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Advice on Oak Pergola

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porker

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I am after some advice regarding costs of building versus buying a green oak pergola. My wife is getting to the end of an epic hard landscaping project in part of the garden and wants a pergola. I agree with her and like the look of green oak with pegged mortice and tenons . I've researched a bit about building one so understand how they are constructed but am not sure if buying a kit would be cheaper then making one myself. One of my concerns is cutting the mortices. I don't fancy doing them totally by hand and a chain morticer is an expensive bit of kit. Would I end up spending around the same making one myself from scratch as buying a kit?
The other issue is that what I want is an odd shape so a kit may not be available that fits what I really want. It is to fit into a corner of the garden and opposite the corner (which is knowhere near 90 deg) is a quarter of a circular patio so it is sort of square(ish) with an arc out of one corner if that makes sense. Probably around 3m x 3m.
Any advice would be welcome.
 

MikeG.

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Why not chop them out with a chisel? Green oak is a delight to work with. It's a little like chiseling cheese, or a raw potato. It couldn't be easier.
 

Blackswanwood

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Hi, I went through this thought process a year ago and opted to build my own. I didn’t get a chain morticer but I did buy a steel framing chisel that can be hit with a lump hammer. It’s knackering but great fun. I also bought a heavy duty circular saw which made a big difference.

I saved two thirds of the cost but invested a load of time doing it. I’m glad I did and plan to go on and make another one.

Cheers
 

porker

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That's interesting Mike. I've worked on seasoned oak a bit before (modified staircase) and imagined it would be blisteringly hard work even on green oak hence the talk of chain morticing. With the right chisel is it really not that hard (the wood I mean not the skill to do it)? I'm a fairly fit 51 y.o.

This part was the bit that was most daunting to me. The design I am comfortable with and maybe even cutting the M&Ts. Planning for 150x150 posts and similarly chunky rails. Also considering raising the posts off the ground and see there are different ways to do this. Would you recommend doing this and should I use metal brackets or raise them on stone?

Thanks Blackswanwood - I never expected it to be easy as the timber itself is heavy. The time is another issue as I would like to do it, but I am also refurbing a large house and doing 90% of it myself but sometimes there is a project I would prefer to do and I expect this would take some time.
 

AJB Temple

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I have a chain morticer. If you are anywhere near Kent I can lend it to you.

You do not need a chain morticer to make a small structure like this though. They are quite scary tools and really only worth the investment (even used) if you are doing a lot.

You will be fine with drilling the waste out and then using a chisel to square up.

Oak is only soft if it is truly green. I.e. fairly freshly cut. If it has spent a few years in a yard it can be pretty hard, but don't let that put you off.
 

AJB Temple

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By the way - you might think 150mm posts are "chunky" but they are not. If you want it to look chunky you need 8" posts.
 

Blackswanwood

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Re your question on raising off the ground I would suggest you definitely do need to do this. I toyed with using two brick high pillars but ended up buying some staddle stones.
 

MikeG.

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porker":35ic1ikw said:
That's interesting Mike. I've worked on seasoned oak a bit before (modified staircase) and imagined it would be blisteringly hard work even on green oak hence the talk of chain morticing. With the right chisel is it really not that hard (the wood I mean not the skill to do it)? I'm a fairly fit 51 y.o.
Honestly, if it's green an ailing 75 year old would chop out mortises pretty easily with any old chisel. It's the most fun woodworking you'll ever do.

Also considering raising the posts off the ground and see there are different ways to do this. Would you recommend doing this and should I use metal brackets or raise them on stone?
I would cast a steel foot into concrete to keep the bottom of the post well clear of the ground. If you get a bit fancy with the design you might then lay some bricks or stone, or even cast a staddle- stone yourself, in situ. The easier way of covering the gap, though, is to put a little sacrificial oak skirting around the bottom. This looks great, but only lasts a few years before needing replacing. Either that or simply cover the gap with planting.

I'd be very cautious of using 6x6 timbers for a pergola, and 8x8 .....well, if you own Hampton Court then maybe, but for a normal size structure it would be overly large. One of the mistakes people always make with designing stuff in oak is to make it too heavy-looking, in my view. I see non-structural posts inside little cottages made of 8x8, where 4x4 would be more appropriate. I tend to use 6x6 for structural elements, and 5x5 for intermediate posts, with some open studwork of 4x4s. Ancient buildings had some big structural pieces on show, but the secondary timbers tended to be much smaller. I made a nice oak pergola in my last property and used 4x4s. I was supposed to be doing an oak pergola here this year, but I doubt that will happen now.

The two things I would stress about designing a pergola would be to allow a lot for the area the plants will take. If you put the posts 6 inches away from the path you'll need a machete to get through in a year or two. I suggest 2 foot each side of your path to the inside of the posts as a starting point, and three would be better. The other thing is to design your braces carefully. It is the arched bracing which will be the main feature, and pretty much all you will see of the pergola once the creepers and climbers have got going.
 

porker

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Thanks for all the responses. They are very welcome. Regarding the post size, that is a very fair point and something I may rethink. I am starting to draw it up now and as you say it possibly looks a bit 'chunky'. I'll do another sketch with reduced beams. I won't be the final decision maker anyway :)

AJB - thanks for the offer. I am based in Bucks but am now thinking maybe cutting with a chisel is something I'd like to try. I hadn't seen steel framing chisels before and they look like something I 'need'.

