A couple of questions relating to pergola construction

[kissinger]

As per title:

1) What do I need to treat the wood with, to make sure the pergola lasts? I assumed just a wood preserver, but apparently you also need a ‘topcoat’ of something. I want a completely natural look, and I don’t want anything that needs to be recoated quickly because it will be difficult to do when built. I don’t mind doing as many coats as is necessary and using multiple products if necessary, but if you can recommend specific products that would be great.

2) What should I fix the uprights to? I’ve included a photo of the area so you can see what I’m working with. These 60mm thick slabs are sitting on 60mm sand and 150mm compacted MOT1 hardcore. Crucial thing is the wood can’t be sitting directly on the slabs because of the risk of water damage, so I will need some kind of elevated bracket big enough for 150x150mm posts. I also don’t want anything very conspicuous. Has to be fairly discrete. I was thinking something like this, but would that be okay directly on a slab? I'm only having posts (3 of them) at the far end of the patio. The other side will be fixed directly to house wall, so it's effectively a lean-to pergola).

Thanks in advance for any help.

 

[^woody^]

1. Use tanalised timber.

2. The ground.

 

[kissinger]

The timber is already bought in, so what I’ve got is it. It is pressure treated though.

I know I need to fix to the ground! The question is with what do I keep it fixed to the ground that won’t allow water to get to the timber.

 

[Why Not Indeed]

Some relevant reading here:

Concrete fence posts for patio roof?

I am thinking of building a covered patio attached to an outbuilding in the yard. I am planning to use polycarbonate roofing sheets, and frame it is pressure treated wood. For the posts, I don't want to use wood, because they always rot at the bottom, so I was thinking to use concrete fence...

www.diynot.com

 

[kissinger]

Thanks, but that solution (concrete posts) would spoil the look. I'm really just deciding between (1) attaching the wooden posts to patio slabs or (2) removing the slabs/sand/hardcore in question and pouring in concrete, and then attaching to that.

 

[mrrusty]

These sort the problem. https://www.toolstation.com/post-ba...KXe3dOJJ5eMKJ8YUt8QaAqbCEALw_wcB&gclsrc=aw.ds

 

[foxhole]

These sort the problem. https://www.toolstation.com/post-ba...KXe3dOJJ5eMKJ8YUt8QaAqbCEALw_wcB&gclsrc=aw.ds

Has 150mm posts .

 

[foxhole]

These offer discreet fixing .

Simpson Concealed Post Base 89mmx89mm Cpt44z | Low Prices

Shop Simpson Concealed Post Base 89mm x 89mm Cpt44z at Tradefix Direct. Wide range of products at low trade prices. Bulk quantity discounts available.

tradefixdirect.com

 

[mrrusty]

Has 150mm posts .

Not sure why you need 150 posts for a pergola, but yes, I missed that - similar are available for 150mm

 

[kissinger]

Yep. Looks like a good solution. I will buy the 150mm version.

 

[freddiemercurystwin]

Yea 150 is massive overkill.

 

[kissinger]

Yes, structurally, but I'm going for 150 for aesthetic reasons.

 

[kissinger]

Sorry, one last question about this: regarding the finish, would a combo of wood preserver with a topcoat of Sikkens Filter 7 (which is also a stain) be sound, or should I also add a coat of Sikkens HLS prior to topcoat?

 

[^woody^]

You can get metal post bases that are either screwed to concrete pads or hammered into the ground, and these slot into the post - foxhole has posted something similar. These are unobtrusive as they slot into the centre not fixed around the edge.

The end grain and any horizontal top edge are susceptible to fungal attack.

Make sure you soak all the end grains in preservative - tip the whole can into a bucket and leave the timber in it for at least 15 minutes or so.
Camber the top edge of horizontal timber to avoid standing water

Softwood is prone to a lot of movement of the grain, so don't rely on any surface coating for protection. A penetrative stain or oil is better

 

[kissinger]

Thanks. Reading around, the Sikkens stuff seemed most recommended. I struggled to find a true ‘oil’ product. Even the Ronseal ‘Ultimate Oil’ is water based!

I heard Linseed was a good option but needs a ridiculous number of coats and frequent recoating.