My Garden Room Build - 9m x 4m

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Aug 2021 - Pergola stage 1

I did the pergola in two stages, three if you include the planning stage which I explained in painful detail earlier. The multi stage approach was really to work around the weather and material supply issues. Doing the pergola stuff (not really priority item) to fill in time, and then moving to higher priority tasks when weather or material stuff permitted. Great in theory but the staged approach did lead to one decent sized mistake which gave me a bit of head scratching later on.

Stage 1 was placing the posts in situ (plumb in both axis) and marking up the position of the horizontal cross beams, which will be joined together with half lap joints.
Stage 2 was cutting the half lap joints in the posts and assembling the structure

Stage 1 and stage 2 were I think 6 weeks apart. Marking and cutting should not be 6 weeks apart. No matter how clear your marking out is, future self will misinterpret it one way or another. And I did. More on that later.

Here is a reminder of the design:
pergola design pic A.jpg

I used some self install groundscrews as the foundation for each pergola post. These cost I think £20 each + £10 for a 'U' bracket per screw, then we have £45 for a T bar installation tool and £100 for delivery, so about £400 for 9 screws delivered. Not exactly cheap but with expensive Cedar I didn't want the posts sitting in the ground and rotting either so decided that it was a justified investment. It was also a bit of a learning experience - one of the reasons I wanted to go that route.


The Cedar
It does look nice....

....and smells even better

The screws
Following on from the advice I received on a separate thread I bought some Reisser screws, and I'm really happy with them. The big ones are 8mm thick and are a thing of beauty.

Hugeness (not as big as the groundscrews though):


Here is what I ordered with prices, I was quite happy with the costs (I got them from ironmongery direct)
screw order.jpg

Marking out
I used maybe 15 or 20 clamps to hold all the posts and cross beams in the right place, just so that I could mark up the posts ready for cutting. Lots of messing around with spirit levels, up and down ladders, adjusting things and readjusting things, until every single part was plumb and level. Then I could mark up the half lap joints on all the posts.

The mistake happened on the posts at the near edge of the decking (not the posts adjacent to garden room). These posts receive two cross beams, like all the other posts do, but these posts do it at two different levels. This is where my marking up wasn't clear enough for future self. I ended up cutting the tops off these posts (just above the lower cross beam) instead of adding a second layer of half lap joints for another 'upper' cross beam - this meant the posts were too short and where only long enough to support the lower cross beam.

This is problematic post
mistake on post.jpg

The posts are £125 each and on an 8 week leadtime - either way, replacing them wasn't really looking like a great option.

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Oct 2021 - Pergola stage 2

So having measured and marked everything up over a month earlier, I started now cutting the posts and assembling them into a pergola shaped object. The half lap joints on the posts were cut using the mitre saw and were really easy to do, the Cedar is really easy to cut.

One hit with a hammer and it needs almost zero clean up with the chisel

All the half lap joints done - I also added a little chamfer on all edges which is pointless but I really like it...

After OSMO oil

With the OSMO oil you really need to wipe off excess with a rag, I didn't first time around and it was sticky for days. I used a rag next time and it dried in a day. Also, the oily rag is dangerous so don't store near your kindling 🙃

Mistake and bodge fix
So because I accidentally cut 2 of the posts too short and I didn't want to wait 8 weeks for new ones (or pay £250) I decided to extend the posts using another piece of cedar and construction screws. I will later mask my error with some cedar cladding around the base of the post.




Post section finished, spars are next up

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Oct 2021 - Pergola stage 2 continued...

I was advised by a few people that notches on the spars can reduce the strength of the structure and therefore not necessary - but I did them anyway. I did compromise and make them quite shallow (25% of the wood thickness). I think I just prefer the look of them when they are notched, they look more integrated rather than sitting on top.

It turned out the my mitre saw's trenching feature did not have enough thread on the bolt to cut at the depth that I wanted. I have encountered this issue before and I really don't know why they don't come supplied with a bolt long enough to trench at any depth in the range of the saw. Anyway, I modified the little swinging platform thing by CA glueing a M10 nut on top. This allowed me to cut a very shallow notch in the spars.


One thing I noticed is that this little platform does flex a little bit if you push down on it, so when trenching you get much more repeatable cuts if you take care not to force the saw down into the wood and be very gentle with it instead. By doing this the trench cuts were coming out really clean and consistent but they weren't until I figured that out,

Spars on top





Views from inside (and the future...)


Overall I'm really happy with how this came out, it completely changes the feel of the garden. It also creates a sort of L shape, or is it a U shape, that makes a bit of a bridge between the garden room and the house, it links it all together. Once I get the little screen things on the back it will feel super secluded. Probably.

Are you using clear wriggly plastic sheets on the roof...........

