calculate the tiles I took the distance between the first lath to the top of the last lath. This was 1920mm. Divide by the headlap of 120mm gave exactly 16 tiles.


I made a guide 120mm the same as the overlap that I will use to position every lath equally. I made two of these just in case one fell down the scaffolding.

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All the laths took about half a day. Every third one I checked using a string line. At the joins I nailed the nails at an angle into the rafter so the lath would not split.

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I put down more tiles working from right to left leaving an 50mm overhang for the undercloak. The first tile was nailed and thereafter every third one.

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With a bit of help passing the tiles to me really sped up the progress. Also as I was not walking on top of the tiles they stayed in perfect cosmetic condition.

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Some edges of the Marley Ashmore tiles had rough edges that did not allow them to sit properly. I used a pincers to crack off the bits on every tile.

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On to the lead work now. I purchased a roll of code 4 lead 240mm wide by 6m long. Code 4 is thicker than code 3 by the way.  The minmum 75mm upstand against the wall just did not look right so I increased it to 100mm. This also would leave a 140mm overlap almost the same as the 120mm overlap on the tiles. I grinded out the groove using an engle grinder with a diamond cutting wheel. I was very dusty and noisy.

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I had an off-cut from the main roof that I marked ran through the groove, approx 25mm into the render to make sure the main lead will slide in without any difficulty.

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To prevent the lead pulling itself out overtime I fixed lead straps at every 3 tiles that I could fold over to keep the lead in placed.


I rolled out the lead ontop of a plank. marked it at the maximum 1.5mm and cut using a knife. The lead should be not be fixed at more than 1.5m lengths to avoid the expansion and constraction tearing the lead.

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Using the plank I bent over a 25mm lip. I mis-placed my lead beater so I used a flat piece of timber and rubber mallet.

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The fact the the groove was at 100m, I found a batten that was pprox 95mm by chance. Adding the thichkness of the lead it would sit perfectly in the groove. Instead of beating the lead I simply bent it over by hand approx 25 degrees same as the roof. To make the fold more percise I hit it a couple of times using the flat timber and mallet.

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I turned it over and made the whole length flat using the longer batten. I found if I used just the mallet to form it it left marks so I flat timber was much better.

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Completed lead run. You can see I kept the up-stand angled to approx the same pitch as the roof.


Taking the lead was tricky whilst on the roof. Best to get some help in. Once I had it in place it simply slotted in. perfect!


At the joins I overlapped between 100mm and 150mm. The end of the strap I bent over to secure the length. I cut the excess at 20mm.


The excess ends I trimmed down, folded in half and hammered flat. I did purchase some stainless-steel clips however they are more suited for fixing into the mortar gaps of bricks. Since my wall was rendered I had to use lead bullets instead.


A couple of strikes with a blunt chisel and hammer secured the bullets in place.


Lead work almost complete. Just a little bit that I will have to form, perhaps do a weld around the main roofs underclock.


Moving onto the porch floor. I had the same construction in mind, 100mm hardcore, 50mm sand, DPM, 125MM insulation, 100mm concrete slab, followed by self leveling compound.



It took a almost a full day to get to this stage. Sorry I completely forgot to take pictures. You can see I also added 25mm insulation around the edges to prevent cold bridging from the outside. Once I got the 100mm concrete in I decided to mix a couple of shovels of screed to assist leveling and to soak up any excess water from the concrete.




The next stage was to finish the brick work. I fixed a batten on the right-hand side to keep it level. I kept all bricks flush to the oak posts.


As I was going to the full lengths of glass on the doors I left an opening for a slightly larger letter box in the brickwork instead. I placed a metal support to support the next course of bricks.



Once the brick work was complete I asked my supplier about low profile sills for the porch doors. You can see I went for a stubby sill to reduce the risk of tripping over when entering the porch.

I will post a diagram of the design as sizes later.


The frames and glass were delivered the following week. Great service for Great Barr Windows. I decided to fit the window to secure the property first. I measure the sill overhang with the frame attached. 80mm. I decided to recess the frame 40mm away from the face of the brick work to match the rest of the property.


The supply the sill 100mm longer to allow for the over hang at the sides. I marked using a pencil and cut using a standard wood saw. Note make sure you mark what area need to be removed as I did make a mistake cutting once.


Sill fitted on top of a 1-6 mortar mix. I always run a bead of silicon to prevent any water entering the inside if for example jet washing the windows.


Window frame in place. I will have to fix the frame to the sill from the top side using screws.

To fix the frame to the brick work I fixed 3 screws on each side of the window. Notice I placed plastic packers to allow the screw to hold tight. Wihout the packer the UPVC plastic will bend if the screw was driven in too much. At this point I noticed perhaps I had the window made slightly too small. Instead of going for a 5mm gap on each side I shpuld of just taken 5mm off the dimensions.


