Wooden porch problem

[OldWood]

A friend of mine is building a replacement wooden porch for a small old cottage in central Scotland. It's about 800mm deep from the house wall, and we are having a discussion on what to bed the bottom timbers on.

It's a simple frame structure of two vertical 100mm square timbers on each side and associated cross pieces so the vertical timbers will be end grain to the bricks/concrete that the present porch is sitting on. The timber is larch. One thinking is pads of hardwood - something like oak.

Thanks for any ideas

Rob

 

[MikeG.]

I really would avoid the problem altogether, by doing the traditional thing and having a timber plate lying on the masonry, and then fastening (m&t) the posts into that. The main advantage is that the ends of your posts are then properly and permanently located, and locked to prevent twisting. It would be sheer hard work to achieve this any other way.

All your structural timber should be naturally durable hardwood, and oak is very much the norm in the UK. Chamfered edges to the oak plate helps the rain fall off.

There are traditional ways to do this, and I suggest a drive around some of the older properties in your area to see what has been done.......noting rafter feet details, post shapes and sizes, end of plate details, brackets ("knees") etc etc....if you make this up as you go along it could turn into an unsatisfactory experience.

Please use really small slates or tiles.......there is virtually nothing uglier than a porch with huge tiles.

Mike

 

[bjm]

The heartwood of larch is classified as a 'moderately durable' timber (EN-350) but can be prone to variation depending on age and where it is sourced. Unless you are using posts with a lot of sapwood it should be fine for your intended use. HOWEVER, as for any timber used externally, it is far more important to design-out the possibility of permanent wetting by ensuring that the posts are never sat in a pool of water as this is where problems start. I'd follow the advice Mike gave.


Brian

 

[OldWood]

Thanks guys,

Unfortunately the design has followed as far as I know that of the original and is built as described so end grain downwards is a de facto condition.

Pooling water can certainly be avoided as there is a footing, but something perhaps needs to be added/treated in retrospect to address what seems like a design error !

OW

 

[JanneKi]

Some tips:
- make sure the end grain is saturated with a mix of boiled linseed oil, tar and wood turpentine (with a ratio of 1:1:1) OR outdoor paint (to prevent the end grain "sucking" moisture).
- make sure the end grain piece of wood is not touching directly concrete, i.e. it's up in the air for example with A4-steel brackets + bolts.
- never allow the wood to sit in a puddle of water
- make sure the roof overhangs enough, so that it provides cover for the wood even on a windy and rainy day.
- tilt the floor of the constructions just a little, so that water runs of it freely (like 1 degree).

 

[RogerS]

Can't you set the timber a few mm clear of where the water will be?

 

[cutting42]

Completely OT and apologies but the topic remind me of my favourite joke:

A blonde, wanting to earn some money, decided to hire herself out as a handyman-type and started canvassing a wealthy neighborhood. She went to the front door of the first house and asked the owner if he had any jobs for her to do.

"Well, you can paint my porch. How much will you charge?"

The blonde said, "How about 50 dollars?"

The man agreed and told her that the paint and ladders she would need were in the garage.

The man's wife, inside the house, heard the conversation and said to her husband, "Does she realize that the porch goes all the way around the house?"

The man replied, "She should. She was standing on the porch."

A short time later, the blonde came to the door to collect her money.

"You're finished already?" he asked.

"Yes," the blonde answered, "and I had paint left over, so I gave it two coats."

Impressed, the man reached in his pocket for the $50. "And by the way," the blonde added, "that's not a Porch, it's a Ferrari."