Pergola build

[ihadablackdog]

Ah, a jigsaw, why didn’t I think of that! Now you explained it I know what you mean, so yes, the notches should now be easy!!!!

Do you have any advice on fixing the post bases to the slabs? They just need one bolt/screw etc and my current thinking is a chemical anchor or concrete screws (only found they exist the other day).

[ihadablackdog]

Thatcher's Gold and living in Devon? Nothing like a stereotype then?

I’ll deal with that when I’ve taken delivery of my brand new combine harvester

[Pondrew]

Do you have any advice on fixing the post bases to the slabs? They just need one bolt/screw etc and my current thinking is a chemical anchor or concrete screws (only found they exist the other day).

What are the slabs laid on? If it's just sand/ soil or anything that's not concrete or mortar, I would just use a decent length and size rawlplug and screw TBH. If there is nothing under the slabs to fix into then you are only anchoring into the 50mm concrete of the slab (presuming they are concrete) so anything else is a waste. Concrete screws are more for blockwork, I don't think they will drill directly into a slab, although I've never tried. The secret is A) drilling a correct size hole for the plug so it fits fairly tight and B) using a screw that is as tight a fit as possible into the plug. Most rawlplugs (other brands are available ) will give the minimum and maximum size of screw recommended. Go for the maximum, or even the next width up, then you should get a nice tight anchor.
For extra piece of mind you could squirt some Gripfill (don't use solvent-free though it won't work outside and is crap anyway) on the underside of your bases just before screwing them down. The slab and post support need to be clean and dust free though. This will also help level any undulations in the slabs if they have a textured finish.
As you mentioned earlier, don't use anything that expands (eg rawlbolt), it will just shatter the slab as soon as you tighten it.
HTH

[ihadablackdog]

Thank you.

The patio was laid on top of a previous patio from what I can see at the edges. No idea what is under that, so it’s slab, concrete, slab. I suspect the concrete between the two slabs is just dollops and not a complete covering.

I was thinking of getting something long enough to also go into the bottom slab for a bit of extra strength.

I’ll rule out concrete screws.

Will the pressure from the screw going into the plug not crack it? I guess it’s just molding the plastic but there will be a bit of sideways pressure. I could test though, I have a spare slab.

This is the type of thing I was thinking about (not necessarily this kit), although I only need about a bolts height above ground or I’ll need to drill a hole in the bottom of the post if it sticks out too much https://www.screwfix.com/p/rawlplug-r- ... tid=387237

[Pondrew]

If you have more masonry underneath your slabs that's great (the more masonry the better in my experience).
You won't break slabs with nylon plugs, unless you are fixings very near the edge but anything will crack them then.
Those chemical fixings look more than sufficient but I've never used anything like that (too much faff and I'm a cheapskate)! They look like bolts with nuts; how will you sit the posts in if there is a stud and nuts sticking up? You would have to then drill out a piece of the bottom of the post to create a recess? If that's the case it's a lot of faffing about (as you can probably tell by now I like things to be easy and with minimal faff).
These are good for a deeper hole: https://www.screwfix.com/p/easyfix-fram ... pack/19356 and they come with screws to suit.
Whatever you use, just go steady drilling through the slabs. A percussion drill (hammer drill) can crack slabs if you go too mad at it. I have a professional hammer drill which has quite a bit of "hammer" so I just go really gently and at slow speed. I have drilled literally hundreds of slabs (used to often fix our work equipment to them) and never had an issue so they are quite resilient but are relatively thin.

[Pondrew]

double post doh

[ihadablackdog]

These are the post bases we got: https://ozcobp.com/product/6x6-post-base-ls/

As you'll see, they are from the US and feckin' expensive! Got them through Amazon and shipped from somewhere in America to here in 6 days. We had 3 of these, and 1 pack of the "s" hangers which has 2 in it.....weighed a tonne, its real heavy stuff.

The centre hole is recessed, and the actual bit that the post sits on is raised a few mm off the ground, so its got a bit of a standoff to help water drain away. A bolt might just fit but it would be tight, hence having to set the chemical bolt carefully...and as you say, thats a faff and doomed from the start. Technically I could just drill a wide hole in the bottom of the post for a recess, but would rather not.