You can see the self threading/cutting screws cut the thread into the brick, so much better than the old sleeved frame fixtures. I found you have to use the correct sized drill-bit (5.5mm) to there is enough brick left to the screw can cut the thread.

Almost complete. I will silicon the edges once I have pointed the brick work. I have purchased some silver sand and white cement. My bricky mate said I should use some hydrated lime however I will test a spot using some plasticiser as I do not want the pointing too white. Moving onto the porch doors and windows….


I marked and cut the stubby sill for the doors like above. Notice I have not left much of an overhang. This is due to keeping the frame recessed approx 10mm the same.


I placed a bed of mortar on top of the bricks and made sure all the holes in the engineering bricks were also filled as I will be screwing a couple of fixtures to hold the sill in place.


As before a bead of silicon to prevent drafts and water ingress.


I had to trim the corners of the frames to ensure any joining UPVC fitted flush and tight.


I  placed the right-hand side window in position just to check spacings. When I measured up I asked Greatbarr Windows to take 5mm off all dimensions. This left abit too much gap on one side so I added a knock-off (spacer which clips onto the window profile) to fill the gap instead of using a very thick sealant.


I added 2 blue spacers as the mortar bed under the sill to I could check the top alignment,


The top was not in line.  I was supplied a knock-off which I assumed was to fill this gap so I added one to the window frame. MISTAKE: I later found the knock-off usually runs the enitre top of the frame to strengthen the frame when I found the lead was  25mm off-alignement when the glass was fitted. As I had already fixed the frame it will be easier for me to get the glass for the doors re-leaded.


I found when installing my main extension patio doors than had really large planes of glass the spacers did not quite sit flat so I added a very thin spacer before adding the main blue packer/spacer. This would also ensure the weight is distrubuted evenly onto both sides of the glass.


Moving inside….



The old garage floor was cleaned and ready for insualtion. As I did not want to lose much floor-to-ceiling headroom so I decided to use 75mm closed-cell instalation such as Celotex, Xtratherm etc.. This would save me 50mm if I went for the standard 125mm expanded ploystrene insulation. I could directly placed tounge& groove floor boards onto the insulation however as it was a garage before the floor had a slope towards the outside. To level almost a 50mm slope would involve some screeding. In the end I decided a 65mm screed with screeding fibres to add strength.


Before I put the damp proof membrane down I scraped off any flacky paint and salt off the DPC. I brushed on some stablising solution as I already has some left over when I treated some damp walls before plastering. It really stinks so I got my cool-man cousin to do this task! I then mixed some mortar 1:4 with plently of waterproofer to fill any gaps in the brickwork.


Where the walls were facing the outside,  25mm insultion was placed on the perimeter to prevent cold bridging. I had to redo this with slighy higher insulation as I did not account for the slop in the floor.


The heating pipes for the radiator were placed into conduit and wire tied together. I marked a guide line using the laser at the lower end of the floor. It was approx 110mm above the insulation. I will have to keep the thichkness approx 95 mm here.

Mixing the screed. As it was a small area that needs to be screeded I decided to mix it myself instead of ordering self=levelling liquid screed. It has to be semi-dry with just the correct amount of water to hold a ball when compressed in the hand. If its too dry it will crumble. If it right it should break into 2 pieces when broken apart. I added screeding fibres, a handfull in every cement mixer mix.

Mixing was tricky in a standard mixer. When the water was added if it gets mixed too much the screed will turn into balls. So I let it dry mix before adding the right amount of water. I used a 1 cement to 4 screeding sand mix. I had a small pot container that i used to gradgually sprinkle 5 lots of water from a bucket rather than adding the water in one go. In the end I used just under 1.5 tonnes of screeding sand.


While I was waiting for the screed to dry I thought of finishing some loose ends on the outside. I purchased some Cuprinol garden shades black-ash paint for the cladding under the porch eves and oak pillars. I did not go for a standard black paint as I perfered the grain to show through the timber to provide a real natural wood look.

Self levelling: For this task I sealed the screed withg a thin layer of self-levelling compound. I did not pay much atension to getting in level, just to seal it. The next day I applied some PVA to prevent the floor soaking up the water from the compound to allow the compound to flow better.



I purchased a spiked roller which has spikes that help to remove any air from the compound and perhaps assist in levelling the compound by rolling it over the compound.







I looked around for white pointing in tubs and could not find any available. After some research I found that silver sand (also known as play-sand at some builders merchants) is used together with white cement and hydrated lime to obtain the white pointing or mortar.


Mixing dry: the colour did not turn white.


After adding the water it soon started changing. I only mixed enough to do a small section at a time.


It can be messy and very time consuming. I weather-struck the pointing to match the rest of the property.