Fetching coat and ducking to avoid hammer.. Looks good really!
Funny you say that Rob, I thought the prices might be even higher. Having looked at bog standard b and q type trellis stuff recently that was working out quite expensive anyway and I didn't really like it. I quite like the look of some of the screenswith envy stuff, although it would be nice to see it before buying.
Just took another look, I think some of the products are like you say very premium / expensive but I think others are pretty good on value. For example a 1200mm x 600mm (5mm thick) screen for £45 seems pretty good to me, and £60 for 16mm thick option. But then you see fence panels at over £500... so as I say some of it does look quite high end but other products are certainly more 'accessible'.
Sep 2021 - Media Wall Internals

Going back in time a bit here because I put all the Pergola stuff together, which started early but ended late, not sure that makers any sense, anyway...

This stage was all about the complex wiring inside the back wall where the TV was going to be mounted (speaker wiring mainly), but this wall also needed to support a TV bracket so everything had to be quite precise.
I had 3 speakers in front wall, and 4 in ceiling, and all the wiring for the ceiling speakers were routed inside this wall through a cable conduit which had an exit at the bottom of the wall.
It turned into a bit of a ball ache to be honest, and if I did it again I would design the walls around the speakers and not the other way around.
Mistake #1
The main mistake here was not really understanding how the speakers mounted into the wall before I received them - the constraint was that they need about 50mm of plasterboard cavity all around the edges so that some plastic lugs can be twisted into place and grab the wall from behind. The placement of my speakers was such that I couldn't accommodate this air gap all around - one edge of the speaker always ended up tight against a stud. It was fine in the end as I was able to attach it firmly by using only 70% of the lugs but not ideal.

I am glad I took millions of photos with a tape measure in the picture so that I knew exactly where every single wire was. This turned out to be a critical step when drilling holes for the TV bracket and knowing where all the safe zones were.

initial planning with all the cavities cut out for speakers, cable conduit and power socket

speakers arrived


later stage once all the speaker wire was in place

one of my million measurement photos

rockwool placed behind the speaker (acoustic reasons, as per Polk guidelines)

all 7 speaker wires jammed back inside wall temporarily - I will dig them out later after plastering

Oct 2021 - Plasterboarding and ceiling insulation

These two things seemed to happen together, not sure why, I was working a bit randomly for some reason.

Ceiling insulation
Tricky part with this was cutting cavities for the lights and speakers. I could have made things a lot easier by just cutting big holes out that went all the way through the PIR but that would have a created a non-air-tightness situation. This is only really a problem for me because I opted for a vented cold roof design, which means I have airflow passing above my PIR. If I have holes all the way through the PIR it means air can in theory flow into the room space if it can get find a way past the interfaces between plasterboard and speakers / lights.

So I had to perform lots of intricate 'limited-depth' cuts which really slowed things down. I found the best way was to make lots of knife marks and then hit it with a chisel to carve out the cavity. Some of the shapes I had to make were quite complex.






white wires are speakers, grey ones are lights

vapour barrier, stapled to joists


laser was handy for finding studs quickly

In the end I paid somebody to do the ceiling plasterboarding as I just thought it would be a nightmare on my own, and the plasterers did it all in a day so probably way quicker than I would have done it

Oct 2021 - Plastering and Flooring

Got a quote for £2800 for plastering and another for £1000. Seems to be a pretty wild range. I went with the cheaper one, and the overall finish was fine but the customer experience wasn't as they left behind all the plasterboard waste (including two full sheets which they didn't use!) which may or may not be normal practice, but either way it bugged me quite a bit.

In terms of flooring we couldn't decide between the Wickes laminate and the Wickes Vinyl stuff, so bought both and I did the office side in Vinyl and the workshop side in laminate. I actually prefer the laminate to the Vinyl, which was actually cheaper. I did look in places like John Lewis and Howdens also but honestly couldn't see why I was paying 3 or 4 times the price of the Wickes stuff. Maybe time will tell.

I acquired the below samples and quote from Howdens - engineered stuff was much more expensive than laminate, and honestly, although it looked different, it looked no better (to me) from the top, which is the bit you see. The laminate was basically identical to Wickes stuff from what I could see, just more expensive. I am not having a pop at Howdens, just passing on my thought process. If I had infinite cash I would probably have chosen the engineered stuff, just because its 'real' wood, but at the end of the day if it doesn't actually look or feel any better on a day to day basis then its hard to justify.

Anyway, here are some pictures.

Wickes laminate stuff

Vinyl option in office





Laminate stuff in workshop side



both options were fast and easy to fit, and took maybe a day each. If you knew what you were doing you could probably do them both in a day.

haha, the sockets are all hidden behind the wall at this stage - they will make an appearance soon, providing the measurements we took are accurate....