I read somewhere to avoid drilling closer than 4 inches to the edge of the slab.

So those screws have potential. The centre hole is 16mm so i'd need a big washer or see if they do wider screws...looks like 10mm are biggest in that range. The base also has 4 separate holes I could use instead which are 8mm, so would fit perfect, but would I be ok drilling 4 holes so close?

Forgot to say earlier....will take pictures when its done! If I'm happy with it, plenty of pictures! If its sh1t, then probably just one blurry picture

Now I have the actual post bases, if the rain stops, I'm planning to go out this weekend and work out where to put them....possibly even fit them this or next weekend.

[Pondrew]

I read somewhere to avoid drilling closer than 4 inches to the edge of the slab.

Sounds about right to me. Your posts will be where your posts need to be, so if any are near an edge, just be really careful drilling. As you should be going down through more masonry they should be fine once drilled. You won't break a slab with nylon inserts (plugs) after they have been drilled. If any don't get a good "bite" then maybe go down the chemical anchor route.

So those screws have potential. The centre hole is 16mm so i'd need a big washer or see if they do wider screws...looks like 10mm are biggest in that range. The base also has 4 separate holes I could use instead which are 8mm, so would fit perfect, but would I be ok drilling 4 holes so close?

Either would be fine as long as you go steady drilling the slabs. The advantage with four holes is you can "level" the holder in four planes with the screws to get your posts as vertical as possible. If you wanted to just put one centrally these penny washers are the way ahead. 6mm hole and 18mm overall.
https://www.screwfix.com/p/easyfix-stee ... pack/413ft

[ihadablackdog]

[Pondrew]

I can't wait to see the pictures

[ihadablackdog]

Decided to go with the chemical anchor system in the end. Doing this way gives me a tiny bit of wiggle room if I’m a smidge out, the screw method would need to be mm perfect to get all 4 holes for the base spot on....and I don’t trust myself.

So fitted the studs today. Got half way through the first hole and my 20yr old hammer drill battery died.....so went and borrowed my neighbours Makita SDS drill....holy s**t, that was like a hot knife through butter! The stuff sets really quick and ready to use in about 3hrs, but I won’t be doing more until next weekend, so plenty of time for it to set.

Hope I did it correctly....too late now

4BB48561-A521-40A6-9961-78F6B9EEC17D.jpeg (262.08 KiB) Viewed 483 times

76118DD2-C780-4E1D-8064-5C99D6CE3698.jpeg (255.09 KiB) Viewed 483 times

EC7374DB-3930-43E6-91C5-684CBEC088E2.jpeg (289.36 KiB) Viewed 483 times

4DB182E1-E9CC-42D1-8094-AA0E160244B7.jpeg (151.64 KiB) Viewed 483 times

[Pondrew]

No going back now

[ihadablackdog]

True! Wood should be arriving this week (timber yard dicked me about but came good eventually...as long as they deliver!).

Going to notch the rafters, but the rear notches are going to be 45 degree's, so cant use the jigsaw method unless I plunge cut, which I don't think is a good idea. So going to use the circular saw method on those....however:

Its a 6" board ontop of an 8" board. I was planning on notching out 3" of the top board, but circular saw only goes to just over 2", so do you think 2" will be enough? I could notch out the beam an inch or two, but don't want to risk weakening that, and that would double the number of notches I gotta do...already looking at 30ish!

Going to screw them down from the top, looking at 200mm screws (I bought 140mm but not sure if they are long enough now).

Looks like one of my side studs is about 5mm out. Got some play with the post bases so should be able to rectify, but I'm thinking 5mm shouldn't really mess up the angles, considering the overall size....hopefully I'm just being over critical!

[Pondrew]

Its a 6" board ontop of an 8" board. I was planning on notching out 3" of the top board, but circular saw only goes to just over 2", so do you think 2" will be enough?

2" sounds fine, as there will be more 'meat' so less likely to get any splitting in the future.

[ihadablackdog]

Thanks. 2” it is then.

Weather looking ok for the weekend onwards so should be good to go!

2nd of my 45 degree angled rafter hanger due today/tomorrow along with various other bits and bobs this week.

I’ll be much happier when I’ve got the posts up and supported.

I’ll be even happier when it’s finished