I'm still at the design stage and need to think about any footings now before stone is laid. Casting concrete with a steel foot is no problem.
 

porker

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Mike, I agree, the braces seen to make or break the visual impact IMO. These I want to get right and looking at a slight curve which I assume I can cut on my bandsaw.

Will investigate a source for the timber now and push on with the design. May well pick your brains once I've moved this on a bit more.
 

Myfordman

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I used curved braces made with the waste from the concave cut, PU glued and screwed back on the top to give the convex curve.
Been up 20 odd years with no problems.
 

AJB Temple

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You do NOT need framing chisels. Trust me - if all you are doing is a pergola (versus a house, say) then what you need are some wide chisels (eg Ward etc) off eBay or similar. I have, 1", 1 1/2" and 2" all old Ward, with wooden handles and brass rings as you will be belting them with a hammer. I doubt if I paid more than £5 for any of these old chisels.

Also get an old pig sticker chisel. Very good for getting into the corners of mortices.

I doubt you will use slicks - you certainly do not need to buy them until you gravitate to big stuff. I have framing chisels and slicks, but what I use most is the old Wards. Easier to handle and far less tiring.

I would get a 1 lb and a 3lb Thor hammer with copper one end and hide the other end. This is for belting the chisels and encouraging joints into place. I also find a 5lb double leather faced hammer very useful, but overkill for your project.

Buy some good quality spade bits for roughing out the waste. You can use auger bits, but I find they tend to pull hard into green oak. Auger bits, if used a lot in high torque drills, bend far more easily than you might expect. You can also route the mortices but it is much slower as the waste does not clear easily.

If you use a powerful corded drill (I often use a 110v high torque Makita) and a bit binds, then the drill will whip round at lightening speed. Be aware of this right from the start as it really hurts. DAMHIK.

Get your act together with sharpening. It wants to be simple and easy and non fussy as you will be sharpening chisels a lot.

Get the biggest circular saw you can lay your hands on. This saves a lot of time. Don't forget an 8" diameter saw will only cut to just over 3" depth.

Electric planer eg the wide Triton one I reviewed on this site, will save you hours of prep on green timber. Cheap and very effective. Much faster than (a virtually indispensable) 4" wide belt sander.

Roundwood (Google them) sell tapered and straight granite staddle stones with steel pins set in. Usually a fairly sensible price.
 

porker

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You do NOT need framing chisels. Trust me - if all you are doing is a pergola (versus a house, say) then what you need are some wide chisels (eg Ward etc) off eBay or similar. I have, 1", 1 1/2" and 2" all old Ward, with wooden handles and brass rings as you will be belting them with a hammer. I doubt if I paid more than £5 for any of these old chisels.

Also get an old pig sticker chisel. Very good for getting into the corners of mortices.
Thanks - I'll look at what I have as there is a good chance I have something suitable. My FIL recently passed away and I have yet to look at his tools (due to the lockdown) but I know he also had a fair collection of hand tools and may well have something there.
I'll keep an eye out for a good pig sticker as I know I don't have one.

Buy some good quality spade bits for roughing out the waste. You can use auger bits, but I find they tend to pull hard into green oak. Auger bits, if used a lot in high torque drills, bend far more easily than you might expect. You can also route the mortices but it is much slower as the waste does not clear easily.

If you use a powerful corded drill (I often use a 110v high torque Makita) and a bit binds, then the drill will whip round at lightening speed. Be aware of this right from the start as it really hurts. DAMHIK.
Well aware of this due to experience unfortunately so will be careful. I have plenty of reasonable spade bits. Also have some that pull in which is great drilling joists but a bit fierce on other applications.

Get your act together with sharpening. It wants to be simple and easy and non fussy as you will be sharpening chisels a lot.
Yes have this covered with an oil stone and a couple of decent diamond plates. I understand oak can be hard on chisel edges

Get the biggest circular saw you can lay your hands on. This saves a lot of time. Don't forget an 8" diameter saw will only cut to just over 3" depth.
I have the standard Makita circular saw and have seen people cutting from both sides. I guess this also depends how thick I am cutting. Will need to keep an eye out for the bigger makita or borrow from my mate who has one :).

Electric planer eg the wide Triton one I reviewed on this site, will save you hours of prep on green timber. Cheap and very effective. Much faster than (a virtually indispensable) 4" wide belt sander.
Yes, very tempted by that and looks a great tool. Have been looking at purchasing a PT for some time but as my workshop project is way down the line I try to avoid workshop machinery and use tools I can take to the job. Interested to know if it is useful for flattening boards generally as I have other projects in the house where I need to make tops for built-ins and wanted to buy rough sawn.

Roundwood (Google them) sell tapered and straight granite staddle stones with steel pins set in. Usually a fairly sensible price.
Thanks, I'll take a look at those. I am looking at the options for this at the moment.
 

MikeG.

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I'm with AJBT on this one, but a 1-1/2" chisel and a big mallet are the upper limits of what you need, presuming you have a normal set of bench chisels. Oh, and if you hit a chisel with a hammer, I'll send Carruthers around with a horsewhip....... :lol:
 

AJB Temple

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I agree really. The reason I like to have a two inch chisel is that when I mark my mortices in framing oak, before drilling out the waste, I bang to the line all round with my chisel to delineate the cut to point. It helps me avoid drilling out too much. Quite often I will do mortices 2" wide by 4" long and that is 6 bangs with the mallet :D
 
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